Blood intermediary metabolite and insulin concentrations after an overnight fast: reference ranges for adults, and interrelations.

Concentrations of several metabolites in deproteinized blood and plasma were determined in 100 subjects after an overnight fast, to establish reference ranges. Blood glycerol, nonesterified fatty acids, and ketone body concentrations and the 3-hydroxybutyrate/acetoacetate ratio increased with age while blood alanine concentrations delined. Serum insulin and blood alanine concentrations were also related to weight. No marked sex-related differences were found, although blood glycerol concentration was slightly higher in women. Distribution of all metabolite concentrations was positively skewed, except for glucose, but skewness could be corrected by logarithmic transformation. Skew was particularly marked for blood ketone body concentrations. Concentrations of all metabolites in plasma exceeded those in whole blood, but this was significant for only lactate and pyruvate when concentrations in plasma were compared with calculated concentrations in erythrocyte water.