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
There is very little chance of a problem from
having a blood sample taken from a vein.
You may get a small bruise at the site. You
can lower the chance of bruising by keeping pressure on the site for several
In rare cases, the vein may become swollen after the
blood sample is taken. This problem is called phlebitis. A warm compress can be
used several times a day to treat this.
Ongoing bleeding can be a
problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and
other blood-thinning medicines can make bleeding more likely. If you have
bleeding or clotting problems, or if you take blood-thinning medicine, tell
your doctor before your blood sample is taken.
A renin assay blood test is done to find
the cause of
high blood pressure (hypertension). The time of day
and your position (standing, sitting, or lying down) before the blood sample is
collected, your age, and the level of sodium in your blood all affect the test
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
A renin test is often done at the same time as
an aldosterone test. To learn more, see the topic
A renin stimulation test may
occasionally be done if blood renin levels are low. To prepare for this test,
you will eat a low-sodium diet for 3 days. A blood renin level will be drawn
and a diuretic, usually furosemide (Lasix), will be put in a vein (intravenous)
in your arm. Normally, blood renin levels will increase, but in Conn's syndrome
blood renin levels will not change after taking the diuretic.
hospitals now measure renin activity with the renin direct immunoassay, which
measures the amount of renin in the blood. A plasma renin activity (PRA) test
measures the production of a hormone called angiotensin I rather than renin itself. A renin
direct immunoassay is easier to do and can generally be done instead of the PRA
test. But in some situations (such as pregnancy), PRA results may be more
accurate than the renin direct immunoassay.
How this information was developed to help you make better health decisions.