Many things can affect renin test results. Your doctor will talk with you about any abnormal results that may be related to your symptoms and past health.
A high renin value can mean kidney disease, blockage of an artery leading to a kidney, Addison's disease, cirrhosis, excessive bleeding (hemorrhage), or malignant high blood pressure is present.
A low renin value can mean some types of kidney disease or Conn's syndrome is present.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- Eating natural black licorice in the 2 weeks before the test.
- Taking some medicines used to treat high blood pressure.
- Taking aspirin, caffeine, estrogens, or diuretics.
- Your position (standing, sitting, or lying down) before the test is done or the time of day when the blood sample is drawn, as well as recent salt intake.
- Taking very high doses of corticosteroids.
- Being pregnant.
What To Think About
- A renin test is often done at the same time as an aldosterone test. To learn more, see the topic Aldosterone.
- 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.
- Many 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.
- Other tests that may be done to investigate high blood pressure include duplex Doppler ultrasound, arteriography, magnetic resonance imaging (MRI), and magnetic resonance angiography (MRA).