Renin Test
Reviewed
Also called: renin blood test, plasma renin activity (PRA), aldosterone-renin ratio (ARR)
This test measures the level of renin in your blood. Renin is an enzyme made by your kidneys that helps control your blood pressure. It is often done together with an aldosterone test to diagnose adrenal gland disorders, especially primary aldosteronism (PA).
Specimen: blood
Why this test may be ordered
- To find out if your adrenal glands are making too much or too little aldosterone.
- To diagnose primary aldosteronism (PA), a disease caused by having too much aldosterone that causes high blood pressure.
- If you have been diagnosed with high blood pressure, especially if it doesn't respond well to standard blood pressure medicines.
- If you have symptoms of low potassium, such as muscle cramps, muscle weakness, excessive thirst, fatigue, headache, constipation, or racing heartbeat.
Preparation and collection
You may be asked to stop taking certain medicines before your test, so tell your health care provider about everything you take. But don't stop taking any medicines unless your provider tells you to. Some medicines that may affect the results of your test can include: birth control pills, blood pressure medicines, diuretics (water pills). You may also be asked to limit the amount of salt you eat each day before your test. Your provider will explain how to do this and for how long. You should not eat natural black licorice for at least two weeks before your test.
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. This usually takes less than five minutes.
There is very little risk to having a blood test. There may be slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
Your renin test results will usually be compared with your aldosterone test results. The combination helps your provider understand whether your adrenal glands are making too much or too little aldosterone.
- Lower renin / Lower aldosterone: Lower than normal renin / Lower than normal aldosterone. This may mean you have Cushing's syndrome, a disorder in which the adrenal glands make too much of a hormone called cortisol. Limitation: Results should be interpreted by your healthcare provider in the context of your overall health and other test results. Next step: Routine
- Lower renin / Higher aldosterone: Lower than normal renin / Higher than normal aldosterone. This may mean you have primary aldosteronism (PA), a disease caused by having too much aldosterone. PA, also known as primary hyperaldosteronism or Conn syndrome, causes high blood pressure. If not treated, high blood pressure may increase your risk of stroke, heart attack, and kidney failure. Limitation: Results should be interpreted by your healthcare provider in the context of your overall health and other test results. Next step: Prompt
- Higher renin / Lower aldosterone: Higher than normal renin / Lower than normal aldosterone. This may mean you have Addison disease (also called adrenal insufficiency), a condition in which your adrenal glands don't make enough of certain hormones. Limitation: Results should be interpreted by your healthcare provider in the context of your overall health and other test results. Next step: Prompt
- Higher renin / Higher aldosterone: Higher than normal renin / Higher than normal aldosterone. This may mean you have secondary aldosteronism. With this disorder, your adrenal glands are healthy, but another medical condition is causing them to make too much aldosterone. These conditions can include diseases of the heart, liver, and kidneys. Limitation: Results should be interpreted by your healthcare provider in the context of your overall health and other test results. Next step: Prompt
- There is very little risk to having a blood test. There may be slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
- Your position (sitting, standing, etc.), stress level, and certain medicines can affect your renin and aldosterone levels.
- You should not eat natural black licorice for at least two weeks before your test, because it can affect your results.
What to do next
Depending on your results, your provider may recommend medicines and/or diet and lifestyle changes to treat your condition. If you have questions about your results, talk to your provider.
- What do my renin and aldosterone levels indicate about my adrenal gland function?
- Do I need any follow-up tests or imaging?
- Should I adjust my blood pressure medications based on these results?