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Intel Lab Diagnostics Dubai
Single Biomarker

C-Peptide, Fasting

Insulin Production Marker

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.

BLOOD24 HOURSFASTING
AEDAED250
  • Free home collection
  • Physician-reviewed report

24 Hours

Turnaround

Blood

Sample

About This Test

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.

Sample type
Blood
Turnaround
24 Hours
Fasting
Required
Best for
Adults at metabolic risk
Why Get Tested?

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.

When This Test Is Ordered

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.
Preparation
The short version
A little prep.
  • Blood
  • Free home collection
  • Fasting required
  • Results in 24 Hours
  1. 1
    Book any time

    Pick a morning slot online or on WhatsApp: come fasted per the prep note below.

  2. 2
    We come to you

    A DHA-licensed nurse collects your sample at home or in the office: free home collection.

  3. 3
    Results in 24 Hours

    A physician-reviewed, easy-to-read report lands securely by WhatsApp and email.

Prep note
Physician reviewed

This test requires fasting.

Have nothing but plain water overnight before the sample, ideally taking it early in the morning so the fast is comfortable, and eat normally in the days before rather than restricting food. Do not take your morning insulin, tablets for diabetes or any medicine that stimulates insulin release before the sample unless your doctor has specifically told you to; ask in advance and bring them with you to take afterwards.

Ask for a glucose sample to be taken at the same time, since the two results are read together. Mention any kidney problem, steroid treatment or recent illness, and avoid alcohol the evening before.

Reading a High or Low Result

  • 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.

Limitations & Safety

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.
Key Points
  • 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

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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.