Fish, Chrysichthys auratus were orally administered doses of garlic (Allium sativum) juice equivalent to 2g /kg b. wt. as a single dose or the same dose every 48h for 5 and 11 days. The fish were dissected 24 after the last dose. Serum glucose, total free amino acids (TFAA), total lipids, triglycerides, cholesterol, total protein, urea, AST, ALT and alkaline phosphatase (ALP) were determined. The levels of glycogen, total lipid, triglycerides and TFAA were measured in both liver and white muscle. Also, the liver and kidney were investigated histopathologically and histochemically. The results showed a hypoglycemia, hypolipidemia, hypocholesterolemia, hypotriglyceridemia and drop in serum TFAA as well as promotion of lipogenesis and glycogenesis in white muscle in response to repeated doses of garlic. Such results may correlate with the elevation of insulin release in the fish following the garlic administration. However, both histological and biochemical studies confirmed the liver glycogen depletion after garlic treatment. besides, histopathological changes in the liver after garlic treatment included vacuolation and hypertrophy and degeneration of some hepatocytes, dilatation and congestion of some blood vessels . The histopathological changes of the kidney in response to garlic administration were vacuolation and rupture of some renal tubules and degeneration of the parietal cells of some Malpighian corpuscles. Moreover, garlic decreased the amount of collagenous fibres in both liver and kidney as well as it reduced carbohydrate content in the kidney. In spite of some cell degeneration in the liver and renal tubules, the serum AST and ALT did not show any significant changes, while serum ALP was decreased. Generally, it could be concluded that garlic showed a high effect on the carbohydrate metabolism in Chrysichthys auratus. Also, garlic may improve the carbohydrate metabolism which probably, leads to lower the dietary protein costs of the fish. The damage effect of garlic on both liver and kidney may be attributed to the relative high dose of garlic used in this work.