At a Glance
Why Get Tested?
To determine if your aldosterone or renin levels are abnormal; to detect hyperaldosteronism (overproduction of aldosterone) or hypoaldosteronism (underproduction of aldosterone)
When to Get Tested?
If your doctor identifies an electrolyte imbalance or you develop symptoms of hyperaldosteronism, such as elevated blood pressure or muscle weakness
A blood sample drawn from a vein in your arm or a 24-hour urine sample
The Test Sample
What is being tested?
Aldosterone is a hormone that regulates the retention of sodium (salt) and water by the kidney and also regulates the excretion of potassium. It plays an important role in the control of blood pressure.
Aldosterone is produced by the adrenal glands, located at the top of each kidney. Its production is stimulated by a complex process that includes several other ‘hormones’, the most important of these being renin and angiotensin II. Renin, produced by the kidney, stimulates production of angiotensin II in the bloodstream. Angiotensin II then regulates production of aldosterone. Normally when renin increases, aldosterone increases; when renin is low, aldosterone decreases. Renin is released from the kidney when there is a drop in blood pressure, a decrease in sodium concentration, or an increase in potassium concentration.
Both aldosterone and renin are highest in the morning and vary throughout the day. They are affected by a person’s position, by stress and by a variety of prescribed medications.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm for measuring a plasma aldosterone and/or renin level. Because the levels of aldosterone and renin change when a person goes from lying down to standing up, your doctor may collect one sample whilst you are lying down and another after you have been upright for a few hours. A 24-hour urine collection for aldosterone is preferred by some physicians, since plasma aldosterone levels vary by the time of day the samples are collected. Renin is always measured in the blood.
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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.