YES — C-peptide is often a better marker of long-term insulin secretion than insulin itself. Here’s why:
C-Peptide vs. Insulin — What’s the Difference?
| C-Peptide |
Insulin |
| Made 1:1 with insulin (split from proinsulin) |
Active hormone regulating blood sugar |
|
Longer half-life (~30 min) |
Short half-life (~5 min) |
| Not cleared by liver |
Cleared mostly by liver
|
| More stable levels in blood |
More fluctuations due to meals, stress |
| Unaffected by exogenous insulin |
Includes external insulin if taking it
|
Why C-Peptide Is Better for Long-Term Insulin Trends:
- More Stable → Reflects Average Secretion Better
- Because of its longer half-life, C-peptide gives a smoother picture of insulin production over time.
- No Liver Confounding
- Insulin gets processed by the liver first, so its levels can vary a lot.
- C-peptide bypasses that — you see true pancreatic output.
- Best for Endogenous Insulin
- Especially useful if you’re not on insulin therapy — helps distinguish between insulin resistance vs. low production.
- Can Indicate Beta-Cell Health
- Low C-peptide = poor insulin production (e.g., Type 1 or advanced Type 2 diabetes).
- High C-peptide = overproduction (e.g., insulin resistance, early Type 2).
When Insulin Might Be More Useful:
- In dynamic tests (e.g., fasting insulin + glucose for HOMA-IR).
- When looking at acute responses (e.g., post-meal spikes).
TL;DR:
-
C-peptide = more stable, long-term marker of insulin production.
- Best for tracking beta-cell function over time.
-
Insulin = better for short-term, dynamic insulin action.
Do you have recent C-peptide or insulin labs? I can help interpret them in context — especially if you’re watching for insulin resistance vs. beta-cell fatigue.
4o
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