Renin Blood Test

Why It Is Done

A renin test is done to find the cause of high blood pressure (hypertension), especially when potassium levels in the blood are low.

How To Prepare

For 2 to 4 weeks before the test, you may be asked to stop taking medicines that can affect the test, such as diuretics, estrogens, and high blood pressure medicines (especially beta-blockers and ACE inhibitors). Your doctor may have you take other medicines for a few weeks that will not change the renin test results.

Do not eat natural black licorice for 2 weeks before the test. Do not eat or drink foods that contain caffeine the day before the test. Natural licorice and caffeine can change the test results.

For 3 days before a renin test, you may be asked to follow a special low-sodium diet.

You may be asked to not eat or drink anything for 8 hours before the test.

How It Is Done

You may need to sit or lie down to relax for 1 to 2 hours before your blood is collected. A second blood sample may be collected after you move around for 2 hours.

A health professional uses a needle to take a blood sample, usually from the arm.

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

Normal

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

High values

A high renin value can mean that kidney disease, blockage of an artery leading to a kidney, Addison's disease, cirrhosis, excessive bleeding (hemorrhage), or a hypertensive emergency is present.

Low values

A low renin value can mean that some types of kidney disease or Conn's syndrome is present.