Renin
Renin is an enzyme produced by the kidneys that helps control blood pressure. Renin works by activating other chemicals to narrow (constrict) blood vessels, which increases blood pressure; a decrease in renin levels helps lower blood pressure.
Normally, this mechanism keeps blood pressure within a healthy range. But some people develop chronic high blood pressure (hypertension). When this occurs, medicines may be used that block the action of renin on blood vessels.
Why is a renin blood test 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 is a renin blood test 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 do you prepare for a renin blood test?
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.
What do the results of a renin blood test mean?
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.
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