Book C-Peptide Test: Purpose, Normal Range and Price

The C-Peptide test is a blood test that measures the level of C-peptide, a short protein fragment released by the pancreas in equal amounts alongside insulin during the conversion of proinsulin into active insulin. Because C-peptide is produced in a one-to-one ratio with insulin and is not metabolised by the liver before entering the bloodstream, it provides a more accurate and stable reflection of the pancreas's own insulin production than measuring insulin directly. C-peptide measurement therefore distinguishes between insulin produced by the body and insulin administered externally as an injection. In India, where both Type 1 and Type 2 diabetes are among the most prevalent chronic diseases and where the distinction between diabetes types significantly impacts treatment decisions, the C-Peptide test is an invaluable diagnostic tool. A low or undetectable C-peptide confirms that the pancreas has lost its ability to produce insulin, as seen in Type 1 diabetes and late-stage Type 2 diabetes, while a normal or elevated C-peptide confirms that the pancreas is still producing insulin, pointing toward insulin resistance rather than insulin deficiency as the underlying problem. This distinction directly determines whether a diabetic patient requires lifelong insulin therapy or can be managed with oral medications. The test involves a simple blood draw completed in under five minutes.

Doctors prescribe a C-Peptide test in the following situations: Distinguishing Type 1 from Type 2 diabetes in newly diagnosed patients or in cases where the diabetes type is clinically unclear, particularly in young adults where both types can present similarly and where the correct classification determines long-term treatment strategy. Assessing residual beta cell function in patients with established Type 1 diabetes where the presence of any remaining endogenous insulin production has implications for glycaemic control, hypoglycaemia risk, and eligibility for certain newer therapies. Evaluating patients with Type 2 diabetes who have been on oral medications but are experiencing worsening glycaemic control, where a low C-peptide confirms declining beta cell function and the need to transition to insulin therapy. Investigating hypoglycaemia, particularly unexplained or recurrent low blood sugar episodes, where a high C-peptide alongside low blood glucose suggests endogenous insulin overproduction from an insulinoma, a rare insulin-secreting pancreatic tumour. Detecting exogenous insulin misuse or factitious hypoglycaemia where a low C-peptide alongside high insulin levels confirms that external insulin rather than endogenous production is the cause of hypoglycaemia. Monitoring beta cell function after pancreatic surgery, pancreatitis, or pancreatic transplantation where serial C-peptide measurements track the recovery or preservation of insulin-producing capacity. Evaluating Latent Autoimmune Diabetes in Adults, known as LADA, where a gradual decline in C-peptide over time in a patient initially appearing to have Type 2 diabetes confirms progressive autoimmune beta cell destruction.

The C-Peptide test measures the concentration of C-peptide in the blood, reported in nanograms per millilitre (ng/mL) or picomoles per millilitre (pmol/mL). Normal C-Peptide Range in India The standard reference ranges used across most Indian diagnostic laboratories are as follows. For fasting C-peptide, a normal level is between 0.5 and 2.0 ng/mL. For stimulated C-peptide measured after a meal or glucose load, normal levels typically rise to between 2.5 and 5.0 ng/mL, reflecting the pancreas's capacity to increase insulin secretion in response to glucose. Interpreting C-Peptide Results A fasting C-peptide below 0.5 ng/mL indicates severely reduced or absent beta cell function, consistent with Type 1 diabetes or advanced Type 2 diabetes with significant beta cell exhaustion, and confirms the need for insulin therapy. A fasting C-peptide between 0.5 and 2.0 ng/mL is within the normal range and indicates preserved endogenous insulin production, suggesting Type 2 diabetes with insulin resistance as the primary mechanism rather than insulin deficiency. A fasting C-peptide above 2.0 ng/mL is elevated and may indicate insulin resistance with compensatory hyperinsulinaemia, as commonly seen in obesity and metabolic syndrome, or may raise concern for an insulinoma when accompanied by hypoglycaemia.

Fasting for 8 to 10 hours before the test is recommended for a fasting C-peptide measurement, which is the standard baseline assessment. You may drink water normally during the fasting period. Our team confirms preparation requirements at the time of booking. If a stimulated C-peptide is required, your doctor will provide specific instructions regarding a glucose load or standardised meal before the test. Do not eat or drink anything other than water until instructed. Inform the phlebotomist about all diabetes medications you are currently taking, particularly insulin injections, sulphonylureas, and GLP-1 receptor agonists, as these directly influence insulin secretion and C-peptide levels and must be disclosed for accurate interpretation. Inform your doctor if you have significant kidney disease, as C-peptide is cleared by the kidneys and impaired renal function causes C-peptide to accumulate in the blood, producing falsely elevated results. Stay normally hydrated before sample collection.

If you are booking through the SecondMedic platform the C-Peptide test price starts at approximately Rs. 1,199. The exact price will be confirmed at the time of booking through SecondMedic. If your doctor has prescribed multiple tests alongside C-Peptide, SecondMedic health packages include C-Peptide as part of a broader diabetes evaluation or pancreatic function panel at a significantly lower combined price.

SecondMedic provides home sample collection for C-Peptide test across all major areas of India. You do not need to visit a lab or collection centre. A certified and trained phlebotomist comes to your home or workplace at your chosen time, collects the sample using sterile single-use equipment, and ensures it is transported to the NABL-accredited lab within the required time window for accurate processing. Please note that SecondMedic provides free home sample collection on all tests priced above Rs. 300. Our team will check your pincode and confirm if your address falls under our free sample collection eligibility criteria, which depends upon the lab location and phlebotomist availability. Home collection is available between 7 AM and 10 PM, seven days a week, including Sundays and public holidays. Enter your pincode on the booking page or call our helpline to confirm availability at your address.