DefinitionADH is a test that measures the amount of antidiuretic hormone (ADH) in blood. 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 gland, a small gland at the base of the brain.ADH helps manage the amount of water in the body by acting on the kidneys.
Alternative NamesArginine vasopressin; Antidiuretic hormone; AVP; Vasopressin
How the test is performedA blood sample is needed. For information on how this is done, see: Venipuncture
How to prepare for the testTalk to your health care provider about your medications before the test. Many medications can affect ADH measurements, including:AlcoholClonidineDiureticsHaloperidolInsulinLithiumMorphineNicotineSteroids
How the test will feelWhen the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performedThis test is performed if your health care provider suspects you have a disorder that affects your ADH level. ADH helps manage the amount of water in the body by acting on the kidneys.Your health care provider may order ADH levels if you have:Buildup of fluids in your body that are causing swelling or puffinessExcessive amounts of urineLow sodium ("salt") levels in your bloodThirst that is intense or uncontrollableCertain 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 ValuesNormal values for ADH can range from 1 - 5 pg/mLNote: pg/mL = picograms per milliliterThe 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 may test different specimens. Talk to your doctor about the meaning of your specific test results.
What abnormal results meanHigher-than-normal levels 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 traumaBrain tumorsFluid imbalance after surgeryInfection in the brain or the tissue that surrounds the brainInfection in the lungsSmall cell carcinoma lung cancerStrokeLower-than-normal levels may indicate:Damage to the pituitary glandDiabetes insipidus -- a condition in which the kidneys are not able to conserve waterPrimary polydipsia
What the risks areVeins and arteries vary in size from one patient 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 bleedingFainting or feeling light-headedHematoma (blood accumulating under the skin)Infection (a slight risk any time the skin is broken)
ReferencesRobinson AG, Verbalis JG. Posterior pituitary. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 10.