Aims Skeletal muscle is a major metabolic organ and plays important roles in glucose metabolism, insulin sensitivity and insulin action. Muscle telomere length reflects the myocyte's exposure to harmful environmental factors. Leukocyte telomere length is considered a marker of muscle telomere length and is used in epidemiologic studies to assess associations with ageing-related diseases where muscle physiology is important. However, the extent to which leucocyte and muscle telomere length are correlated is unknown, as are their relative correlations with glucose and insulin concentrations. The purpose of this study was to determine the extent of these relationships. Methods Leucocyte and muscle telomere length were measured by quantitative real-time polymerase chain reaction in participants from the Malmö Exercise Intervention (n=27) and the Prevalence, Prediction and Prevention of Diabetes-Botnia studies (n=31). Participants in both studies were free from Type2 diabetes. We assessed the association between leucocyte telomere length, muscle telomere length and metabolic traits using Spearmen correlations and multivariate linear regression. Bland-Altman analysis was used to assess agreement between leucocyte and muscle telomere length. Results In age-, study-, diabetes family history- and sex-adjusted models, leucocyte and muscle telomere length were positively correlated (r=0.39, 95%CI 0.15-0.59). Leucocyte telomere length was inversely associated with 2-h glucose concentrations (r=-0.58, 95%CI -1.0 to -0.16), but there was no correlation between muscle telomere length and 2-h glucose concentrations (r=0.05, 95%CI -0.35 to 0.46) or between leucocyte or muscle telomere length with other metabolic traits. Conclusions In summary, the current study supports the use of leucocyte telomere length as a proxy for muscle telomere length in epidemiological studies of Type2 diabetes aetiology.