Antidiuretic blood test measures the level of antidiuretic hormone (ADH) in blood.
How the Test is Performed
A blood sample is needed .
How to Prepare for the Test
Talk to your doctor about your medicines before the test. Many drugs can affect ADH level, including:
- Alcohol
- Diuretics (water pills)
- Blood pressure medicines
- Insulin
- Medicines for mental disorders
- Nicotine
- Steroids
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 slight bruising. This soon goes away.
Why the Test is Performed
ADH is a hormone that is produced in a part of the brain called the hypothalamus. It is then stored and released from the pituitary, a small gland at the base of the brain. ADH acts on the kidneys to control the amount of water excreted in the urine.
ADH blood test is ordered when your health care provider suspects you have a disorder that affects your ADH level such as:
- The buildup of fluids in your body that are causing swelling or puffiness ( edema )
- Excessive amounts of urine
- Low sodium (salt) level in your blood
- The thirst that is intense or uncontrollable
Certain diseases affect the normal release of ADH. The blood level of ADH must be tested to determine the cause of the disease. ADH may be measured as part of a water restriction test to find the cause of a disease.
Normal Results
Normal values for ADH can range from 1 to 5 pg/mL.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
A higher-than-normal level may occur when too much ADH is released, either from the brain where it is made, or from somewhere else in the body. This is called syndrome of inappropriate ADH (SIADH).
Causes of SIADH include:
- Brain injury or trauma
- Brain tumors
- Fluid imbalance after surgery
- Infection in the brain or the tissue that surrounds the brain
- Infection in the lungs
- Small cell carcinoma lung cancer
- Stroke
A lower-than-normal level may indicate:
- Damage to the hypothalamus or pituitary gland
- Diabetes insipidus . A condition in which the kidneys are not able to conserve water.
- Excessive thirst ( polydipsia )
- Too much fluid in the body (volume overload)
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 accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
