The aim of this study was to investigate the prevalence of hyperinsulinaemia in a group of normozoospermic donors and the influence of insulin levels on in vitro fertilisation (IVF) outcome. Fasting insulin and 2 h post-eating insulin levels were determined for a group of thirty-four sperm donors. They were divided into three groups according to their insulin profiles. The association between insulin levels and embryo quality was determined in a clinical study for the different groups. The prevalence of raised insulin in the donor group was 44% with a 95% confidence interval of 27.2% and 62.1%. Donors with normal insulin levels produced more good quality blastocysts in the IVF programme
than those with abnormal insulin levels. These differences were not
statistically significant (P = 0.8638). Embryo quality in an IVF programme may be influenced by male insulin levels. The role of insulin in male fertility needs to be investigated.