What is a positive ARR?

A widely used Endocrine Society cut-off is an ARR above 30 pmol/L per mU/L, combined with an aldosterone that is meaningfully elevated, typically at least about 270 pmol/L or 10 ng/dL. Both conditions reduce false positives from suppressed renin alone.

What is the difference between PRA and direct renin?

Plasma renin activity (PRA) measures the rate of angiotensin generation in ng/mL/h, while direct renin concentration (DRC) measures renin mass in mU/L. The tool converts PRA to DRC using roughly 8.2 mU/L per ng/mL/h so the ratio uses consistent units.

Why must aldosterone also be elevated?

When renin is strongly suppressed for other reasons, the ratio can rise even with a normal or low aldosterone. Requiring an aldosterone above a minimum threshold alongside a high ratio makes the screen more specific for true primary aldosteronism.

Does a positive screen confirm the diagnosis?

No. A positive ARR is a screening result that should be followed by a confirmatory suppression test such as saline infusion or oral salt loading, then subtype testing. Always interpret against your own laboratory's assay and reference.

Aldosterone-to-Renin Ratio (ARR) Calculator

Q: What can distort the ARR?

Posture, time of sampling, potassium level, and many drugs affect the result. Beta-blockers raise the ratio, while ACE inhibitors, ARBs, diuretics, and mineralocorticoid receptor antagonists lower it. Sampling conditions should be standardised before interpreting the ratio.

The aldosterone-to-renin ratio is the first-line screen for primary aldosteronism, the most common treatable cause of secondary hypertension. This calculator handles the unit conversions that trip people up — aldosterone in pmol/L or ng/dL, renin as activity or concentration — and applies a standard positive-screen rule.

How it works

The ratio is aldosterone divided by renin in consistent units:

aldosterone_pmol = aldosterone_ngdl × 27.7         (if entered in ng/dL)
renin_mU         = PRA_ng_mL_h × 8.2               (if entered as activity)
ARR              = aldosterone_pmol / renin_mU      (pmol/L per mU/L)

A screen is flagged positive when the ARR exceeds 30 pmol/L per mU/L and the aldosterone is at least about 270 pmol/L (10 ng/dL). The aldosterone floor prevents a falsely high ratio when renin alone is suppressed.

Notes and limits

ARR cut-offs are strongly assay- and unit-dependent, so always compare against your own laboratory’s reference. The ratio is sensitive to posture, time of day, potassium, and a long list of antihypertensive drugs: beta-blockers push it up, while ACE inhibitors, ARBs, diuretics, and mineralocorticoid receptor antagonists push it down. A positive screen needs a confirmatory suppression test before any diagnosis. This tool is an educational reference only.