Renin (Direct / Plasma Renin)

Hormones marker

Renin

Renin (Direct / Plasma Renin)

Category: Hormones
Unit: mIU/L

Enzyme released by the juxtaglomerular cells of the kidney that initiates the renin-angiotensin-aldosterone system (RAAS). Reported either as direct renin concentration (mIU/L) or as plasma renin activity (ng/mL/h).

PED Notes

A key partner test to aldosterone when investigating hypertension in enhanced athletes. Suppressed renin together with high aldosterone (a raised aldosterone-renin ratio) signals primary aldosteronism, a treatable cause of resistant high blood pressure. Renin is heavily influenced by drugs many athletes use: beta-blockers and NSAIDs lower it, while ACE inhibitors, angiotensin receptor blockers, and diuretics raise it. Posture, salt intake, time of day, and potassium all shift the result, so collection must be standardised.

When high

When HIGH:

  • High renin reflects RAAS activation: dehydration, sodium restriction, diuretic use, renal artery narrowing, or heart failure
  • High renin with high aldosterone in step is secondary hyperaldosteronism; investigate and treat the underlying cause
  • Many antihypertensive drugs (ACE inhibitors, ARBs, diuretics) raise renin and can confound interpretation

Practical notes:

  • Standardise posture, timing, salt intake, and potassium before testing
  • A high renin with low aldosterone can point to mineralocorticoid deficiency or adrenal insufficiency; pair with aldosterone, electrolytes, and cortisol

When low

When LOW:

  • Suppressed renin with elevated aldosterone and a raised aldosterone-renin ratio is the screen for primary aldosteronism; pursue confirmatory testing under endocrinology
  • Suppressed renin can also follow licorice ingestion, high sodium intake, or beta-blocker and NSAID use
  • Low renin in an AAS user with hypertension and low-normal potassium should prompt an ARR rather than reassurance

Clinical context:

  • Two assay formats exist and are NOT interchangeable: direct renin concentration (DRC, reported in mIU/L) and plasma renin activity (PRA, reported in ng/mL/h). Roughly, 1 ng/mL/h of PRA corresponds to about 7-8 mIU/L of DRC, but always use your lab's units and reference range
  • The aldosterone-renin ratio threshold depends entirely on which renin assay and which units are used
  • Standardise collection conditions and, with a clinician, review interfering medications before screening

History Chart

Reading History

Frequently Asked Questions

Reference Ranges

Standard Range

4.4 - 46 mIU/L

VitalMetrics Range

4.4 - 46 mIU/L

Statistics