Antidiuretic Hormone

Does this test have other names?

Vasopressin, arginine vasopressin, ADH

What is this test?

This test measures how much antidiuretic hormone (ADH) is in your blood.

ADH is made by your hypothalamus. ADH keeps the amount of water in your body in balance. Certain conditions can affect the amount of ADH that your body makes. These include hyponatremia, or low sodium levels in your bodily fluids. They also include diabetes insipidus. Symptoms of this condition include urinating often and being very thirsty.

Why do I need this test?

You may have this test if your healthcare provider thinks you have a problem that affects your ADH levels. 

What other tests might I have along with this test?

Your healthcare provider may also order other tests, including a water deprivation test. In this test, you stop drinking fluids for several hours. Then your urine and blood are measured to see how many solid particles they have.

Your provider may also order a water loading test. In this test, you drink certain amounts of water. Then your provider measures the water levels in your urine over time.

You might need an MRI to see if there are any problems with the hypothalamus or pituitary gland.

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

Normal ADH levels in adults vary but are usually less than 2.5 pg/mL.

Higher than normal results may mean that you have a condition called syndrome of inappropriate antidiuretic hormone (SIADH). It causes your body to hold onto too much water instead of getting rid of it in your urine. SIADH may be caused by lung tumors, central nervous system tumors, or a fluid problem after surgery. Or you may have porphyria. This is a very rare blood enzyme deficiency.

Low levels of ADH may mean you have diabetes insipidus or damage to the pituitary gland. Or you may have primary polydipsia. This is extreme thirst because of hypothalamus problems or mental illness.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries small risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

Rarely smoking can make ADH levels higher. Other uncommon causes of higher levels of ADH are pregnancy and taking morphine or certain antidepressants.   

How do I get ready for this test?

Tell your healthcare provider if you smoke, drink alcohol, or take medicines.  Be sure your provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.