Aldosterone in Blood

An aldosterone test measures the level of aldosterone (a hormone made by the adrenal glands), in the blood. 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:

1. Measure the amount of aldosterone released into the body by the adrenal glands.
2. Check for a tumor in the adrenal glands.
3. Find the cause of high blood pressure or low blood potassium levels. This is done when overactive adrenal glands or an abnormal adrenal growth are suspected.

How To Prepare

An aldosterone test is often done at the time of a routine blood test. You do not need to do anything before having routine blood tests.

If you are having follow-up aldosterone blood tests, your doctor may give you the following instructions:

* Eat foods with a normal amount of sodium (3 grams per day) for 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.
* Do not eat natural black licorice for 2 weeks before this 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 2 weeks before the test. These include hormones (such as progesterone and estrogens), corticosteroids, diuretics, and many medicines used to treat high blood pressure, especially spironolactone (Aldactone).

The amount of aldosterone in blood changes depending on whether you are standing up or lying down. If initial results show a problem, repeat tests may be done in different positions and under different conditions, such as not eating before the test or eating foods that contain a specific amount of salt. Your doctor may ask you to have your blood drawn at a certain time because aldosterone levels are highest in the early morning.