General
C-Peptide Test
Lab test

C-Peptide Test

Ordered to determine how much insulin the pancreas is producing — useful when the type of diabetes is unclear, when LADA is suspected, or when residual pancreatic function needs to be assessed in someone already on insulin. Fasting required. Results reviewed by a General Medicine clinician.

Receive actionable insights and deep analysis—not just lab values– in as little as 48 hours

Clear guidance, and follow-up care available

Simple, online scheduling for labs and everything else

Most insurance accepted

Board-certified

No hidden fees

Available nationwide

What is a C-Peptide Test?

The C-Peptide test measures a byproduct released in equal amounts to insulin when the pancreas produces it — making it the most reliable way to assess how much insulin the body is actually making. Unlike insulin itself, C-peptide is not affected by injected insulin, making it uniquely useful for evaluating pancreatic function even in people already on insulin therapy.

Type 1 vs. type 2 diabetes differentiation

Low or absent C-peptide confirms that the pancreas is producing little or no insulin — consistent with type 1 diabetes or LADA. Normal or elevated C-peptide with high blood sugar points to type 2 diabetes or insulin resistance, changing both the diagnosis and treatment approach.

Residual pancreatic function in insulin users

Because exogenous insulin doesn't affect C-peptide levels, this test can accurately measure how much insulin the pancreas is still producing in people already using insulin therapy — information that influences treatment decisions and prognosis.

Diagnosis of insulinoma

Inappropriately elevated C-peptide alongside low blood sugar can indicate an insulin-producing tumor (insulinoma) — a rare but important cause of recurrent hypoglycemia that C-peptide testing helps identify.

Complete insights in as little as 48 hours

1

Book your test

Instantly schedule at 2,000+ labs nationwide, at a time that works for you. Most visits take 15 minutes or less, with both walk-ins and appointments available.

2

Get results in 48 hours

Your results are delivered quickly—and reviewed by medical professionals. You’ll get clear explanations, robust health insights, and recommended next steps tailored to your health needs.

3

Take action with physician guidance

Choose to review your results and manage your plan with a General Medicine physician—or simply use the insights on your own.

4

Track progress over time

Repeat annually to see trends, improvements, and new emerging risks or book individual tests that focus on your set goals

All your care in one place. That’s the General Medicine difference.

We help you understand your options, connect you to the right clinicians, manage prescriptions, coordinate any needed evaluations, and keep an eye on your overall health along the way. It’s comprehensive care that looks at the full picture — your goals, your history, your lifestyle — and makes it simple to move forward with confidence.

Your care plan
Clinician

What's included

Test type

Blood sample

Collection method

Venipuncture

Fasting

Required

Results processing time

1 to 2 days

C-Peptide

A marker of insulin production in the pancreas. Helps differentiate between type 1 and type 2 diabetes.

Virtual visit with clinician

Ongoing support, always available.

You’ll be supported by experienced clinicians who care for a wide range of health needs, from everyday concerns to more complex conditions.

Our clinicians track your progress over time and adjust your care as needed. If medication is prescribed, we’ll manage dosing and monitor for side effects. If lab testing is recommended, we review results and refine your plan accordingly. You’re never left to navigate care on your own.

What our customers have to say

Hear from people who felt heard, understood, and supported on General Medicine.

“I found the ease of setting the appointment and how quickly I was able to be seen to be amazing. The physician was very friendly and amazingly helpful.”

Natalie, Texas

“The chat visit was super convenient. The doctor was friendly and took the time needed to answer any questions I had. The prescription I needed was called in and ready the same afternoon.”

Dustin, Tennessee

“I loved my General Medicine experience. It gave me peace of mind to know someone cared and I felt they listened to what I was saying.”

Ann, Florida

“General Medicine is easily the most approachable, efficient, high-quality, and responsive care team I've had the pleasure of working with.”

John, Utah

“General Medicine helped me get the imaging and blood work I needed, referred me to the right specialists, and even helped me find a new family doctor.”

Bridget, Mississippi

Order your lab today.

Frequently asked questions

What is C-peptide and what does this test measure?

C-peptide is a byproduct of insulin production in the pancreas. Measuring C-peptide reveals how much insulin your body is actually making — helping distinguish type 1 diabetes (low or absent C-peptide, indicating little to no insulin production) from type 2 diabetes (normal or elevated C-peptide).

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

Yes — fasting for 8 hours is standard for a baseline C-peptide measurement. A stimulated test (using glucagon or a meal) may be ordered in some cases to assess insulin secretory capacity more fully.

Why would a clinician order C-peptide instead of just measuring insulin?

C-peptide has a longer half-life in the blood than insulin, making it a more stable and reliable measure of insulin production. It also isn't affected by injected insulin — making it the preferred marker for people already on insulin therapy to assess residual pancreatic function.

Can this test help determine which type of diabetes I have?

Yes — it's one of the most useful tools for distinguishing type 1 from type 2 diabetes, particularly in adults where the presentation may be ambiguous (LADA — latent autoimmune diabetes of adults — is a common scenario). Low C-peptide with positive autoantibodies points strongly to type 1 or LADA.

Is this test useful for people already on insulin therapy?

Yes — because exogenous (injected) insulin doesn't affect C-peptide levels, this test can measure how much insulin the pancreas is still producing even in people using insulin treatment.
Logo

© 2026 Path Healthcare Systems Corp.