This experiment was conducted to study the effects of some medicinal plants on bone formation and bone resorption in normal and diabetic rats. The studies included two experiments; the first was in summer while the second was in winter season. Each experiment included 120 adult male albino rats averaged 100±10 gm live body weight. Normal rats were distributed into 4 groups (15 rats each). Group1 fed control diet, Group2 fed garlic 5%, Group3 fed Nigella sativa 5%, Group4 fed garlic 2.5% + Nigella sativa 2.5 %, while four groups included diabetic rats, Group5 (Control), Group6 fed garlic 5 %, Group7 fed Nigella sativa 5% and Group8 fed garlic 2.5% + Nigella sativa 2.5%. Blood samples were collected after 4 and 8 weeks from the start of the experiment and centrifuged at 3000 rpm for 15 minutes to obtain serum. Results show that serum lactic dehydrogenase, alkaline phosphatases, glucose and parathyroid hormone were significantly increased in diabetic rats than normal rats while treatment of diabetic rats with medicinal plants efficiently modify this effect. Serum osteocalcin was significantly decreased in diabetic rats than normal rats. Conclusion, treatment with medicinal plant has a beneficial effect on regulating bone formation and resorption either in normal or diabetic rats.