Plasma renin activity; Random plasma renin; PRA
The renin test measures the level of renin in blood.
How to Prepare for the Test
Certain medicines may affect the results of this test. Your health care provider will tell you if you need to stop taking any medicines. DO NOT stop any medicine before talking to your provider.
Medicines that can affect renin measurements include:
- Birth control pills
- Blood pressure drugs
- Medicines that dilate blood vessels (vasodilators). These are usually used to treat high blood pressure or heart failure.
- Water pills (diuretics)
Your provider may instruct you to limit your sodium intake before the test.
Be aware that renin level can be affected by pregnancy, as well as the time of day and the body position when blood is drawn.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
Renin is a protein (enzyme) released by special kidney cells when you have a decreased salt (sodium) level or low blood volume.
If you have high blood pressure, your doctor may order a renin and aldosterone test to help determine the cause of your elevated blood pressure. Test results can help guide your doctor in choosing the correct treatment.
For normal sodium diet, normal value range is 0.6 to 4.3 ng/mL/hour (0.6 to 4.3 µg/L/hour). For low sodium diet, normal value range is 2.9 to 24 ng/mL/hour (2.9 to 24 µg/L/hour).
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
A high level of renin may be due to:
A low level of renin may be due to:
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Bailey MA, Shirley DG, Unwin RJ. Renal physiology. In: Johnson RJ, Feehally J, Floege J, eds. Comprehensive Clinical Nephrology. 5th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 2.
Chernecky CC, Berger BJ. Renin activity (plasma renin activity, PRA) - plasma. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:972-974.