The present study investigated serum immunoglobulin (Ig) concentrations in relation to demographic factors, common habits (alcohol consumption and smoking) and metabolic abnormalities in an adult population-based survey including 460 individuals. Serum levels of interleukin (IL)-6, a marker of inflammation, were also determined. After adjusting for confounders, male sex was associated positively with IgA levels and negatively with IgM levels. Age was associated positively with IgA and IgG levels. Smoking was associated negatively with IgG levels. Heavy drinking was associated positively with IgA levels. Metabolic abnormalities (obesity and metabolic syndrome) were associated positively with IgA levels. Abdominal obesity and hypertriglyceridaemia were the components of metabolic syndrome associated most strongly with serum IgA. Heavy drinkers with metabolic syndrome showed particularly high serum IgA levels. Serum IL-6 levels were correlated positively with IgA and IgG concentrations. It is concluded that sex, age, alcohol consumption, smoking and common metabolic abnormalities should be taken into account when interpreting serum levels of IgA, IgG and IgM.