Aims: Diabetes mellitus is associated by increased blood glucose level resulting from lack of Insulin or Insulin resistance in peripheral tissues or both. The aim of this study was to investigate the effects of Nigella sativa L. seed hydroalcoholic extract on blood biochemical parameters in STZ-induced diabetic rats.

  Materials & Methods: This interventional study was done on 60 male Wistar rats. Animals were randomly divided into 6 groups (n=10) including control, diabetic (receiving saline), groups receiving 100, 200 and 400mg/kg doses of the extract and positive control (receiving 300mg/kg Metformin). Animals were treated for 6 weeks with gavage from start (zero), 24 and 45 days of the study. Glucose, cholesterol, triglycerides, HDL and LDL were measured after 12hours of fasting. Data were analyzed by SPSS 16 software and One-way ANOVA, Tukey and Paired-T tests.

  Findings: Blood sugar levels in diabetic rats receiving 200mg/kg dose of the extract was reduced more significantly than other treated groups (p<0.01). There was a significant difference in cholesterol and triglyceride at day 45 in all treated groups compared to diabetic group (p<0.001). No significant difference was observed in HDL in groups. A significant reduction in LDL was observed in diabetic group treated with Metformin and Nigella extract at day 45.

  Conclusion: Nigella sativa L. extract reduces glucose, cholesterol, triglyceride, and LDL levels in diabetic rats.