LabInformationLab tests, explained

C-Peptide, Blood Test in California

This page explains the c-peptide, blood test, what it measures, and how to arrange it. A C-peptide blood test measures a substance your pancreas releases when it makes insulin. Because C-peptide and insulin are released together, this test helps show how much insulin your body is producing. It is often ordered when a doctor is evaluating low blood sugar, distinguishing types of diabetes, or checking how well the pancreas is working. Across California, part of Pacific, the c-peptide, blood test can be ordered directly and collected at a certified site — no referral required.

Sample type
blood
Category
Metabolic & Glucose
Turnaround
1-3 business days
Price
$198
Referral
Not required

A C-peptide blood test measures a substance your pancreas releases when it makes insulin. Because C-peptide and insulin are released together, this test helps show how much insulin your body is producing. It is often ordered when a doctor is evaluating low blood sugar, distinguishing types of diabetes, or checking how well the pancreas is working.

What it measures

  • C-peptide — The main marker; reflects how much insulin your pancreas is releasing.
  • Glucose — Often measured at the same time to compare blood sugar with insulin production.
  • Insulin — Sometimes checked alongside C-peptide for a fuller picture of insulin activity.
  • Hemoglobin A1c — A longer-term average of blood sugar, sometimes added for context.

Who it is for

A doctor may order this test if you have symptoms of low blood sugar, have diabetes that is hard to classify, or are being checked for a pancreas or insulin-related condition. It is not a routine screening test for most people.

Preparation

Your doctor may ask you to fast for 8 to 12 hours before the test, depending on what else is being measured. If no fasting is needed, you can eat and drink normally. Follow the specific instructions you are given.

Results and what they mean

Results are reported as a C-peptide level, usually in nanograms per milliliter, along with any other markers measured. Your clinician interprets the number together with your symptoms, glucose level, and medical history. This is general information only and is not medical advice; discuss your results with a qualified clinician.

Requesting the C-Peptide, Blood Test in California

Order online, choose a certified collection site in California, and review results through a secure portal. No referral is required, and orders are processed confidentially. With coastal metros, inland towns, and rural counties with very different access to testing, it pays to schedule your collection in advance.

Frequently asked questions

Do I need to fast for a C-peptide test?

Sometimes. Fasting is often requested, but it depends on your doctor's instructions and whether other tests are being done at the same time.

Does this test diagnose diabetes?

It is not used alone to diagnose diabetes. It helps show how much insulin your pancreas is making, which can support a diagnosis your clinician is already evaluating.

Can I take my usual medications?

Ask your doctor first. Some medicines can affect insulin and C-peptide levels, so your clinician may adjust timing or give specific guidance.

How long until results are ready?

Typical turnaround is about 1 to 3 business days, though this can vary by laboratory.

C-Peptide, Blood Test by city in California

All testing in California →   Full C-Peptide, Blood Test guide →