C-Peptide, Fasting
C-peptide is released in equal amounts to insulin when the pancreas produces it, so a fasting level reflects how much insulin your body makes on its own. Useful for assessing beta-cell function and insulin resistance.
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24 hours
Turnaround
Blood
Sample
What the C-Peptide, Fasting test tells you
When the pancreas makes insulin, it first builds a larger precursor molecule and then cuts it in two. One half is insulin itself; the other is a fragment called C-peptide. The two are released into the blood together, in equal amounts, every time insulin is secreted. C-peptide is cleared from the circulation more slowly than insulin and is not removed by the liver on its first pass, so its level gives a steadier, less flickering picture of how much insulin the pancreas is actually producing.
The practical advantage is decisive: insulin given by injection or pump contains no C-peptide. Measuring insulin directly in someone who is treated with insulin tells you almost nothing about their own production, because the assay cannot separate what the body made from what was injected. C-peptide can, which is why it is the standard way to judge how much natural insulin production remains. Measured while fasting, alongside a glucose sample taken at the same moment, it helps a doctor work out what kind of diabetes is present and how much pancreatic reserve is left. A low result with a high glucose suggests the insulin-producing cells are failing, the pattern seen in type 1 diabetes and in long-standing type 2 diabetes. A high result with a high glucose suggests the opposite problem: plenty of insulin is being made, but the body is responding poorly to it.
The same test is used from the other direction when blood sugar drops unexpectedly low. If C-peptide is high at a moment when glucose is low, the insulin causing it came from the person's own pancreas, whether because of a rare insulin-producing tumour or because of a medicine that stimulates the pancreas. If C-peptide is suppressed while glucose is low, the insulin came from outside the body. One important caveat runs through all of this: C-peptide is cleared by the kidneys, so reduced kidney function raises the level independently of how much insulin is being made, and results must be read with kidney function in mind.
Measured after an overnight fast to show how much insulin your own pancreas is still making, even while you are taking insulin. It helps your doctor classify diabetes, judge how much pancreatic reserve is left, and investigate unexplained low blood sugar.
- Separating own from injected insulin
Injected insulin contains no C-peptide, so this is the practical way to see how much insulin a treated person still makes for themselves.
- Judging pancreatic reserve
The result shows how much insulin-producing capacity remains, which influences whether tablets are likely to work or insulin is needed.
- Clarifying the type of diabetes
When the picture does not fit neatly into type 1 or type 2, this measurement is one of the tests that helps sort it out.
- Investigating low blood sugar
In unexplained hypoglycaemia, the result distinguishes insulin the body produced itself from insulin that came from outside.
Reasons your doctor may request the C-Peptide, Fasting test
Your doctor may order this test for any of the reasons below. Some are routine checks, others follow specific symptoms or an earlier result.
Clarifying the type of diabetes
- Diabetes that does not fit clearly into type 1 or type 2 on clinical grounds alone.
- Assessment of how much natural insulin production remains in someone already treated with insulin.
Choosing treatment
- Deciding whether tablet treatment is a realistic option or insulin will be required.
Low blood sugar & insulin resistance
- Investigation of repeated unexplained episodes of low blood sugar.
- Assessment of insulin resistance alongside fasting glucose in someone with metabolic risk factors.
A result in the Normal band, 0.8 to 3.8 ng/mL on a fasting sample, indicates the pancreas is making insulin at a typical rate. C-peptide is released in equal amounts with the body's own insulin, so it shows how much insulin you produce even if you also inject insulin. A result in the Low band, below 0.8 ng/mL, suggests reduced insulin production, as in type 1 diabetes, long-standing type 2 diabetes or damage to the pancreas; a very low value at a time of low blood sugar suggests the insulin came from outside the body. A result in the High band, above 3.8 ng/mL, usually reflects insulin resistance, where the pancreas works harder to control blood sugar, as seen with obesity, prediabetes and early type 2 diabetes; rarely it points to an insulin-producing tumour. The kidneys clear C-peptide, so reduced kidney function raises it. Your doctor reads it with a glucose measured at the same time, HbA1c and any diabetes antibody tests.
Medically reviewed by Dr Nirupama Sabhapathy
Ranges are a guide: your physician interprets your result alongside your symptoms and history.
What a higher result can point to
- Insulin resistance, in which the pancreas produces extra insulin to overcome poor tissue response.
- Earlier-stage type 2 diabetes, where insulin output is still high or even increased.
- Medicines that stimulate the pancreas to release insulin, such as sulfonylureas.
- Reduced kidney function, which slows clearance and raises the level without extra production.
- A rare insulin-producing tumour of the pancreas, typically found while investigating low blood sugar.
What a lower result can point to
- Type 1 diabetes, in which the immune system has destroyed the insulin-producing cells.
- Long-standing type 2 diabetes in which the pancreas has gradually lost capacity.
- Disease of the pancreas itself, including chronic inflammation or surgical removal of part of the gland.
- Treatment with injected insulin, which reduces the pancreas's own output.
- Prolonged fasting or very low food intake, when insulin secretion is naturally switched down.
These are possibilities, not diagnoses. A single value outside the reference range is interpreted alongside your symptoms, history and other tests: your doctor decides what it means for you.
What this test cannot tell you
- The result is difficult to interpret without a glucose sample taken at the same moment, because the same value means different things at a high and a low blood sugar.
- Reduced kidney function raises the level regardless of insulin production, so kidney results are needed to read it properly.
- It describes how much insulin is being produced, not how well the body responds to it, so it does not replace the clinical assessment or the other tests used to classify diabetes.
Risks of the blood draw
- Mild bruising or brief soreness where the needle went in.
- Occasional lightheadedness, which settles after a few minutes of rest.
- Bleeding or infection at the site, which is rare with sterile single-use equipment.
- 1C-peptide and insulin are released together in equal amounts, so one is a reliable stand-in for the other.
- 2Injected insulin contains no C-peptide, which is what makes this test able to measure your own production.
- 3It should be interpreted alongside a glucose measured on the same sample.
- 4Kidney function must be taken into account, since the kidneys clear this fragment.
- 5The result informs how diabetes is classified and treated; it is not a diagnosis in itself.
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Frequently Asked Questions
Everything you need to know about the C-Peptide, Fasting test. Can't find what you're looking for?
Talk to our team→Two reasons. Insulin is partly removed by the liver as soon as it is released, so blood insulin fluctuates more; and if you take insulin by injection or pump, an insulin measurement cannot distinguish that from your own. C-peptide is produced only by your pancreas, so it reflects your own output.
It suggests that the insulin-producing cells have limited capacity left, a pattern seen in type 1 diabetes and in type 2 diabetes of long duration. It often has practical consequences for treatment, but the conclusion belongs to your doctor, who reads it with your glucose, your history and other tests.
The kidneys are the main route by which this fragment leaves the blood. When kidney function is reduced it accumulates, so the level can look high even when the pancreas is producing normally. Your doctor allows for this when interpreting the result.
Ask your own doctor, and do not decide alone. Some medicines directly stimulate insulin release and will change the result, so they are often delayed until after the sample. Insulin doses in particular should never be altered without advice.
It measures C-peptide in a fasting serum sample, reported in ng/mL. The pancreas releases this fragment in equal amounts alongside the insulin it makes, while injected insulin contains none, so the level reflects your own insulin output. It is read with a glucose taken at the same time and with kidney function in mind, since the kidneys clear it.
It is useful when diabetes is hard to classify as type 1 or type 2, or when you already take insulin and want to know how much your pancreas still produces. That can help your doctor decide whether tablets are a realistic option. It is also used to investigate unexplained low blood sugar and to assess insulin resistance when metabolic risk factors are present.
Yes. We recommend fasting for 10-12 hours before your Insulin Production Marker test; plain water is fine. No special preparation required.
The Insulin Production Marker test uses a blood sample, collected quickly by our DHA-licensed phlebotomist with minimal discomfort.
Results for the Insulin Production Marker test are typically ready within 24 hours. You will receive a secure digital report, and your Smart Report highlights anything outside the normal range.
The Insulin Production Marker test is AED 90, which includes a physician-reviewed report. Home collection is free when your order comes to AED 300 or more or includes a package; below that, an AED 100 home collection fee applies (AED 50 for a lab walk-in). You can also build a custom panel and pay only for the markers you choose.
Yes. A DHA-licensed phlebotomist can collect your sample at home or the office anywhere in Dubai, 7 days a week. Collection is free for orders of AED 300 or more, or any order with a package; otherwise an AED 100 home collection fee applies. See how it works.
It is commonly chosen by adults at metabolic risk. If you are not sure it is right for you, our care team is happy to advise.
Add the Insulin Production Marker test to your cart and complete the short booking wizard, choosing home collection or a lab visit. Guest checkout lets you book without creating an account.
Yes. It is processed at our EIAC-accredited laboratory (ISO 15189:2022) under DHA license 0046381 and verified by board-certified pathologists.
Every report includes reference ranges and plain-language notes. If you have questions, our care team can arrange a clinician review: just get in touch.
Absolutely. Add it to a curated health package or bundle it with any of our 160+ biomarkers, often from a single sample in one visit.