Biomarkers · Vitamins & Endocrine

C-peptide

Lower values go with lower risk of death. Not measured in our NHANES panel. The curve is drawn from the published study (source below).

C-peptide and risk of death

Published curve higher than the NHANES fitNHANES fit higher

Risk of death relative to the curve's reference value, drawn from the published study (source below).

Published risk of death1.80×highest vs lowest quartile of serum C-peptide (95% CI 1.33–2.43) · NHANES III participants aged 40 years and older without history of diabetes, linked mortality file, USA

C-peptide by age and sex

Each bar runs from the 5th to the 95th percentile, the darker part from the 25th to the 75th, and the tick is the median. Not a reference range or a target.

The percentiles as a table

Each row is one sex and age band: the values below which 5%, 25%, 50%, 75% and 95% of people fall (ng/mL), from the survey named in the row. Not a reference range or a target.
Sex	Age	5th	25th	Median	75th	95th	n	Cycle / source
All	20-39	1.06	1.50	2.01	2.81	4.85	628	NHANES 2003-2004
All	40-59	1.11	1.69	2.37	3.21	5.02	595	NHANES 2003-2004
All	60+	1.21	1.91	2.66	3.55	5.27	804	NHANES 2003-2004
All	all	1.10	1.66	2.29	3.18	5.03	2,027	NHANES 2003-2004
Men	20-39	1.13	1.54	2.03	2.88	5.14	353	NHANES 2003-2004
Men	40-59	1.14	1.80	2.51	3.35	5.04	288	NHANES 2003-2004
Men	60+	1.37	2.15	2.87	3.64	5.35	393	NHANES 2003-2004
Men	all	1.16	1.75	2.40	3.32	5.13	1,034	NHANES 2003-2004
Women	20-39	1.04	1.47	1.97	2.70	4.81	275	NHANES 2003-2004
Women	40-59	1.05	1.61	2.26	3.02	4.87	307	NHANES 2003-2004
Women	60+	1.17	1.79	2.50	3.38	5.23	411	NHANES 2003-2004
Women	all	1.05	1.58	2.17	3.00	4.95	993	NHANES 2003-2004

What studies found when this marker was changed

They describe what happened in those study groups, not a recommendation. See all catalogued interventions.

Measured changes in C-peptide, study by study

1 effect with a numeric size, each from one study arm: the dot is the reported change, the line its 95% interval where one was given. Green points move the marker the way lower risk of death lies; amber the other way. Study results in the groups studied, not predictions for a person.

Each row is one study: what was changed, the effect it reported on this marker, and the source.
Type	Intervention	Reported effect	Evidence	Source
supplement	Oral nicotinamide (vitamin B3) started at diagnosis of insulin-dependent diabetes, in addition to insulin, continued for 1 year	Basal C-peptide 0.73 vs 0.32 ng/mL in controls one year after diagnosis (P < 0.005)	meta-analysis	Pozzilli P, et al. Diabetes Care. 1996. Meta-analysis of nicotinamide treatment…

Things that worsen it

Each row is one study: what was changed, the effect it reported on this marker, and the source.
Type	Condition or exposure	Reported effect	Evidence	Source
pharmacologic	Combination sulfonylurea plus insulin therapy for >=8 weeks in insulin-treated adults with non-insulin-dependent (type 2) diabetes	Fasting C-peptide rose from 1.45 to 1.75 ng/mL with combined therapy vs 1.42 to 1.30 ng/mL with insulin alone (effect size 0.26, P<0.017)	meta-analysis	Pugh JA, et al. Diabetes Care. 1992. Is combination sulfonylurea and insulin…

Sources

Risk curve: Min JY 2013 (PMID 23589428): all-cause HR 1.8 (1.33-2.43) highest vs lowest quartile of serum C-peptide. Scaled to US values (NHANES).
Min JY, Min KB. Serum C-peptide levels and risk of death among adults without diabetes mellitus. CMAJ (Canadian Medical Association Journal). 2013;185(9):E402-E408.

Map C-peptide against another biomarker.

Map C-peptide against another marker