Summary. Studies from tertiary care medical centres have linked hepatitis C virus (HCV) to the development of insulin resistance (IR) and type 2 diabetes. The aim of the study is to assess the relationship between HCV positivity and insulin resistance/diabetes in the US population. Three cycles of the National Health and Nutrition Examination Survey (NHANES) conducted between 1988 and 2008 were used. HCV infection was diagnosed using a positive serologic anti-HCV test. Additionally, diabetes was diagnosed as fasting blood glucose ≥126 mg/dL and/or the use of hypoglycaemic medications. Insulin resistance was defined as a homeostasis of model assessment (HOMA) score of >3.0. Logistic regression was used to estimate the odds ratios (ORs) of each of the potential risk factors for diabetes mellitus (DM). The SUDAAN 10.0 was used to run descriptive and regression analyses. A total of 39 506 individuals from three NHANES cycles (1988–1994, 1999–2004 and 2005–2008) with complete demographic and relevant clinical data were included. Over these three NHANES cycles, prevalence of hepatitis C did not significantly change. During the first NHANES cycle (1988–1994), insulin and diabetes were independently associated with hepatitis C. However, during the later study cycles (1998–2008), these associations were no longer significant. In contrast, other important known risk factors for diabetes and IR (male gender, non-Caucasian race, age and obesity) remained significant over all three NHANES cycles. Although HCV infection was independently associated with an increased risk of diabetes and IR in the US population over a decade ago, assessment of the later NHANES cycles shows that this relationship may have become diluted by the rapid rise of other risks for diabetes, specifically, the prevalence of obesity.