Introduction: Fasting is a duty for Moslems. They must avoid eating & drinking from dawn to dusk. In order to determine fasting effects on health, measuring BLOOD biochemical PARAMETERS in normal adult males performed this study Material & Methods: In this experimented study we compared the results of BLOOD biochemical tests (FBS, TG, Ch, Uric acid, Na, K, Ca, P, AST, ALT, ALP, LDH) before, during & after Ramadan fasting in 100 normal males in Kashanian in 1995. Before Ramadan, after 12 hours fasting, 10cc BLOOD was taken and serum was separated. Na & K were measured by flame photometer & other factors by RA-1000 Autoanalizer with kits of Man Company (Control group) At the end of first, second, third & forth weeks of Ramadan, samples was collected and measurement was done (cases group) Multi Parameter ANOYA & T-paired test was carried out. Results: After the completion of the study, the following results were observed by comparing the subjects BLOOD PARAMETERS before and at the end of Ramadan: 1. Ch, Cr, K, Ca, P, AST, ALT, showed no significant differences. 2. FBS, Uric acid (P<0.003), TG, Na (P<0.0001), BUN (P<0.012), ALP (P<0.005) showed significant decrease. 3. LDH had significantly increased. (P<0.002) All of results were in normal limits.Conclusion: Considering this result, fasting had no effect on Ch, Cr. K, Ca. P, AST, ALT metabolism, but increased metabolism of glucose, Uric acid, TG, NA, ALP. Normal kidney function was preserved. Liver enzymes showed no changes ALP & LDH level changes were within physrologic limits. fasting had no side effect of human health.