Lithium is commonly used in treating mental disorders and bipolar diseases. As physicians frequently keep the patients on long-term lithium therapy, awareness of the numerous side effects and pathogenesis of this lightest alkali metal is needed for such treatments. The present study was designed to evaluate the toxic effect of small doses of lithium chloride in male Wistar rats. The oral administration of lithium chloride (15, 30 mg/kg body wt) for 7 weeks through their drinking water elicited a significant alteration in their body weight and blood serum chemistry. The serum enzyme levels of alkaline phosphatase (ALP), high density lipoprotein (HDLP), and creatinine kinase (CK) were diminished, whereas the level of serum urea and glucose were elevated in the lithium treated animals, depicting the disturbed general physiological status. Furthermore, a marked inhibition in the levels of serum alanine and aspartate transaminases (ALT and AST) reflected a stimulating transamination reaction in hepatic and renal tissues. Lithium exposure also reduced the glutathione (GSH) level and stimulated the lipid peroxidation (LPO) level in the rat blood cells, indicating oxidative stress in the red blood cells due to lithium exposures. The histopathological observations of the liver and kidney tissues revealed many deformities and histological alterations due to lithium treatment. The results of present study suggest that small doses of lithium induce toxicity in rat blood as well as in liver and kidney tissues. However, the precise mechanism of lithium toxicity is still incompletely understood.