C-Peptide · low result
What does a low C-Peptide mean?
Short answer
Low C-peptide means the pancreas is producing little insulin. With high glucose it indicates insulin deficiency — type 1 diabetes, late-stage type 2, pancreatitis or pancreatectomy — and helps decide whether insulin therapy is needed. With normal glucose after a long fast it can simply reflect appropriate suppression. Samples must be handled promptly; delays lower it.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
What is the normal range for C-Peptide?
- age 18+: 1.10 – 4.40 ng/mL
Full reference table, citations and testing options: C-Peptide biomarker page.
What are the common causes of low C-Peptide?
- Type 1 diabetes (including LADA in adults)
- Long-standing type 2 diabetes with beta-cell exhaustion
- Chronic pancreatitis, pancreatic surgery, cystic fibrosis
- Prolonged fasting (appropriately low)
- Delayed sample processing
What symptoms go with low C-Peptide?
- Thirst, urination, weight loss, fatigue when glucose is high
- None when glucose is normal
What do clinicians usually check next?
- Glucose and A1c at the same draw
- GAD-65 and other islet antibodies if type 1/LADA is possible
- Endocrinology review for insulin decisions
Follow-up tests available at TestWell: Glucose ($14.99).
How do you recheck C-Peptide?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Pre-Diabetes Panel | Panel · 5 tests | $89.99 | Yes | 2–5 business days |
| Total Body Panel | Panel · 49 tests | $499.99 | Yes | 5–10 business days |
| C-Peptide | Test | $29.99 | Yes | 2–4 business days |
Common questions
Can C-peptide tell type 1 from type 2 diabetes?
Largely yes. Low C-peptide with high glucose suggests type 1 or insulin-deficient diabetes; normal or high C-peptide suggests type 2. Antibodies complete the picture.
Sources
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.