Definition

The antidiuretic blood test measures the level of antidiuretic hormone (ADH) in blood.

Alternative Names

Arginine vasopressin; Antidiuretic hormone; AVP; Vasopressin

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

Talk to your health care provider about your medicines before the test. Many medicines 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 regulate the amount of water excreted in the urine.

The ADH blood test is ordered when your provider suspects you have a disorder that may be due to an abnormal ADH level such as:

• Buildup of fluids in your body that are causing swelling or puffiness (edema)
• Excessive amounts of urine
• Low sodium (salt) level in your blood
• 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 0 to 5.9 pg/mL (0 to 5.4 pmol/L).

Normal value ranges may vary slightly among different labs. Some labs use different measurements or may test different specimens. Talk to your provider about the meaning of your specific test results.

Most labs cannot run this test. Only very specialized labs can perform the assay correctly.

Serum co-peptin is now commonly used as a substitute for measuring ADH.

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 the syndrome of inappropriate ADH (SIADH).

There are many reasons why your body may make too much ADH. Common situations when ADH is released into the blood when it should not be produced include:

• Medicines, such as certain seizure medicines, antidepressants, cancer medicines, opiates (less often), and heart, diabetes, and blood pressure medicines
• Surgery under general anesthesia
• Disorders of the brain, such as injury, infections, and stroke
• Brain surgery in the region of the hypothalamus
• Removal of a noncancerous (benign) pituitary tumor
• Tuberculosis
• Cancer (especially small cell cancer of the lung)
• Lung disease, such as pneumonia
• Substance use disorder

A higher-than-normal level of ADH may be found in people with heart failure, liver failure, or some kind of kidney disease.

A lower-than-normal level may indicate:

• Damage to the hypothalamus or pituitary gland
• Central diabetes insipidus (a condition in which the kidneys are not able to conserve water)
• Excessive thirst (polydipsia)
• Too much fluid in the blood vessels (volume overload)

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Taking blood 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
• Multiple punctures to locate veins
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

Christ-Crain M, Thompson CJ, Verbalis JG. Posterior pituitary. In: Melmed S, Auchus RJ, Goldfine AB, Rosen CJ, Kopp PA, eds. Williams Textbook of Endocrinology. 15th ed. Philadelphia, PA: Elsevier; 2025:chap 8.

Oh MS, Briefel G, Pincus MR. Evaluation of renal function, water, electrolytes, and acid-base balance. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 15.

Soto-Rivera CL, Breault DT, Majzuob JA. Other abnormalities of arginine vasopressin metabolism and action. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 597.

Verbalis JG. Disorders of water balance. In: Yu ASL, Chertow GM, Luyckx VA, Marsden PA, Skorecki K, Taal MW, eds. Brenner and Rector's The Kidney. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 15.

Verbalis JG. Posterior pituitary. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 206.