Plasma renin activity (PRA)

PRA is sometimes measured, specially in case of certain diseases which present with hypertension or hypotension and in certain tumors.

Unit	Lower limit	Upper limit
ng/(mL*hour)	0.29, 1.9	3.7
μIU/mL	3.3, 21	4

Lower-than-normal levels may indicate:

Disease	Brief Description
ADH therapy	Leads to water retention and thus raised blood pressure.
Salt-retaining steroid therapy	see above
Salt-sensitive essential hypertension	see above
Primary Hyperaldosteronsim	see above and direct inhibition of aldosteron on renin secretion

Higher-than-normal levels may indicate:

Disease	Brief Description
Addison's disease	Kidneys trying to counter low aldosterone output.
Cirrhosis of the liver	Reduced breakdown of Angiotensin.
Essential hypertension	Just more of renin is being secreted by the kidneys.
Hemorrhage (bleeding)	Kidneys trying to raise falling blood pressure.
Hypokalemia	Kidneys trying to raise falling blood pressure due to reduced cardiac output.
Malignant hypertension	Excessive renin is being secreted by the kidneys.
Renin-producing renaltumors	Tumors can secrete substances like this. See tumor markers
Renovascular hypertension	Renal vascular damage leading to reduced JGA perfusion.