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C-Peptide, Fasting

Also referred as

Connecting peptide insulin

Insulin C-peptide

Proinsulin C-peptide

1,510+ booked recently

For men & women

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30 hours

Contains

1 test

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The C-Peptide, Fasting test measures the level of C-peptide in the blood after a period of 8 to 12 hours of fasting. This test evaluates insulin production by the pancreas and helps understand, monitor, or treat disorders such as hypoglycemia (low blood sugar), diabetes, etc.

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Blood

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Why is this test booked?

Preparations

Overnight fasting required for 8 to 12 hours

Sample Collection

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Understanding C-Peptide, Fasting

The C-Peptide, Fasting test is tailored for individuals with diabetes. It helps doctors understand how well the pancreas is making insulin, which is vital for managing the condition effectively. During this test, the level of C-peptide, a protein fragment released when insulin is produced, is measured in the blood after a period of 8 to 12 hours of fasting. C-peptide levels provide valuable information about the body’s own insulin secretion, distinguishing between endogenous insulin (produced by the pancreas) and exogenous insulin (administered externally). This distinction is important in understanding various conditions, particularly diabetes, as this test helps determine whether insulin resistance or impaired insulin secretion is the underlying cause.

The C-Peptide, Fasting test may be required in individuals presenting with symptoms like frequent urination, excessive thirst, or unexplained weight loss suggestive of diabetes. It can also be done if your doctor suspects you have insulin resistance; your diabetes has been incorrectly classified; or you have acute or recurring hypoglycemia without an apparent cause. Additionally, the C-Peptide, Fasting test can be done periodically when you have been diagnosed with an insulinoma (tumor in the pancreas) to monitor the effectiveness of treatment and to detect its recurrence.

Usually, overnight fasting (8 to 12 hours) is required before going for the C-Peptide, Fasting test. However, drinking water is acceptable. Inform your doctor about any medications, supplements, or herbal remedies that you are currently taking as some of them may interfere with the test results and require temporary discontinuation.

Lab test results may vary across different laboratories. Abnormal test results require an expert interpretation; therefore, never try to self-medicate at home based solely on these results, and always consult a doctor for a proper understanding of the test results. The results will help them evaluate your medical condition and formulate an overall treatment plan.

What does C-Peptide, Fasting measure?

The C-Peptide, Fasting test measures the level of C-peptide in the blood. C-peptide is a byproduct of insulin production in the pancreas. When the pancreas releases insulin into the blood, it also releases C-peptide in equal amounts. Therefore, measuring C-peptide levels can provide valuable insights into the body's natural production of insulin. This test is particularly useful in individuals with diabetes, as it helps determine how well their pancreas is functioning in producing insulin.

By assessing C-peptide levels, doctors can better understand an individual's insulin production capacity. This information is crucial for diagnosing and managing diabetes effectively. Additionally, the C-Peptide, Fasting test can help differentiate between type 1 and type 2 diabetes, guide treatment decisions, monitor the effectiveness of diabetes therapies, and evaluate overall pancreatic function Moreover, the C-Peptide, Fasting test plays a vital role in tailoring personalized treatment plans for individuals with diabetes, ensuring optimal management of their condition.

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FAQs related to C-Peptide, Fasting

Why is the C-Peptide, Fasting test performed?

The test is performed to evaluate the production of insulin by the pancreas. It helps distinguish between type 1 and type 2 diabetes, monitor insulin production in individuals with diabetes, and sometimes in the investigation of hypoglycemia (low blood sugar).

Are there any special preparations required before the C-Peptide, Fasting test?

Yes, you must fast for 8-12 hours before taking the C-Peptide, Fasting test. However, you can drink water. Also, inform your doctor about any medications you are taking, as some of them can affect your test results and may need to be adjusted or temporarily discontinued before the test.

What are the risks associated with the C-Peptide, Fasting test?

The risks associated with this test are generally minimal. However, some people may experience mild pain or discomfort at the site from where the blood sample is taken, which is usually self-limiting.

How often should I book the C-Peptide, Fasting test?

The frequency of getting the C-Peptide, Fasting test depends on the individual circumstances and their diabetes status. However, it is best to follow your doctor's recommendations.

Does C-peptide level help in diagnosing diabetes?

C-peptide level may help in differentiating type 1 diabetes from type 2 diabetes, but does not actually help in the diagnosis of diabetes.

What medical conditions can affect C-Peptide levels?

Medical conditions such as type 1 diabetes, type 2 diabetes, insulin resistance, pancreatic tumors, and kidney failure can affect C-Peptide levels.

What is the difference between type 1 and type 2 diabetes?

Type 1 diabetes is an autoimmune condition where the body’s immune system attacks and destroys the insulin-producing cells (islet cells) in the pancreas leading to little or no insulin production. Whereas, in type 2 diabetes, the body becomes resistant to insulin or does not produce enough insulin to maintain normal blood sugar levels.

Is diabetes preventable?

Type 2 diabetes is largely preventable through lifestyle changes such as keeping weight under control, exercising regularly, eating a healthy diet, and avoiding smoking. However, type 1 diabetes is an autoimmune condition, and currently, there is no cure for it.

What other tests might I have along with the C-peptide test?

Additional tests may vary at the doctor's discretion. However, commonly prescribed tests include Blood glucose test, glucagon test, insulin test, and HbA1c test.

Content created by

Dr. Swati Gupta (Anand)

MBBS, MD Lab Medicine

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Last Updated

14th Oct 2025