What this test measures
Aldosterone is the principal mineralocorticoid produced by the zona glomerulosa of the adrenal cortex. It tells the kidneys to retain sodium (and therefore water) and excrete potassium. Aldosterone output is normally driven by the renin-angiotensin system in response to low blood pressure or low sodium.
The test measures aldosterone concentration in serum, almost always paired with plasma renin to compute the aldosterone-to-renin ratio (ARR) — the standard screening tool for primary aldosteronism.
Why it matters
Primary aldosteronism (Conn's syndrome) is the most common surgically curable cause of secondary hypertension and is far more common than older textbooks suggest — large international screening studies put the prevalence at 5–10% of unselected hypertensive patients and up to 20% in resistant hypertension. Given the burden of hypertension in India (an estimated 200+ million adults), the diagnostic yield is significant.
Flagging this matters because the treatment is specific: an adrenal adenoma can be removed surgically, and bilateral hyperplasia responds well to mineralocorticoid-receptor blockers (spironolactone, eplerenone). Untreated primary aldosteronism causes more cardiovascular damage than blood-pressure-matched essential hypertension.
How to prepare
Sample is collected in the morning (8–10 am) after the patient has been upright for 2 hours. Sodium intake should be unrestricted (≥ 6 g salt/day) for at least 3 days before testing — sodium restriction raises aldosterone artificially. Stop spironolactone, eplerenone and high-dose diuretics for 4–6 weeks before testing if clinically possible. Discuss with your doctor about ACE-inhibitors, ARBs, beta-blockers and direct renin inhibitors — they can all distort the ARR, though many guidelines now allow most to be continued with careful interpretation.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Aldosterone (ng/dL)[1][2] | < 21 ng/dL upright (morning, normal sodium intake) | Low aldosterone with high renin suggests primary adrenal insufficiency (Addison's) or isolated hypoaldosteronism. Low aldosterone with low renin in a hypertensive patient may indicate Liddle syndrome, apparent mineralocorticoid excess, or congenital adrenal hyperplasia. | High aldosterone with suppressed renin (ARR > 20–30) in a hypertensive patient = primary aldosteronism — needs confirmation with a saline infusion / oral salt-loading test and then CT adrenals + adrenal vein sampling to distinguish adenoma from hyperplasia. High aldosterone with high renin = secondary (renovascular disease, heart failure, cirrhosis, diuretic use). |
Aldosterone + Renin — paired interpretation
| Aldosterone | Renin | ARR (ng/dL ÷ ng/mL/hr) | Likely cause |
|---|---|---|---|
| High | Suppressed | > 20–30 | Primary aldosteronism — confirm and image adrenals |
| High | High | Normal/low | Secondary aldosteronism (renal artery stenosis, heart failure, cirrhosis, diuretic use) |
| Low | High | Low | Primary adrenal insufficiency (Addison's) |
| Low | Low | Low | Liddle syndrome, apparent mineralocorticoid excess, exogenous mineralocorticoid |
| Normal | Normal | Normal | Essential hypertension |
Frequently asked questions
Why am I being tested for aldosterone if I just have high blood pressure?
Roughly 1 in 10 patients with hypertension and 1 in 5 with resistant hypertension have primary aldosteronism — a treatable cause that current Indian and international guidelines recommend screening for, especially if blood pressure is hard to control, the patient is young, or potassium runs low.
Do I need to stop my BP medicines before the test?
Spironolactone and eplerenone must be stopped 4–6 weeks before. Many other antihypertensives (ACE-inhibitors, ARBs, beta-blockers) can affect the result, but recent guidelines accept testing on them with careful interpretation. Never stop blood pressure medication on your own — your doctor will plan the switch.
Why do I have to eat salt before the test?
Aldosterone goes up when you eat less salt. To get a meaningful baseline, your sodium intake needs to be in a normal-to-liberal range (about 6 g of salt or more per day) for at least 3 days. Avoid extreme low-salt diets that week.
What is the aldosterone-to-renin ratio (ARR)?
A simple division — serum aldosterone (ng/dL) divided by plasma renin (ng/mL/hr). An ARR above 20–30 is the standard screen for primary aldosteronism. The ratio matters more than either value alone.
My potassium is low and BP is high — could this be it?
Yes — that combination (hypokalemic hypertension) is a classic presentation of primary aldosteronism, though potassium can also be normal. It is one of the strongest clinical clues.
Is primary aldosteronism curable?
A unilateral adrenal adenoma (Conn's tumour) can be removed laparoscopically — BP often improves dramatically. Bilateral hyperplasia is managed with mineralocorticoid-receptor blockers, which also work very well.
Why do I have to be upright for 2 hours before the draw?
Standing changes plasma renin and aldosterone — overnight recumbent samples and upright samples are different reference ranges. The "morning, seated for 5–15 min after 2 h upright" protocol is the international standard.
Related Hormones / Endocrine tests
Tests commonly ordered alongside ALDOSTERONE, or that help interpret an unexpected result.
Sources & references
- Endocrine Society — Primary Aldosteronism Guideline · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — Aldosterone Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Aldosterone · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Laboratories — Aldosterone, Serum · accessed 2026-05-30T00:00:00.000Z
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