How It Is Done
The health professional drawing your
- 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 C-peptide test measures the level of
this peptide in the body.
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.
level of C-peptide in the blood must be read with the results of a blood
glucose test. Both these tests will be done at the same time. A test to measure insulin level also may be done.
- High levels of both C-peptide and blood
glucose are found in people with
type 2 diabetes or
insulin resistance (such as from
- A high level of
C-peptide with a low blood glucose level may mean that an insulin-producing tumor of
the pancreas (insulinoma) is present or that the use of certain medicines such
as sulfonylureas (for example, glyburide) is causing the high level.
- If C-peptide levels are high after an insulinoma is taken out,
it may mean that the tumor has returned or that the tumor has spread to other
parts of the body (metastasized).
- Low levels of both C-peptide and blood
glucose are found in liver disease, a severe infection,
Addison's disease, or insulin therapy.
low level of C-peptide with a high blood glucose level is found in people with
type 1 diabetes.
- Complete removal of the
pancreas (pancreatectomy) causes a C-peptide level so low it can't be
measured. The blood glucose level will be high, and insulin will be needed in
order for the person to survive.