An aldosterone test measures the level of aldosterone (a hormone made by the adrenal glands), in the urine. Aldosterone helps regulate sodium and potassium levels in the body. This helps control blood pressure and the balance of fluids and electrolytes in the blood.
The kidney hormone renin normally stimulates the adrenal glands to release aldosterone. High levels of both renin and aldosterone are normally present when the body is trying to conserve fluid and salt (sodium). When a tumor that makes aldosterone is present, your aldosterone level will be high while a renin level will be low. Usually a renin activity test is done when the aldosterone level is measured.
Why It Is Done
An aldosterone test is done to:
- Measure the amount of aldosterone released into the body by the adrenal glands.
- Check for a tumor in the adrenal glands.
- Find the cause of high blood pressure or low potassium levels. This is done when overactive adrenal glands or an abnormal adrenal growth are suspected.
How To Prepare
Eat foods with a normal amount of sodium (2,300 mg per day) for at least 2 weeks before the test. Do not eat foods that are very salty, such as bacon, canned soups and vegetables, olives, bouillon, soy sauce, and salty snacks like potato chips or pretzels. A low-salt diet can also increase aldosterone levels. Tell your doctor if you are on a low-salt food plan.
Do not eat natural black licorice for at least 2 weeks before an aldosterone test.
Many medicines may change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take. You may be asked to stop taking some medicines for about 2 weeks before the test. These include hormones (such as progesterone and estrogen), corticosteroids, diuretics, and many medicines used to treat high blood pressure, especially spironolactone (Aldactone) and eplerenone (Inspra).
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).
How It Is Done
- You start collecting your urine in the morning. When you first get up, empty your bladder but do not save this urine. Write down the time that you urinated to mark the beginning of your 24-hour collection period.
- For the next 24 hours, collect all your urine. Your doctor or lab will usually provide you with a large container that holds about 1 gal (4 L). The container has a small amount of preservative in it. Urinate into a small, clean container, and then pour the urine into the large container. Do not touch the inside of the container with your fingers.
- Keep the large container in the refrigerator for the 24 hours.
- Empty your bladder for the final time at or just before the end of the 24-hour period. Add this urine to the large container and record the time.
- Do not get toilet paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in the urine sample.
How It Feels
There is no pain while collecting a 24-hour urine sample.
There is no chance for problems while collecting a 24-hour urine sample.
The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
High aldosterone levels can be caused by:
- A tumor in the adrenal glands (Conn's syndrome).
- Heart failure.
- Kidney disease.
- Liver disease.
- A condition during pregnancy that causes high blood pressure (preeclampsia).
- Some medicines that are used treat high blood pressure.
Low aldosterone levels can be caused by:
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- Eating large amounts of natural black licorice.
- Pregnancy. Aldosterone levels may be high in the third trimester of pregnancy.
- Taking medicines, such as female hormones (progesterone and estrogen), corticosteroids, heparin, opiates, laxatives, nonsteroidal anti-inflammatory drugs (NSAIDs), or diuretics. Most medicines used to treat high blood pressure, especially spironolactone (Aldactone), eplerenone (Inspra), and beta-blockers, increase blood levels of aldosterone and renin.
- Exercising hard or being under emotional stress.
- Your age. Aldosterone levels normally decrease with age.
What To Think About
- The kidney hormone renin normally controls how much aldosterone is released by the adrenal glands. Usually a renin activity test is done when the aldosterone level is measured. To learn more, see the topic Renin.
- Aldosterone is more commonly measured in a blood test. To learn more, see the topic Aldosterone in Blood.
- If you have overactive adrenal glands or an abnormal adrenal growth, potassium levels may also be tested. To learn more, see the topic Potassium (K) in Blood.
Other Works Consulted
American Association of Clinical Endocrinologists (2006). Medical guidelines for clinical practice for the diagnosis and treatment of hypertension. Endocrine Practice, 12(2): 195-222.
Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Adam Husney, MD - Family Medicine
Specialist Medical ReviewerAlan C. Dalkin, MD - Endocrinology
Current as ofNovember 20, 2015