Vasopressin, arginine vasopressin, AVP
This test measures the amount of antidiuretic hormone (ADH) in your blood.
ADH is made by your hypothalamus. ADH regulates your body's balance of water. Certain conditions can affect the amount of ADH that your body produces. These include hyponatremia, or low sodium levels in your bodily fluids, and a condition called diabetes insipidus, which is marked by frequent urination and extreme thirst.
You may have this test if your doctor suspects that you have a disorder that affects your ADH levels.
Your doctor may also order other tests, including a water deprivation test. In this test, you stop drinking fluids for several hours, and then your urine and blood are measured for concentrations of solid particles.
Your doctor may also order a water loading test. In this test, you drink specific amounts of water, and then your doctor measures the water levels in your urine over time.
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
Results are given in picograms per microliter (pg/uL). Normal ADH levels vary from 0.5 to 2 pg/uL.
Higher than normal results may mean that you have lung tumors, central nervous system tumors, a fluid imbalance after surgery, or even porphyria, a very rare blood enzyme deficiency.
Low levels of ADH may mean you have diabetes insipidus, damage to the pituitary gland, or primary polydipsia, which is extreme thirst because of hypothalamus problems or mental illness.
The test requires a blood sample, which is drawn through a needle from a vein in your arm.
Taking a blood sample with a needle carries 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.
Rarely, smoking can increase ADH levels. Other uncommon causes of higher levels of ADH are pregnancy and taking morphine or certain antidepressants.
Tell your doctor if you smoke, drink alcohol, or take medications. Be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.