C peptide, also known as connective peptide, is an insulin-producing protein that helps the body move sugar (glucose) into your cells. It’s produced by your body’s beta cells and can be tested in blood or urine.
Tests for c peptide can help doctors know how well a person’s diabetes treatment is working. It can also help determine if a person needs insulin, or if another medicine will work better in their specific situation.
How a C-peptide test works
Your doctor takes a blood sample or uses a 24-hour urine sample during the test. Sometimes, the blood is drawn from a vein in your arm or the back of your hand. You may feel a slight sting or prick when the needle goes in.
The result of the test tells your doctor how much insulin your body is making. A high result indicates that your body is producing too much insulin. This can cause your blood sugar to be too high, which can lead to health problems.
You may need to fast for about 12 hours before the test, and your provider may ask you to stop taking certain medicines that could affect your results. Your doctor will provide you with the instructions you need based on your specific medical needs.
C-peptide tests are used to diagnose and monitor people with type 1 diabetes or type 2 diabetes. They can also be used to check if someone has other conditions that might make it harder for their body to produce insulin.