Renin
Kidney enzyme and hormone that helps control blood pressure via aldosterone
Also known as
Definition
Renin is an enzyme the kidneys release when blood pressure or sodium drops or potassium rises. It also acts like a hormone: it controls the production of aldosterone in the adrenal glands, which keeps blood pressure stable by balancing sodium and potassium. When renin rises, aldosterone usually rises too. Both are highest in the morning and change throughout the day. That is why renin is almost always measured together with aldosterone, often as the aldosterone-to-renin ratio.
| Parameter | Value |
|---|---|
| Unit | ng/ml/h (plasma renin activity) |
| Reference Range | For plasma renin activity on a normal-sodium diet, MedlinePlus lists 0.2–1.6 ng/ml/h lying down and 0.5–4.0 ng/ml/h standing. Labs use different methods and ranges; the range printed on your report is what counts. Your doctor interprets the result, usually together with aldosterone. |
Agree on your personal target range with your doctor.
1 ng/ml/h equals 1 µg/l/h (same number). If your lab measures renin concentration instead of activity, different units and ranges apply that cannot be compared directly.
↓ What a low value means
Low renin can be related to primary aldosteronism (Conn syndrome), in which the adrenal glands make too much aldosterone. Other possible links are kidney disease, for example due to diabetes, salt-sensitive high blood pressure, a very high-salt diet, and medicines such as salt-retaining steroids or antidiuretic hormone. Low renin together with low aldosterone can point to Cushing syndrome. Discuss any deviation with your doctor.
↑ What a high value means
Elevated values can be related to Addison disease (adrenal insufficiency), liver cirrhosis, dehydration, bleeding or heart failure. High blood pressure caused by narrowed kidney arteries, nephrotic syndrome, rare renin-producing kidney tumors, a very low-salt diet or sudden, very high blood pressure can also raise renin. When renin and aldosterone are both high, this is called secondary aldosteronism. Discuss any deviation with your doctor.
When to test
Renin is usually measured in high blood pressure, especially when it responds poorly to standard medicines, or with signs of low potassium. Birth control pills, blood pressure medicines, vasodilators, diuretics, pregnancy, time of day, body position, stress and salt intake affect the value. According to MedlinePlus, avoid natural licorice for at least two weeks beforehand. Only stop medicines after talking to your doctor.
Frequently asked questions
Why is renin measured together with aldosterone? +
Renin controls aldosterone production, and both values normally move in the same direction. Only the combination shows whether the adrenal glands make too much aldosterone on their own or are responding to a signal from the kidneys. That is why the aldosterone-to-renin ratio is often measured.
What do the combinations of renin and aldosterone mean? +
According to MedlinePlus, low renin with high aldosterone can fit primary aldosteronism, high renin with low aldosterone Addison disease, both high secondary aldosteronism, and both low Cushing syndrome. The assessment belongs with your doctor.
Does body position during the blood draw matter? +
Yes. Renin is higher standing than lying down and varies with the time of day. The practice may therefore specify a particular time or body position for the blood draw.
Do I need to stop medicines before the test? +
Not on your own. Some medicines change the renin value, so your doctor may order a pause. Tell the practice what you take and do not stop anything without talking to them first.
Renin
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.