A renin assay blood test is done to find the
high blood pressure (hypertension). Renin is an
enzyme made by special cells in the
kidneys . Renin works with aldosterone (a
hormone made by the
adrenal glands) and several other substances to help
balance sodium and
potassium levels in the blood and fluid levels in the
body, which affects your blood pressure.
A renin test is often
done at the same time as an aldosterone test. In some people, it may be normal
to have high blood levels of both renin and aldosterone. If renin levels are
low and aldosterone levels are high, a tumor may be present in the
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
estrogens, and high blood pressure medicines
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
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.
professional drawing blood will:
- Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
- Clean the needle site with
- Put the needle into the vein. More than one needle stick
may be needed.
- Attach a tube to the needle to fill it with
- Remove the band from your arm when enough blood is
- Put a gauze pad or cotton ball over the needle site as
the needle is removed.
- Put pressure on the site and then put on a
How It Feels
The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or