Oral Glucose Tolerance Test – Indications, Procedures, Results

Last updated: February 8, 2026Reviewed date: February 8, 2026Reading time: 4 min read
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Oral glucose tolerance test - non-pregnant; OGTT - non-pregnant; Diabetes - glucose tolerance test; Diabetic - glucose tolerance test The glucose tolerance test is a lab test to check how your body breaks down sugar. Tests to screen for diabetes during pregnancy are done differently. How...

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Article Summary

Oral glucose tolerance test - non-pregnant; OGTT - non-pregnant; Diabetes - glucose tolerance test; Diabetic - glucose tolerance test The glucose tolerance test is a lab test to check how your body breaks down sugar. Tests to screen for diabetes during pregnancy are done differently. How the Test is Performed The most common glucose tolerance test is the oral glucose tolerance test (OGTT). Before the test...

Key Takeaways

  • This article explains How the Test is Performed in simple medical language.
  • This article explains How to Prepare for the Test in simple medical language.
  • This article explains How the Test will Feel in simple medical language.
  • This article explains Why the Test is Performed in simple medical language.
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Definition

Oral glucose tolerance test – non-pregnant; OGTT – non-pregnant; insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">Diabetes – glucose tolerance test; Diabetic – glucose tolerance test

The glucose tolerance test is a lab test to check how your body breaks down sugar.

Tests to screen for insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes during pregnancy are done differently.

How the Test is Performed

The most common glucose tolerance test is the oral glucose tolerance test (OGTT).

Before the test begins, a sample of blood will be taken.

You will then be asked to drink a liquid containing a certain amount of glucose (usually 75 grams). Your blood will be taken again every 30 to 60 minutes after you drink the solution.

The test may take up to 3 hours.

A similar test is the intravenous (IV) glucose tolerance test (IGTT). It is rarely used, and is never used to diagnose insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes. With IGTT, glucose is injected into your vein for 3 minutes. Blood insulin levels are measured before the injection, and again at 1 and 3 minutes after the injection. The timing may vary.

How to Prepare for the Test

Make sure you eat normally for several days before the test.

DO NOT eat or drink anything for at least 8 hours before the test. You cannot eat during the test.

Ask your health care provider if any of the medicines you take can affect the test results.

How the Test will Feel

Drinking the glucose solution is similar to drinking very sweet soda.

Serious side effects from this test are very uncommon. With the blood test, some people feel nauseated, sweaty, lightheaded, or may even feel short of breath or faint after drinking the glucose. Tell your doctor if you have a history of these symptoms related to blood tests or medical procedures.

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

Glucose is the sugar the body uses for energy. People with untreated insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes have high blood glucose levels.

Most often, the first tests used to diagnose insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes in people who are not pregnant are:

  • Fasting blood glucose level: insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes is diagnosed if it is higher than 126 mg/dL (7 mmol/L) on 2 different tests
  • Hemoglobin A1c test: insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes is diagnosed if the test result is 6.5% or higher

Glucose tolerance tests are also used to diagnose insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes. The OGTT is used to screen for, or diagnose diabetes in people with a fasting blood glucose level that is high, but is not high enough (above 125 mg/dL or 7 mmol/L) to meet the diagnosis for diabetes.

Normal Results

Normal blood values for a 75 gram OGTT used to check for type 2 insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes in those who are not pregnant:

  • Fasting: 60 to 100 mg/dL (3.3 to 5.5 mmol/L)
  • 1 hour: less than 200 mg/dL (11.1 mmol/L)
  • 2 hours: less than 140 mg/dL (7.8 mmol/L)

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

A glucose level that is higher than normal may mean you have pre-insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes or diabetes:

  • A 2 hour value between 140 and 200 mg/dL (7.8 and 11.1 mmol/L) is called impaired glucose tolerance. Your doctor may call this “pre-insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes.” It means you are at increased risk of developing diabetes over time.
  • A glucose level of 200 mg/dL (11.1 mmol/L) or higher is used to diagnose insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes.

Serious stress to the body, such as from trauma, stroke, heart attack, or surgery, can raise your blood glucose level. Vigorous exercise can lower your blood glucose level.

Some medicines can raise or lower your blood glucose level. Before having the test, tell your provider about any medicines you are taking.

Risks

You may have some of the symptoms listed above under the heading titled “How the Test will Feel.”

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 accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)
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Which doctor may help?

Start with a registered doctor or the nearest qualified health center.

What to tell the doctor

  • Write when the problem started and how it changed.
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Safe first steps

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  • Do not take random painkillers to hide chest pain before medical evaluation.

Avoid these mistakes

  • Do not start antibiotics without a proper medical decision.
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  • Do not delay emergency care because of home remedies.

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Tests to discuss with doctor
  • Basic vital signs: temperature, pulse, blood pressure, oxygen level if needed
  • Relevant blood, urine, imaging, or specialist tests only after clinical assessment
Questions to ask
  • What is the most likely cause of my symptoms?
  • Which warning signs mean I should go to emergency care?
  • Which tests are really needed now?
  • Which medicines are safe for my age, pregnancy status, allergy, kidney/liver/stomach condition, and current medicines?

Emergency warning signs such as chest pain, severe breathing difficulty, sudden weakness, confusion, severe dehydration, major injury, or loss of bladder/bowel control need urgent medical care. Do not wait for online information.

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Care roadmap for: Oral Glucose Tolerance Test – Indications, Procedures, Results

Use this simple roadmap to understand the next safe steps. It is educational and does not replace examination by a doctor.

Go to emergency care if you notice:
  • Severe or rapidly worsening symptoms
  • Breathing difficulty, chest pain, fainting, confusion, severe weakness, major injury, or severe dehydration
Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.
  1. Step 1

    Check danger signs first

    If danger signs are present, seek emergency care and do not wait for online information.

  2. Step 2

    Record the symptom story

    Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.

  3. Step 3

    Visit a qualified clinician

    A doctor, nurse, or qualified healthcare provider can examine you and decide which tests or treatment are needed.

  4. Step 4

    Do only useful tests

    Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.

  5. Step 5

    Follow up and return early if worse

    If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips
  • Take a written symptom diary and all previous prescriptions/test reports.
  • Do not hide medicines already taken, even herbal or over-the-counter medicines.
  • Ask which warning signs mean urgent referral to hospital.

This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.

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