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 is present, an 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 (3 grams 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 1gal. 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.