At a Glance
Why Get Tested?
To help detect, diagnose, and determine the cause of antidiuretic hormone (ADH) deficiency or excess; to investigate low blood sodium levels (hyponatremia); to distinguish between the two types of diabetes insipidus
When to Get Tested?
When you have hyponatremia or have persistent thirst, frequent urination, and dehydration
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None needed for an ADH test; however, talk to your doctor about required preparation when the ADH test is performed as part of a water deprivation ADH stimulation test or a water loading ADH suppression test.
The Test Sample
What is being tested?
The ADH test measures the amount of antidiuretic hormone (ADH) in the blood. ADH, also called arginine vasopressin (AVP), is a hormone produced by the hypothalamus and stored in the posterior pituitary gland. Antidiuretic hormone helps regulate water balance in the body by controlling the amount of water the kidneys reabsorb.
ADH is normally released by the pituitary in response to sensors that detect increases in blood osmolality or decreases in blood volume. The kidneys react to ADH by conserving water and producing urine that is more concentrated. The retained water dilutes the blood, lowers its osmolality, and increases blood volume and pressure. If this is not sufficient to restore the water balance, then thirst is also stimulated so that the affected person will drink more water.
There are a variety of disorders, conditions, and medications that can affect either the amount of ADH released or the kidneys' sensitivity to it. ADH deficiency and excess can cause acute and chronic symptoms that, in rare cases, may become life-threatening. If there is too little ADH or the kidneys do not respond to ADH, then too much water is lost through the kidneys, the urine produced is more dilute than normal, and the blood becomes more concentrated. This can cause excessive thirst, frequent urination, dehydration, and high blood sodium (hypernatremia). If there is too much ADH, then water is retained, blood volume increases, and the person may experience nausea, headaches, disorientation, lethargy, and hyponatremia.
The ADH test is not widely used to diagnose these conditions. Often, a diagnosis is made on the basis of clinical history and other laboratory tests such as urine and blood osmolality and electrolytes.
ADH deficiency is called diabetes insipidus. There are two types of this disorder: central and nephrogenic. Central diabetes insipidus is associated with a lack of ADH production by the hypothalamus or release from the pituitary and may be due to a variety of causes, including an inherited genetic defect, head trauma, a brain tumor, or due to an infection that causes encephalitis or meningitis. Nephrogenic diabetes insipidus originates in the kidney and is associated with a lack of response to ADH, causing an inability to concentrate urine. It may be inherited or caused by a variety of kidney diseases. Both types of diabetes insipidus lead to the excretion of large quantities of dilute urine.
Increased levels of ADH are often seen with "syndromes of inappropriate antidiurectic hormone" (SIADH). SIADH is characterized by production of too much ADH, resulting in water retention, hyponatremia, and decreased blood osmolality. It may be due to a wide number of diseases and conditions that either stimulate excessive ADH production and release or that prevent its suppression. SIADH may also be seen with cancers that produce ADH or ADH-like substances independent of the hypothalamus and pituitary glands. Regardless of the cause or source, excessive ADH causes low blood sodium and osmolality because water is retained and blood volume is increased.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed for an ADH test. However, talk to your doctor about required preparation when the ADH test is performed as part of a water deprivation ADH stimulation test or a water loading ADH suppression test.
The Test
How is it used?
The antidiuretic hormone (ADH) test is ordered by itself or along with or following other tests to help detect, diagnose, and determine the cause of antidiuretic hormone deficiencies and excesses. However, this test is not widely used; diagnoses of these conditions are often based on clinical history and other laboratory tests, such as blood and urine osmolality as well as electrolytes.
Symptoms of ADH deficiency are often seen with one of two types of diabetes insipidus. Central diabetes insipidus is a decrease in the production of ADH by the hypothalamus or in the release of ADH from the pituitary; nephrogenic diabetes insipidus is characterized by a decrease in the kidney's response to ADH. A water deprivation ADH stimulation test is sometimes used to distinguish between these types. It involves fluid restriction, an ADH test, and the administration of ADH (vasopressin). Several blood and urine osmolality measurements are performed at timed intervals before and after vasopressin is given in order to monitor the body's response to the drug. This procedure must be performed under close medical supervision as it can sometimes lead to severe dehydration and can pose a risk to some people with underlying diseases.
Symptoms of increased levels of ADH are often seen with "Syndromes of Inappropriate ADH production" or SIADH. Testing for SIADH may include blood and urine osmolality, sodium, potassium, and chloride tests as well as an ADH measurement. A water loading ADH suppression test is sometimes performed. With this procedure, a fasting person is given specific quantities of water and then the amount of urine produced and the changes in urine and blood osmolality are monitored over time. An ADH test is also performed. This procedure must also be performed under medical supervision as it can be risky in those with kidney disease and can sometimes result in severe hyponatremia.
Other testing may be performed to help distinguish SIADH from other disorders that can cause edema, hyponatremia, and/or decreased urine production, such as congestive heart failure, liver disease, kidney disease, and thyroid disease.
When is it ordered?
An ADH test may be ordered by itself, along with other tests, or as part of a water deprivation or water loading procedure whenever excess or deficient ADH production and secretion is suspected. It may be ordered when a person has hyponatremia without an identifiable cause and/or has symptoms associated with SIADH. If SIADH develops gradually, there may be no symptoms, but if the condition is acute, the signs and symptoms are usually those associated with water intoxication and may include:
- Headache
- Nausea, vomiting
- Confusion
- In severe cases, coma and convulsions
An ADH test may be ordered when a person has excessive thirst and frequent urination and the doctor suspects diabetes insipidus.
What does the test result mean?
ADH test results alone are not diagnostic of a specific condition. The results are usually evaluated in conjunction with a person's medical history, physical examination, and results of other tests. Excesses and deficiencies of ADH may be temporary or persistent, acute or chronic, and may be due to an underlying disease, an infection, an inherited condition, due to a surgery or trauma, or even due to a psychological problem that leads to excess water drinking.
Increased ADH levels are often associated with SIADH and may be seen with a variety of cancers, including leukemia, lymphoma, lung cancer, pancreatic, bladder, and brain cancer. Greatly increased concentrations of ADH may be seen with systemic cancers that produce ADH. Moderate increases in ADH may be seen with nervous system disorders such as Guillain-Barré syndrome, multiple sclerosis, epilepsy, acute intermittent porphyria, with pulmonary disorders such as cystic fibrosis, emphysema, and tuberculosis, and in those with HIV/AIDS. The ADH test may sometimes be ordered to help investigate hyponatremia and its associated symptoms, and to identify SIADH, but it is not generally ordered to diagnose or monitor any of the diseases or conditions that may cause it.
A low ADH may be seen with central diabetes insipidus, compulsive water drinking, and with low serum osmolality. An increased ADH may be seen with nephrogenic diabetes insipidus, with dehydration, trauma, and surgery.
With ADH suppression or stimulation tests, a doctor is looking for appropriate levels of ADH, osmolality, and kidney water retention responses.
- A water loading ADH suppression test may be used to help diagnose SIADH. With this test, those with SIADH typically have a decreased blood sodium and osmolality, but a normal urine sodium. They do not produce as much urine as expected, urine osmolality is high relative to serum osmolality, and the ADH concentration is in excess of what would be appropriate.
- A water deprivation ADH stimulation test may be used to differentiate between the two types of diabetes insipidus.
- Central diabetes insipidus is characterized by abnormally low production of ADH and the inability to concentrate urine that is reflected as an increase in urine osmolality after ADH administration but not an increase due to water deprivation alone.
- Nephrogenic diabetes insipidus is the kidney's inability to respond to ADH that is reflected as no change in urine osmolality before or after ADH administration.
Is there anything else I should know?
In general, the ability to concentrate urine decreases with age.
ADH secretion increases when a person is standing, at night, and with pain, stress and exercise. Secretion decreases with hypertension and when someone is lying down.
Many drugs can affect ADH levels. They include:
- Drugs that stimulate ADH release, such as: barbiturates, desipramine, histamine, morphine, nicotine, amitriptyline and carbamazepine.
- Drugs that promote ADH action, such as: acetaminophen, metformin, tolbutamide, aspirin, theophylline, and non-steroidal anti-inflammatory drugs.
- Drugs that decrease ADH or its effects, such as: ethanol, lithium, and phenytoin.
Common Questions
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Article Sources
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
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