Low levels of C-peptide have clinical significance for established Type 1 diabetes

Diabet Med. 2015 Oct;32(10):1346-53. doi: 10.1111/dme.12850. Epub 2015 Aug 16.


Aim: To determine whether the low C-peptide levels (< 50 pmol/l) produced by the pancreas for decades after onset of Type 1 diabetes have clinical significance.

Methods: We evaluated fasting C-peptide levels, duration of disease and age of onset in a large cross-sectional series (n = 1272) of people with Type 1 diabetes. We then expanded the scope of the study to include the relationship between C-peptide and HbA1c control (n = 1273), as well as diabetic complications (n = 324) and presence of hypoglycaemia (n = 323). The full range of C-peptide levels was also compared with 1,5-Anhydroglucitol, a glucose responsive marker.

Results: C-peptide levels declined for decades after diagnosis, and the rate of decline was significantly related to age of onset (P < 0.0001), after adjusting for disease duration. C-peptide levels > 10 pmol/l were associated with protection from complications (e.g. nephropathy, neuropathy, foot ulcers and retinopathy; P = 0.03). Low C-peptide levels were associated with poor metabolic control measured by HbA1c (P < 0.0001). Severe hypoglycaemia was associated with the lowest C-peptide levels compared with mild (P = 0.049) or moderate (P = 0.04) hypoglycaemia. All levels of measurable C-peptide were responsive to acute fluctuations in blood glucose levels as assessed by 1,5-Anhydroglucitol (P < 0.0001).

Conclusions: Low C-peptide levels have clinical significance and appear helpful in characterizing groups at-risk for faster C-peptide decline, complications, poorer metabolic control and severe hypoglycaemia. Low C-peptide levels may be a biomarker for characterizing at-risk patients with Type 1 diabetes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Blood Glucose / metabolism
  • C-Peptide / blood*
  • Child
  • Cross-Sectional Studies
  • Deoxyglucose / blood
  • Deoxyglucose / metabolism
  • Diabetes Mellitus, Type 1 / blood*
  • Diabetes Mellitus, Type 1 / complications
  • Diabetes Mellitus, Type 1 / diagnosis*
  • Diabetes Mellitus, Type 1 / epidemiology
  • Glycated Hemoglobin / metabolism
  • Humans
  • Middle Aged
  • Prognosis
  • Young Adult


  • Blood Glucose
  • C-Peptide
  • Glycated Hemoglobin A
  • 1,5-anhydroglucitol
  • Deoxyglucose