The most common thyroid function tests are:
- Total, or free T4 (the main thyroid hormone in your blood)
- TSH (the hormone from the pituitary gland that stimulates the thyroid to produce T4)
- T3 (the active form of the hormone — T4 is converted to T3)
Other thyroid tests include:
- T3 resin uptake (an older test that is rarely used now)
- Thyroid uptake and scan
- Thyroid binding globulin
- Thyroglobulin
What blood tests do doctors use to check thyroid function?
Doctors may order one or more blood tests to check your thyroid function. Tests may include thyroid-stimulating hormone (TSH), T4, T3, and thyroid antibody tests.
For these tests, a health care professional will draw blood from your arm and send it to a lab for testing. Your doctor will talk to you about your test results.
TSH test
Health care professionals usually check the amount of TSH in your blood first. TSH is a hormone made in the pituitary gland that tells the thyroid how much T4 and T3 to make.
A high TSH level most often means you have hypothyroidism or an underactive thyroid. This means that your thyroid isn’t making enough hormones. As a result, the pituitary keeps making and releasing TSH into your blood.
A low TSH level usually means you have hyperthyroidism or an overactive thyroid. This means that your thyroid is making too much hormone, so the pituitary stops making and releasing TSH into your blood.
If the TSH test results are not normal, you will need at least one other test to help find the cause of the problem.
T4 tests
A high blood level of T4 may mean you have hyperthyroidism. A low level of T4 may mean you have hypothyroidism.
In some cases, high or low T4 levels may not mean you have thyroid problems. If you are pregnant or are taking oral contraceptives NIH external link, your thyroid hormone levels will be higher. Severe illness or using corticosteroids—medicines to treat asthma, arthritis, skin conditions, and other health problems—can lower T4 levels. These conditions and medicines change the number of proteins in your blood that “bind,” or attach, to T4. Bound T4 is kept in reserve in the blood until it’s needed. “Free” T4 is not bound to these proteins and is available to enter body tissues. Because changes in binding protein levels don’t affect free T4 levels, many healthcare professionals prefer to measure free T4.
T3 test
If your health care professional thinks you may have hyperthyroidism even though your T4 level is normal, you may have a T3 test to confirm the diagnosis. Sometimes T4 is normal yet T3 is high, so measuring both T4 and T3 levels can be useful in diagnosing hyperthyroidism.
Thyroid antibody tests
Measuring levels of thyroid antibodies may help diagnose an autoimmune thyroid disorder such as Graves’ disease—the most common cause of hyperthyroidism—and Hashimoto’s disease—the most common cause of hypothyroidism. Thyroid antibodies are made when your immune system attacks the thyroid gland by mistake. Your health care professional may order thyroid antibody tests if the results of other blood tests suggest thyroid disease.
Antithyroglobulin antibody
Thyroglobulin antibody; Thyroiditis – thyroglobulin antibody; Hypothyroidism – thyroglobulin antibody; Thyroiditis – thyroglobulin antibody; Graves disease – thyroglobulin antibody; Underactive thyroid – thyroglobulin antibody
Antithyroglobulin antibody is a test to measure antibodies to a protein called thyroglobulin. This protein is found in thyroid cells.
How The Test Is Performed
A blood sample is needed.
How To Prepare For The Test
You may be told not to eat or drink anything for several hours (usually overnight). Your health care provider may monitor you or tell you to stop taking certain medicines for a short time before the test because they may affect the test results. Never stop taking any medicine without first talking to your provider.
How The Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why The Test Is Performed
This test helps detect possible thyroid problems.
Antithyroglobulin antibodies can be a sign of thyroid gland damage caused by the immune system. They may be measured if thyroiditis is suspected.
Measuring thyroglobulin antibody levels after treatment for thyroid cancer can help your provider decide what the best test is to monitor you for a recurrence of the cancer.
Normal Results
A negative test result is a normal result. It means no antibodies to thyroglobulin are found in your blood.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.
What Abnormal Results Mean
A positive test means antithyroglobulin antibodies are found in your blood. They may be present with:
- Graves disease or overactive thyroid
- Hashimoto thyroiditis
- Subacute thyroiditis
- Underactive thyroid
- Systemic lupus erythematosus
- Type 1 diabetes
Pregnant women and relatives of those with autoimmune thyroiditis may also test positive for these antibodies.
Risks
Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
Antithyroid microsomal antibody
Thyroid anti microsomal antibody; Antimicrosomal antibody; Microsomal antibody; Thyroid peroxidase antibody; TPOAb
Microsomes are found inside thyroid cells. The body produces antibodies to microsomes when there has been damage to thyroid cells. The antithyroid microsomal antibody test measures these antibodies in the blood.
How The Test Is Performed
A blood sample is needed.
How The Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why The Test Is Performed
This test is done to confirm the cause of thyroid problems, including Hashimoto thyroiditis .
The test is also used to find out if an immune or autoimmune disorder is damaging the thyroid.
Normal Results
A negative test means the result is normal.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens. Talk to your health care provider about the meaning of your specific test results.
What Abnormal Results Mean
A positive test may be due to:
- Granulomatous thyroiditis
- Hashimoto thyroiditis
High levels of these antibodies have also been linked with an increased risk of:
- Miscarriage
- Preeclampsia
- Premature birth
- In vitro fertilization failure
Important: A positive result does not always mean that you have a thyroid condition or that you need treatment for your thyroid. A positive result may mean that you have a higher chance of developing thyroid disease in the future.
Antithyroid microsomal antibodies may be seen in your blood if you have other autoimmune conditions, including:
- Autoimmune hemolytic anemia
- Autoimmune hepatitis
- Autoimmune adrenal disease
- Rheumatoid arthritis
- Sjögren syndrome
- Systemic lupus erythematosus
Risks
Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
Fine needle aspiration of the thyroid
Thyroid nodule fine needle aspirate biopsy; Biopsy – thyroid – skinny-needle; Skinny-needle thyroid biopsy; Thyroid nodule – aspiration; Thyroid cancer – aspiration
Fine needle aspiration of the thyroid gland is a procedure to remove thyroid cells for examination. The thyroid gland is a butterfly-shaped gland located inside the front of the lower neck.
How The Test Is Performed
This test may be done in the health care provider’s office or in a hospital. Numbing medicine (anesthesia) may or may not be used. Because the needle is very thin, you may not need this medicine.
You lie on your back with a pillow under your shoulders with your neck extended. The biopsy site is cleaned. A thin needle is inserted into your thyroid, where it collects a sample of thyroid cells and fluid. The needle is then taken out. If the provider cannot feel the biopsy site, they may use ultrasound or a CT scan to guide where to put the needle. Ultrasound and CT scans are painless procedures that show images inside the body.
Pressure is applied to the biopsy site to stop any bleeding. The site is then covered with a bandage.
How To Prepare For The Test
Tell your provider if you have drug allergies , bleeding problems, or are pregnant. Also, make sure your provider has a current list of all medicines you take, including herbal remedies and over-the-counter drugs.
A few days to a week before your biopsy, you may be asked to stop taking medicines that make it harder for your blood to clot. Talk with your provider before stopping any drugs. The drugs you may need to stop taking include:
- Aspirin
- Clopidogrel (Plavix)
- Ibuprofen (Advil, Motrin)
- Naproxen (Aleve, Naprosyn)
- Warfarin (Coumadin)
How The Test Will Feel
If numbing medicine is used, you may feel a sting as the needle is inserted and the medicine is injected.
As the biopsy needle passes into your thyroid, you may feel some pressure, but it should not be painful.
You may have slight discomfort in your neck afterward. You may also have slight bruising, which soon goes away.
Why The Test Is Performed
This is a test to diagnose thyroid disease or thyroid cancer . It is often used to find out if thyroid nodules that your provider can feel or seen on an ultrasound are noncancerous or cancerous.
Normal Results
A normal result shows the thyroid tissue looks normal and the cells do not appear to be cancer under a microscope.
What Abnormal Results Mean
Abnormal results may mean:
- Thyroid disease such as goiter or thyroiditis
- Noncancerous tumors
- Thyroid cancer
Risks
The main risk is bleeding into or around the thyroid gland. With severe bleeding, there may be pressure on the windpipe (trachea). This problem is rare.
Thyroid ultrasound
Ultrasound – thyroid; Thyroid sonogram; Thyroid echogram
A thyroid ultrasound is an imaging method to see the thyroid, a gland in the neck that regulates metabolism .
How The Test Is Performed
Ultrasound is a painless method that uses sound waves to create images of the inside of the body. The test is usually done in the ultrasound or radiology department. It also can be done in a clinic.
The test is done in this way:
- You lie down with your neck on a pillow or other soft support. Your neck is stretched slightly.
- The ultrasound technician applies a water-based gel on your neck to help with transmit the sound waves.
- Next, the technician moves a wand, called a transducer, back and forth over the area. The transducer gives off sound waves. The sound waves go through your body and bounce off the area being studied (in this case, the thyroid gland). A computer looks at the pattern that the sound waves create when bouncing back, and creates an image from them.
How To Prepare For The Test
No special preparation is necessary for this test.
How The Test Will Feel
You should feel very little discomfort with this test. The gel may be cold.
Why The Test Is Performed
A thyroid ultrasound is usually done when physical exam shows any of these findings:
- You have a growth on your thyroid gland, called a thyroid nodule .
- The thyroid feels big or irregular, called a goiter .
- You have abnormal lymph nodes near your thyroid.
Ultrasound is also often used to guide the needle in biopsies of:
- Thyroid nodules or the thyroid gland . In this test, a needle draws out a small amount of tissue from the nodule or thyroid gland. This is a test to diagnose thyroid disease or thyroid cancer.
- The parathyroid gland.
Normal Results
A normal result will show that the thyroid has a normal size, shape, and position.
What Abnormal Results Mean
Abnormal results may be due to:
- Cysts
- Enlargement of the thyroid gland ( goiter )
- Thyroid nodules
- Thyroiditis, or inflammation of the thyroid (if a biopsy is done)
- Thyroid cancer (if a biopsy is done)
Your health care provider can use these results and the results of other tests to direct your care.
Risks
There are no documented risks of ultrasound.
T3RU test
Resin T3 uptake; T3 resin uptake; Thyroid hormone-binding ratio
The T3RU test measures the level of proteins that carry thyroid hormone in the blood. This can help your health care provider interpret the results of T3 and T4 blood tests.
Because tests called the free T4 blood test and TBG blood tests are now available, the T3RU test is rarely used these days.
How The Test Is Performed
A blood sample is needed.
How To Prepare For The Test
Your provider will tell you if you need to stop taking any medicines before the test that may affect your test result. DO NOT stop taking any medicine without first talking to your provider.
Some drugs that can increase T3RU levels include:
- Anabolic steroids
- Heparin
- Phenytoin
- Salicylates (high dose)
- Warfarin
Some drugs that can decrease T3RU levels include:
- Antithyroid medicines
- Birth control pills
- Clofibrate
- Estrogen
- Thiazides
Pregnancy can also decrease T3RU levels.
These things can increase thyroxin binding globulin (TBG) levels (see below section “Why the Test is Performed” for more about TBG):
- Male hormones (androgens)
- Serious illness
- Kidney disease
Other medicines that bind to protein in the blood can also affect test results
How The Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why The Test Is Performed
This test is done to check your thyroid function. Thyroid function depends on the action of many different hormones, including thyroid-stimulating hormone (TSH), T3, and T4.
This test helps see how much thyroxin binding globulin (TBG) is available. TBG is a protein that carries most of the T3 and T4 in the blood.
Your provider may recommend a T3RU test if you have signs of a thyroid disorder, including:
- Hyperthyroidism (overactive thyroid)
- Hypothyroidism (underactive thyroid)
- Thyrotoxic periodic paralysis (muscle weakness caused by high levels of thyroid hormone in the blood)
Normal Results
Normal values range from 24% to 37%.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.
What Abnormal Results Mean
Higher-than-normal levels may indicate:
- Kidney failure
- Overactive thyroid (hyperthyroidism)
- Nephrotic syndrome
- Protein malnutrition
lower-than-normal levels may indicate:
- Acute hepatitis (liver disease)
- Pregnancy
- Hypothyroidism
- Use of estrogen
Abnormal results may also be due to an inherited condition of high TBG levels. Usually, thyroid function is normal in people with this condition.
This test may also be done for:
- Chronic thyroiditis (swelling or inflammation of the thyroid gland, including Hashimoto’s disease)
- Drug-induced hypothyroidism
- Graves disease
- Subacute thyroiditis
- Thyrotoxic periodic paralysis
- Toxic nodular goiter
Risks
Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
Fine needle aspiration of the thyroid
Thyroid nodule fine needle aspirate biopsy; Biopsy – thyroid – skinny-needle; Skinny-needle thyroid biopsy; Thyroid nodule – aspiration; Thyroid cancer – aspiration
Fine needle aspiration of the thyroid gland is a procedure to remove thyroid cells for examination. The thyroid gland is a butterfly-shaped gland located inside the front of the lower neck.
How The Test Is Performed
This test may be done in the health care provider’s office or in a hospital. Numbing medicine (anesthesia) may or may not be used. Because the needle is very thin, you may not need this medicine.
You lie on your back with a pillow under your shoulders with your neck extended. The biopsy site is cleaned. A thin needle is inserted into your thyroid, where it collects a sample of thyroid cells and fluid. The needle is then taken out. If the provider cannot feel the biopsy site, they may use an ultrasound or a CT scan to guide where to put the needle. Ultrasound and CT scans are painless procedures that show images inside the body.
Pressure is applied to the biopsy site to stop any bleeding. The site is then covered with a bandage.
How To Prepare For The Test
Tell your provider if you have drug allergies, bleeding problems, or are pregnant. Also, make sure your provider has a current list of all medicines you take, including herbal remedies and over-the-counter drugs.
A few days to a week before your biopsy, you may be asked to stop taking medicines that make it harder for your blood to clot. Talk with your provider before stopping any drugs. The drugs you may need to stop taking include:
- Aspirin
- Clopidogrel (Plavix)
- Ibuprofen (Advil, Motrin)
- Naproxen (Aleve, Naprosyn)
- Warfarin (Coumadin)
How The Test Will Feel
If numbing medicine is used, you may feel a sting as the needle is inserted and the medicine is injected.
As the biopsy needle passes into your thyroid, you may feel some pressure, but it should not be painful.
You may have slight discomfort in your neck afterward. You may also have slight bruising, which soon goes away.
Why The Test Is Performed
This is a test to diagnose thyroid disease or thyroid cancer . It is often used to find out if thyroid nodules that your provider can feel or seen on an ultrasound are noncancerous or cancerous.
Normal Results
A normal result shows the thyroid tissue looks normal and the cells do not appear to be cancer under a microscope.
What Abnormal Results Mean
Abnormal results may mean:
- Thyroid diseases such as goiter or thyroiditis
- Noncancerous tumors
- Thyroid cancer
Risks
The main risk is bleeding into or around the thyroid gland. With severe bleeding, there may be pressure on the windpipe (trachea). This problem is rare.
Antithyroid microsomal antibody
Thyroid anti microsomal antibody; Antimicrosomal antibody; Microsomal antibody; Thyroid peroxidase antibody; TPOAb
Microsomes are found inside thyroid cells. The body produces antibodies to microsomes when there has been damage to thyroid cells. The antithyroid microsomal antibody test measures these antibodies in the blood.
How The Test Is Performed
A blood sample is needed.
How The Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why The Test Is Performed
This test is done to confirm the cause of thyroid problems, including Hashimoto thyroiditis.
The test is also used to find out if an immune or autoimmune disorder is damaging the thyroid.
Normal Results
A negative test means the result is normal.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens. Talk to your health care provider about the meaning of your specific test results.
What Abnormal Results Mean
A positive test may be due to:
- Granulomatous thyroiditis
- Hashimoto thyroiditis
High levels of these antibodies have also been linked with an increased risk of:
- Miscarriage
- Preeclampsia
- Premature birth
- In vitro fertilization failure
Important: A positive result does not always mean that you have a thyroid condition or that you need treatment for your thyroid. A positive result may mean that you have a higher chance of developing thyroid disease in the future.
Antithyroid microsomal antibodies may be seen in your blood if you have other autoimmune conditions, including:
- Autoimmune hemolytic anemia
- Autoimmune hepatitis
- Autoimmune adrenal disease
- Rheumatoid arthritis
- Sjögren syndrome
- Systemic lupus erythematosus
Risks
Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
Thyroid scan
Scan – thyroid; Radioactive iodine uptake and scan test – thyroid; Nuclear scan – thyroidA thyroid scan uses a radioactive iodine tracer to examine the structure and function of the thyroid gland. This test is often done together with a radioactive iodine uptake test .
How The Test Is Performed
The test is done in this way:
- You are given a pill that contains a tiny amount of radioactive iodine. After swallowing it, you wait as the iodine collects in your thyroid.
- The first scan is usually done 4 to 6 hours after you take the iodine pill. Another scan is usually done 24 hours later. During the scan, you lie on your back on a movable table. Your neck and chest are positioned under the scanner. You must lie still so that the scanner gets a clear image.
The scanner detects the location and intensity of the rays given off by the radioactive material. A computer displays images of the thyroid gland. Other scans use a substance called technetium instead of radioactive iodine.
How To Prepare For The Test
Follow instructions about not eating before the test. You may be told not to eat after midnight the night before your scan.
Tell your health care provider if you are taking anything that contains iodine because it may affect your test results. This includes some medicines, including thyroid drugs. Supplements such as kelp also contain iodine.
Also tell your provider if you have:
- Diarrhea (may decrease absorption of the radioactive iodine)
- Had recent CT scans using intravenous or oral iodine-based contrast (within the past 2 weeks)
- Too little or too much iodine in your diet
Remove jewelry, dentures, or other metals because they may interfere with the image.
How The Test Will Feel
Some people find it uncomfortable to stay still during the test.
Why The Test Is Performed
This test is done to:
- Evaluate thyroid nodules or goiter
- Find the cause of an overactive thyroid gland
- Check for thyroid cancer (rarely, since other tests are more accurate for this)
Normal Results
Normal test results will show that the thyroid appears to be the correct size, shape, and in the proper location. It is an even gray color on the computer image without darker or lighter areas.
What Abnormal Results Mean
A thyroid that is enlarged or pushed off to one side could be a sign of a tumor .
Nodules absorb more or less iodine and this will make them look darker or lighter on the scan. A nodule is usually lighter if it has not taken up the iodine. If part of the thyroid appears lighter, it could be a thyroid problem. Nodules that are darker have taken up more iodine. They can be overactive and may be the cause of an overactive thyroid.
The computer will also show the percentage of iodine that has collected in your thyroid gland (radioiodine uptake). If your gland collects too much iodine, it may be due to an overactive thyroid. If your gland collects too little iodine, it may be due to an underactive thyroid.
Risks
All radiation has possible side effects. The amount of radioactivity is very small, and there have been no documented side effects. The amount of iodine used is less than the amount in a normal diet.
People with an allergy to iodine in the diet or to shellfish may not be able to have this test. You may be able to have this test if you have an allergy to the iodine in the contrast dye.
Women who are pregnant or breastfeeding should not have this test.
Talk to your provider if you have concerns about this test.
Considerations
The radioactive iodine leaves your body through your urine. You may need to take special precautions, such as flushing twice after urinating, for 24 to 48 hours after the test. Ask your provider or the radiology/nuclear medicine team performing the scan about taking precautions.
Thyroid ultrasound
Ultrasound – thyroid; Thyroid sonogram; Thyroid echogram
A thyroid ultrasound is an imaging method to see the thyroid, a gland in the neck that regulates metabolism .
How The Test Is Performed
Ultrasound is a painless method that uses sound waves to create images of the inside of the body. The test is usually done in the ultrasound or radiology department. It also can be done in a clinic.
The test is done in this way:
- You lie down with your neck on a pillow or other soft support. Your neck is stretched slightly.
- The ultrasound technician applies a water-based gel on your neck to help transmit the sound waves.
- Next, the technician moves a wand, called a transducer, back and forth over the area. The transducer gives off sound waves. The sound waves go through your body and bounce off the area being studied (in this case, the thyroid gland). A computer looks at the pattern that the sound waves create when bouncing back and creates an image from them.
How To Prepare For The Test
No special preparation is necessary for this test.
How The Test Will Feel
You should feel a very little discomfort with this test. The gel may be cold.
Why The Test Is Performed
A thyroid ultrasound is usually done when a physical exam shows any of these findings:
- You have a growth on your thyroid gland, called a thyroid nodule.
- The thyroid feels big or irregular, called a goiter.
- You have abnormal lymph nodes near your thyroid.
Ultrasound is also often used to guide the needle in biopsies of:
- Thyroid nodules or the thyroid gland. In this test, a needle draws out a small amount of tissue from the nodule or thyroid gland. This is a test to diagnose thyroid disease or thyroid cancer.
- The parathyroid gland.
Normal Results
A normal result will show that the thyroid has a normal size, shape, and position.
What Abnormal Results Mean
Abnormal results may be due to:
- Cysts
- Enlargement of the thyroid gland ( goiter )
- Thyroid nodules
- Thyroiditis, or inflammation of the thyroid (if a biopsy is done)
- Thyroid cancer (if a biopsy is done)
Your health care provider can use these results and the results of other tests to direct your care.
Risks
There are no documented risks of ultrasound
TSH test
Thyrotropin; Thyroid-stimulating hormone; Hypothyroidism – TSH; Hyperthyroidism – TSH; Goiter – TSH
A TSH test measures the amount of thyroid-stimulating hormone (TSH) in your blood. TSH is produced by the pituitary gland. It tells the thyroid gland to make and release thyroid hormones into the blood.
How The Test Is Performed
A blood sample is needed. Other thyroid tests that may be done at the same time include:
- T3 test (free or total)
- T4 test (free or total)
How To Prepare For The Test
There is no preparation needed for this test. Ask your health care provider about any medicines you are taking that may affect the test results. DO NOT stop taking any medicines without first asking your provider.
Medicines you may need to stop for a short time include:
- Amiodarone
- Dopamine
- Lithium
- Potassium iodide
- Prednisone or other glucocorticoid medicines
How The Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why The Test Is Performed
Your provider will order this test if you have symptoms or signs of an overactive or underactive thyroid gland. It is also used to monitor the treatment of these conditions.
Your provider may also check your TSH level if you are planning to get pregnant.
Normal Results
Normal values range from 0.4 to 4.0 milli-international units per liter (mIU/L).
- TSH values can vary during the day. It is best to have the test early in the morning.
- Experts do not fully agree on what the upper number should be. Opinions vary from 2.5 to 4.0 mIU/L.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.
If you are being treated for a thyroid disorder, your TSH level will likely be kept between 0.5 and 4.0 mIU/L, except when:
- A pituitary disorder is the cause of the thyroid problem. A low TSH may be expected.
- Someone has been treated for thyroid cancer. A low TSH may be best to prevent thyroid cancer from coming back.
- A woman is pregnant. The normal range for TSH is different for women who are pregnant. Your provider may suggest that you take thyroid hormone, even if your TSH is in the normal range.
What Abnormal Results Mean
A higher-than-normal TSH level is most often due to an underactive thyroid gland ( hypothyroidism ). There are many causes of this problem.
A lower-than-normal level may be due to an overactive thyroid gland, which can be caused by:
- Graves disease
- Toxic nodular goiter or multinodular goiter
- Too much iodine in the body (due to receiving iodine contrast used during imaging tests, such as CT scan)
- Taking too much thyroid hormone medicine or prescribed natural or over-the-counter supplements that contain thyroid hormone
Use of certain medicines may also cause a lower-than-normal TSH level. These include glucocorticoids/steroids, dopamine, certain chemotherapy drugs, and opioid painkillers such as morphine.
Risks
Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
TSI test
TSH receptor stimulating antibody; Thyroid stimulating immunoglobulin; Hypothyroidism – TSI; Hyperthyroidism – TSI; Goiter – TSI; Thyroiditis – TSI
TSI stands for thyroid-stimulating immunoglobulin. TSIs are antibodies that tell the thyroid gland to become more active and release excess amounts of thyroid hormone into the blood. A TSI test measures the amount of thyroid-stimulating immunoglobulin in your blood.
How The Test Is Performed
A blood sample is needed.
How To Prepare For The Test
No special preparation is usually necessary.
How The Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why The Test Is Performed
Your health care provider may recommend this test if you have signs or symptoms of an overactive thyroid (hyperthyroidism), including symptoms of:
- Graves disease
- Toxic multinodular goiter
- Thyroiditis (swelling of the thyroid gland caused by an overactive immune system)
The test is also done during the last 3 months of pregnancy to predict Graves disease in the baby.
The TSI test is most commonly done if you have signs or symptoms of hyperthyroidism but are unable to have a test called thyroid uptake and scan.
Normal Results
Normal values are less than 130% of basal activity.
Normal value ranges may vary slightly among different laboratories. Some laboratories use different measurements or may test different specimens. Talk to your provider about the meaning of your specific test results.
What Abnormal Results Mean
A higher-than-normal level may indicate:
- Graves disease (most common)
- Hashitoxicosis (very rare)
- Neonatal thyrotoxicosis
Risks
Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
Antithyroglobulin antibody
Thyroglobulin antibody; Thyroiditis – thyroglobulin antibody; Hypothyroidism – thyroglobulin antibody; Thyroiditis – thyroglobulin antibody; Graves disease – thyroglobulin antibody; Underactive thyroid – thyroglobulin antibody
Antithyroglobulin antibody is a test to measure antibodies to a protein called thyroglobulin. This protein is found in thyroid cells.
How The Test Is Performed
A blood sample is needed.
How To Prepare For The Test
You may be told not to eat or drink anything for several hours (usually overnight). Your health care provider may monitor you or tell you to stop taking certain medicines for a short time before the test because they may affect the test results. Never stop taking any medicine without first talking to your provider.
How The Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why The Test Is Performed
This test helps detect possible thyroid problems.
Antithyroglobulin antibodies can be a sign of thyroid gland damage caused by the immune system. They may be measured if thyroiditis is suspected.
Measuring thyroglobulin antibody levels after treatment for thyroid cancer can help your provider decide what the best test is to monitor you for a recurrence of cancer.
Normal Results
A negative test result is a normal result. It means no antibodies to thyroglobulin are found in your blood.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.
What Abnormal Results Mean
A positive test means antithyroglobulin antibodies are found in your blood. They may be present with:
- Graves disease or overactive thyroid
- Hashimoto thyroiditis
- Subacute thyroiditis
- Underactive thyroid
- Systemic lupus erythematosus
- Type 1 diabetes
Pregnant women and relatives of those with autoimmune thyroiditis may also test positive for these antibodies.
Risks
Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
Free T4 test
Thyroxine test; Total T4 test
T4 (thyroxine) is the main hormone produced by the thyroid gland. A laboratory test can be done to measure the amount of free T4 in your blood.
How The Test Is Performed
A blood sample is needed.
How To Prepare For The Test
Your health care provider will tell you if you need to stop taking any medicines that may affect the test result. In general, test results are not affected by other medicines you may be taking.
Pregnancy and some diseases, including kidney and liver disease, can affect the results of this test.
How The Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why The Test Is Performed
Your provider may recommend this test if you have signs of a thyroid disorder, including:
- Abnormal findings of other thyroid blood tests, such as TSH or T3
- Symptoms of an overactive thyroid
- Symptoms of an underactive thyroid
- Hypopituitarism (the pituitary gland does not produce enough of its hormones)
- Lump or nodule in the thyroid
- The enlarged or irregular thyroid gland
- Problems becoming pregnant
This test is also used to monitor people who are being treated for thyroid problems.
Normal Results
A typical normal range is 4.5 to 11.2 micrograms per deciliter (mcg/dL) or 57919.50 to 144155.20 picomoles per liter (picomol/L).
Normal value ranges may vary slightly among different laboratories. Some laboratories use different measurements or may test different specimens. Talk to your provider about the meaning of your specific test results.
What Abnormal Results Mean
To fully understand results of the free T4 test, results of other thyroid blood tests, such as TSH or T3, may be needed.
Test results may also be affected by pregnancy, estrogen level, liver problems, more severe body-wide illnesses, and inherited changes in a protein that binds T4.
A higher than normal level of T4 may be due to conditions that involve an overactive thyroid, including:
- Graves disease
- Taking too much thyroid hormone medicine
- Thyroiditis
- Toxic goiter or toxic thyroid nodules
- Some tumors of the testes or ovaries (rare)
- Getting medical imaging tests with contrast dye that contains iodine (rare, and only if there is a problem with the thyroid)
- Eating a lot of foods that contain iodine (very rare, and only if there is a problem with the thyroid)
A lower than normal level of T4 may be due to:
- Hypothyroidism (including Hashimoto’s disease and other disorders involving an underactive thyroid)
- Severe acute illness
- Malnutrition or fasting
- Use of certain medicines
Risks
Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
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