This test measures the level of renin in the blood. Renin is a hormone made by the kidneys. It controls the production of another hormone called aldosterone, which is made in the adrenal glands. These are two small glands located above the kidneys. Aldosterone helps manage blood pressure and maintain healthy levels of potassium and sodium in the body.
If renin and/or aldosterone levels are not normal, it can be a sign of a serious adrenal gland disorder. Because the two hormones work together, an aldosterone test is often done at the same time as a renin test.
Other names: renin blood test, plasma renin activity (PRA) aldosterone-renin ratio (ARR)
What is it used for?
A renin test (or renin and aldosterone test) is used to find out if the adrenal glands are making too much or too little aldosterone.
The test is especially useful in diagnosing primary aldosteronism (PA), a disease that happens from having too much aldosterone. PA, also known as primary hyperaldosteronism or Conn syndrome, causes high blood pressure. If not treated, high blood pressure increases the risk of stroke, heart attack, and kidney failure.
Why do I need a renin test?
You may need a renin test if you’ve been diagnosed with high blood pressure, especially if it doesn’t respond well to standard blood pressure medicines. The test can show whether PA is causing the condition.
Sometimes PA causes low potassium levels, so you may also need this test if you have symptoms of low potassium. These include:
What happens during a renin 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. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Will I need to do anything to prepare for this test?
You may be asked to stop taking certain medicines two to four weeks before your test. These include:
- Birth control pills
- Blood pressure medicines
- Diuretics (water pills)
You may also be asked to follow a low-salt diet for three days before your test.
Are there any risks to this test?
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.
What do the results mean?
If your results show a higher than normal amount of renin, it may mean you have:
- Addison disease, a condition in which your adrenal glands don’t make enough of certain hormones
- Cirrhosis, scarring of the liver
- Dehydration
If your results show a lower than normal amount of renin, it may mean you have:
- Primary aldosteronism (PA)
- Kidney disease
Most often, your renin test results will be compared with aldosterone test results. These results may show one of the following:
- 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.
- Lower than normal renin/Higher than normal aldosterone. This may mean you have PA.
- Higher than normal renin/Lower than normal aldosterone. This may mean you have Addison disease.
- Higher than normal renin/Higher than normal aldosterone. This may mean you have secondary aldosteronism. In this disorder, a medical condition in another part of the body causes the adrenal glands to make too much aldosterone. These conditions include diseases of the heart, liver, and kidneys.
Depending on your results, your provider may recommend medicine and/or diet and lifestyle changes to treat your condition.
If you have questions about your results, talk to your health care provider.
Is there anything else I need to know about a renin test?
Licorice can affect your test results, so you should not eat licorice for at least two weeks before your test. But only real licorice, which comes from licorice plants, has this effect. Most licorice products sold in the U.S. don’t contain any real licorice. Check the package ingredient label to be sure.
Courtesy of MedlinePlus from the National Library of Medicine.