Renin blood test
The renin test measures the level of renin in blood.
Plasma renin activity; Random plasma renin; PRA
How the Test is Performed
A blood sample is needed.
How to prepare for the test
Certain medicines may affect the results of this test. Your doctor will tell you if you need to stop taking any medicines. Do not stop any medicine before talking to your doctor.
Medicines that can affect renin measurements include:
- Birth control pills
- Blood pressure drugs
- Medicines that enlarge blood vessels (vasodilators); these are usually used to treat high blood pressure or heart failure
- Water pills (diuretics)
Eat a normal, balanced diet with moderate sodium content (no more than 3 grams a day) for 3 days before the test.
Be aware that renin level can be affected by pregnancy as well as time of day and 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. These soon go 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 see if you are sensitive to salt.
Test results can help guide your doctor in choosing the correct medicine. Salt-sensitive patients with high blood pressure associated with low renin levels respond well to diuretic medicines.
Normal values range from 0.2 to 3.3 ng/mL/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
High levels of renin may be due to:
Low renin levels may be due to:
- Adrenal glands releasing too much aldosterone hormone (hyperaldosteronism)
- High blood pressure that is salt-sensitive
- Treatment with antidiuretic hormone
- Treatment with steroid medicines that causes the body to retain salt
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)
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Gruber HA, Farag AF. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 24.
Oh MS. Evaluation of renal function, water electrolytes, and acid-base balance. In: McPherson RA, Pincus MR, eds. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 14.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.