The basic aim of this placebo control study was to investigate the effects of three different preparations of Nigella sativa especially on glucose and lipid metabolism in type 2 diabetes mellitus (DM2) patients (group-A); however normal individuals (group- B) was also studied. Both groups were treated with N. sativa Seed Powder (NsP), N. sativa Aqueous Extract (NsE) and N. sativa Oil (NsO), in addition to a placebo in phases 1, 2 and 3 respectively. Each phase was of 80 days (40 days of treatment with N. sativa preparation followed by 40 days of placebo administration). Levels of 0 day were taken as base line (concurrent control) in each phase. Fasting blood levels of glucose, insulin, total cholesterol (TC), LDL & HDL cholesterols, triglycerides (TG), total leukocyte & platelet counts, hepatic profile and blood urea were determined in subjects of both groups on 0, 40 and 80 th day of each phase of the study. In phase-1 a highly significant fall in fasting blood glucose, TC, LDL cholesterol and TG while an increase in insulin and HDL was observed in group-A after treatment with NsP as compared to concurrent control. These levels significantly reversed at the end of placebo except the HDL cholesterol. Almost similar results were obtained in subjects of group-B. In phase-2 although a decrease in glucose and increase in insulin levels was observed in group-A after treatment with NsE; which reversed after the placebo yet the changes were not significant. However a significant fall was observed in TC and TG levels of diabetics after NsE treatment; which reversed after the placebo significantly in TG but insignificantly in TC. In group B, results regarding glucose and insulin levels were similar to that of group-A of this phase. Concerning lipid profile, a significant fall in TG and insignificant decrease in TC and LDL cholesterol was observed after NsE treatment. The changes reversed after the placebo, significantly in TG and LDL cholesterol but insignificantly in TC. In phase-3, a significant fall in fasting blood glucose and a rise in insulin levels was observed in group-A after treatment with NsO2 as compared to concurrent control levels. A significant decrease in LDL & increase in HDL was observed while TC remained statistically unchanged; however a significant increase was also recorded in TG after NsO treatment. LDL and TG levels reversed significantly, while no significant change was observed in HDL and TC levels after the placebo. Subjects of group-B behaved similar to group-A, as for glucose and insulin are concerned. Regarding lipids, a decrease in LDL cholesterol (significant) and TC (insignificant) while increase in HDL cholesterol and TG (insignificant) was observed in group-B after the use of NsO. LDL and TC increased significantly after the placebo while no significant change was recorded in HDL cholesterol and TG. Total leukocyte and platelet counts remained statistically unchanged in both groups A and B, when treated with NsP, NsE, NsO or administered with placeboes in phases 1, 2 and 3 respectively as compared to their base line levels Similarly no unpleasant effect of any of the N. sativa preparation was observed regarding hepatic profile, blood urea and the subjective feelings of the diabetic and normal individuals. In the light of foregoing facts it can safely be concluded that all preparations of N. sativa had some or more antidiabetic effect. However keeping in view the overall performance, NsP was found more effective. Further large scale human studies with different dose schedules of NsP are recommended.