Martina Feichter

Martina Feichter studied biology in Innsbruck with an optional subject in pharmacy and also immersed herself in the world of medicinal plants. From there it was not far to other medical topics that still captivate her today. She trained as a journalist at the Axel Springer Academy in Hamburg and has been working for lifelikeinc.com since 2007 - first as an editor and since 2012 as a freelance author.

More about the lifelikeinc.com experts C-peptide is a byproduct of insulin production. The pancreas produces proinsulin, a precursor hormone that is split into the active, hypoglycemic hormone insulin and the C-peptide. Find out how much the C-peptide value is normally and what changed readings mean.

ArtikelübersichtC peptide

  • What is the C-peptide?
  • When do you determine the C-peptide?
  • normal values
  • When is the C-peptide lowered?
  • When is the C-peptide increased?
  • What to do if the C-peptide is elevated or decreased?

What is the C-peptide?

The C-peptide is produced in the pancreas in the formation of insulin: The so-called beta-cells produce the inactive precursor proinsulin. It is split to activate it - into the blood sugar-lowering hormone insulin and the C-peptide. The term stands for Connecting Peptide, because it combines the building blocks of proinsulin.

Unlike insulin, C-peptide degrades much more slowly, making it an ideal measure of pancreatic function and insulin production.

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When do you determine the C-peptide?

In the laboratory, the C-peptide value is mainly determined to evaluate the performance of pancreatic beta cells. If the beta cells are able to produce insulin, C-peptide can also be detected. An assessment of pancreatic performance is also important for treatment planning in diabetes - that is, when deciding whether a diabetic needs to inject insulin or not.

Sometimes it is necessary to measure both the C-peptide value as well as the insulin value and the blood sugar level. If the doctor suspects a proinsulin-producing tumor (insulinoma), blood samples are taken from the patient at regular intervals while he is starving. If high C-peptide levels and insulin levels are detected in the blood, although too little glucose is present in the blood (hypoglycaemia), this is considered clear evidence of an insulinoma. Possible signs of this usually benign tumor of the pancreas, for example, confusion, weakness and seizures, dizziness, weight gain and cravings.

Very rarely, a hypoglycaemia can diagnose a so-called hypoglycaemia factitia. It is a mental illness in which patients purposely lower blood sugar levels with insulin. The victims usually want to gain more attention and attention from doctors, hospitals or relatives. In this particular case, the C-peptide level is normal, while the insulin is too high and the blood sugar too low. If the patient uses sulfonylureas to reduce blood sugar, C-peptide and insulin are elevated.

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C-peptide - normal values

As a rule, the laboratory value is measured in the fasting state. The following standard values ​​apply:


C-peptide: norm

12-hour fasting

0.7-2.0 μg / l

longer fasting

<0.7 μg / l

Maximum values ​​under glucose or glucagon stimulation

2.7 - 5.7 μg / l

Glucose or glucagon stimulation is performed to assess whether a diabetic patient needs to inject insulin. Glucose or glucagon are administered to the patient before the C-peptide level is measured.

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When is the C-peptide lowered?

The C-peptide is naturally degraded if the pancreas does not have to produce insulin, so the blood sugar level is low and you have not eaten.

Due to illness, the laboratory value is too low when insulin production is limited - ie in diabetes mellitus. In type 1 diabetes mellitus, which occurs especially at a young age, autoantibodies attack the beta cells and destroy them so they can no longer produce proinsulin. In type 2 diabetes mellitus, the C-peptide level is not lowered until the late stage when pancreatic insulin production fails.

Other possible causes of a decreased C-peptide include Addison's disease and the administration of certain medications (alpha-sympathomimetics).