A renin test is often done at the same time as
an aldosterone test. For more information, see the topic
A renin stimulation test may
occasionally be done if blood renin levels are low. To prepare for this test,
you will eat a low-sodium diet for 3 days. A blood renin level will be drawn
and a diuretic, usually furosemide (Lasix), will be put in a vein (intravenous)
in your arm. Normally, blood renin levels will increase, but in Conn's syndrome
blood renin levels will not change after taking the diuretic.
hospitals now measure renin activity with the renin direct immunoassay, which
measures the amount of renin in the blood. A plasma renin activity (PRA) test
measures the production of a hormone called angiotensin I rather than renin itself. A renin
direct immunoassay is easier to do and can generally be done instead of the PRA
test. But in some situations (such as pregnancy), PRA results may be more
accurate than the renin direct immunoassay.