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, a protein that speeds up certain chemical reactions in your body.
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. You should not eat natural black licorice for at least two weeks before your test, because it can affect your results.
A health care professional will take a blood sample from a vein in your arm, using a small needle. 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
Most often, your renin test results will be compared with your aldosterone test results.
- Lower renin / lower 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: Your position (sitting, standing, etc.), stress level, and certain medicines can affect your renin and aldosterone levels. Next step: Depending on your results, your provider may recommend medicines and/or diet and lifestyle changes to treat your condition.
- Lower renin / higher aldosterone: Lower than normal renin/Higher than normal aldosterone. This may mean you have PA. Limitation: These levels are highest in the morning and change throughout your day. Next step: Depending on your results, your provider may recommend medicines and/or diet and lifestyle changes to treat your condition.
- Higher renin / lower aldosterone: Higher than normal renin/Lower than normal aldosterone. This may mean you have Addison disease. Limitation: Your position (sitting, standing, etc.), stress level, and certain medicines can affect your renin and aldosterone levels. Next step: Depending on your results, your provider may recommend medicines and/or diet and lifestyle changes to treat your condition.
- Higher renin / higher 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. Limitation: These conditions can include diseases of the heart, liver, and kidneys. Next step: If you have questions about your results, talk to your provider.
- 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?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.