What Is an
Insulin C-Peptide Test?
Insulin is the hormone that is primarily responsible for lowering
glucose (sugar) levels in the blood. It is produced by beta
cells (specialized cells in the pancreas). When we eat, our bodies
begin to break food down into glucose and other nutrients.
In response to this, the pancreas produces insulin, which allows cells to
absorb glucose from the blood. C-peptide is byproduct created when insulin is
produced. Because of this, measuring the amount of C-peptide in blood indicates
how much insulin is being produced. Generally, high C-peptide production
indicates high insulin production, and vice versa.
Benefits from an Insulin C-Peptide Test?
The insulin C-peptide test (or simply the C-peptide test) is used to monitor
insulin production in the body and determine the cause of hypoglycemia
(low blood sugar). The test is often ordered when someone is newly diagnosed
with type 1 diabetes, to reveal how much insulin the pancreas is producing. It
is also sometimes used to distinguish between type 1 and type 2 diabetes if the
doctor is not sure which type of diabetes is present. It can also provide
information about how well the beta cells in the pancreas are working.
The test may also be performed for patients who experience symptoms related
to hypoglycemia in the absence of type 1 or type 2 diabetes. In this case, the
body may be producing too much insulin. Symptoms of hypoglycemia include:
- heart palpitations
- excessive hunger
- nervousness or irritability
- blurred vision
- seizures and/or loss of consciousness
Does a Patient Prepare for an Insulin C-Peptide Test?
The preparation needed for the insulin C-peptide test depends on a person’s
age and the reason for the test. In some instances, you may be required to fast
for up to 12 hours before the test. Fasting requires that you to not eat or
drink anything but water before the test. You may also need to stop taking
certain medications. Your doctor will provide you with specific instructions
based on your particular medical needs.
How Is an Insulin C-Peptide Test Administered?
The insulin C-peptide test requires a blood sample administered by a
qualified doctor or nurse. The blood is drawn from a vein, typically in the arm
or from the back of your hand. The procedure can cause minor discomfort, but it
will be temporary. The blood will be collected in a tube and sent to a lab for
Results are typically available within a few days. Your doctor will be able
to provide you with more information about the results and what they mean. In
general, normal results for C-peptide in the bloodstream are between 0.5 and
2.0 ng/mL (nanograms per milliliter). However, results for the insulin
C-peptide test may vary based on the lab.
the Risks of an Insulin C-Peptide Test?
The insulin C-peptide test may cause some discomfort when the blood sample
is drawn. Common side effects include temporary pain or throbbing at the
injection site. Less common side effects include:
- difficulty obtaining a sample, resulting in multiple
- excessive bleeding at the needle site
- fainting as a result of blood loss
- the accumulation of blood under the skin, known as a
- infection where the skin is broken by the needle