Aldosterone Blood Test Explained
An aldosterone blood test measures aldosterone, a hormone from the adrenal glands that helps regulate sodium, potassium, and blood pressure. It is often interpreted together with renin, another hormone in the same regulatory system.
What the test measures
Aldosterone is a steroid hormone made by the adrenal glands, which sit on top of the kidneys. It signals the kidneys to retain sodium and water and release potassium, which in turn influences blood volume and blood pressure. Aldosterone is part of a larger control loop known as the renin-angiotensin-aldosterone system.
Because aldosterone works alongside renin, the two are frequently measured together. The ratio between them helps clinicians tell whether aldosterone is being produced appropriately or independently of the normal signals.
Why a clinician might order it
A clinician may order aldosterone when investigating high blood pressure that is difficult to control, unexplained low potassium, or symptoms that suggest an adrenal hormone imbalance. It is also used to evaluate certain forms of low blood pressure and to assess adrenal function. Aldosterone is often paired with a renin measurement to interpret the result.
How to prepare
Preparation can be detailed. Posture, salt intake, the time of day, and several medications, including some used for blood pressure, can strongly affect aldosterone and renin. The testing team may give specific instructions about timing, position, and which medications to discuss beforehand. Following these instructions carefully improves the reliability of the result.
How results are generally interpreted
Interpretation usually relies on the aldosterone level together with renin.
- High aldosterone with low renin may prompt evaluation for aldosterone produced independently of normal signals.
- High aldosterone with high renin can reflect the system responding to another trigger, such as reduced blood flow to the kidneys.
- Low aldosterone may raise concern about reduced adrenal function and often leads to further testing.
Illustrative reference ranges
The values below are illustrative only and vary by laboratory, posture, salt intake, and time of day. Always use the range and conditions noted on your own report.
| Condition | Illustrative aldosterone (ng/dL) |
|---|---|
| Upright, morning | ~7-30 |
| Lying down | typically lower than upright |
| Interpretation | read together with renin |
Related tests
Aldosterone is usually interpreted with renin and is sometimes evaluated alongside other adrenal hormones such as those covered with the ACTH test. See the blood tests index or explore related conditions for background.
Frequently asked questions
Why is renin measured with aldosterone?
Aldosterone and renin work together in one system, so their ratio helps show whether aldosterone is being produced appropriately or independently.
Can medications affect the result?
Yes. Several medications, including some for blood pressure, can change aldosterone and renin, so the testing team may give specific guidance.
Does body position matter?
It can. Aldosterone often differs between lying down and standing, so the position and timing of the draw are usually specified.
Should I stop my medications before the test?
Never stop a prescribed medication on your own. Ask the clinician who ordered the test how to prepare.
Sources
- MedlinePlus. Endocrine Diseases. https://medlineplus.gov/endocrinediseases.html
- MedlinePlus. Hormones. https://medlineplus.gov/hormones.html
- Endocrine Society. https://www.endocrine.org/