Questions about fasting or a stimulated sample? Call 8872524007.
What the C-Peptide test checks
The pancreas makes insulin from a larger molecule called proinsulin. When proinsulin splits, it releases one molecule of insulin and one of C-peptide ("connecting peptide"). So C-peptide levels mirror your own insulin output.
Injected insulin contains no C-peptide. That makes this the cleaner measure of natural insulin production in people already on insulin therapy. C-peptide also lasts longer in the blood than insulin, so levels are steadier.
Why your doctor may order it
- To help tell type 1 from type 2 diabetes, or spot slower-onset autoimmune diabetes in adults
- In younger patients where a genetic form of diabetes is being considered
- Before deciding whether someone on insulin could manage on tablets
- When investigating unexplained low blood sugar, alongside glucose and insulin
- After pancreatic surgery or disease
How to prepare
Your doctor will say whether they want a fasting or a stimulated sample. A fasting sample needs 8 to 10 hours without food, water only. A stimulated sample is taken after a meal or a set drink at a time your doctor specifies, sometimes paired with a PPBS test.
A glucose reading is usually taken at the same time, because C-peptide is read against the sugar level. Keep taking your medicines unless your doctor says otherwise, and tell us what you use, including biotin supplements. The blood test preparation guide covers fasting basics.
Sample type and report time
Blood is drawn into a serum tube and separated promptly. The sample is collected at Alpha Laboratory and processed in-house or at a partner reference laboratory, depending on the test. Reports are usually ready in 1–3 working days; we'll tell you the expected date when you book.
If you're searching for a C peptide test near me and can't travel, ask about home sample collection for a fasting morning sample.
Understanding your results
Results are usually given in ng/mL. A low C-peptide with high glucose suggests the pancreas makes little insulin, as in type 1 diabetes or long-standing type 2. A normal or high value with high glucose fits insulin resistance.
During low blood sugar, a high insulin with a low C-peptide raises the question of injected insulin, while both being high points towards the body's own excess production. Kidney disease raises C-peptide because the kidneys clear it. The range printed on your report is the one that applies, ranges vary by lab and method, and your doctor reads the result alongside your symptoms and other tests.
FAQ
What's the difference between C-peptide and insulin tests?
Both reflect insulin production, but C-peptide isn't affected by injected insulin and stays in the blood longer. For people on insulin, C-peptide is more useful.
Do I need to fast?
Usually yes for a fasting sample. Some doctors ask for a sample after a meal instead; follow your slip.
Why does my report take longer than a sugar test?
C-peptide is a specialised hormone test. It may be processed at a partner reference laboratory, so allow 1–3 working days.
Can kidney disease affect C-peptide?
Yes. Reduced kidney function can raise C-peptide, so doctors check kidney results when reading it.
Book at Alpha Laboratory
Book your C-peptide test by calling 8872524007 or WhatsApp us the slip so we can confirm fasting or stimulated timing. Find us via the contact page.