An experiment work was carried out to investigate the effects of oral administration of nonsteroidal antiinflammatory drugs (NSAIDs) on blood glucose level and haematological parameters (TEC, TLC, Hb%, DLC) in mice. Out of three groups of mice (each containing 10 mice), one group was kept as control without giving any drug. Another two groups of mice received separately aspirin (Ecospirin®, 620 mg/kg b.wt.) and paracetamol (Napa®, 333 mg/kg b.wt.) orally along with normal feed. In treated groups, the blood glucose level and total leucocyte count were increased significantly (p<0.01) but the total erythrocyte count (TEC) and haemoglobin content (Hb%) were decreased significantly (p<0.01). In case of differential leukocyte count (DLC), neutrophil count was decreased significantly (p<0.01) but lymphocyte count was increased significantly (p<0.01) in treated groups. In post-mortem examination, congested and hyalinized liver, enlarged kidney and spleen, hemorrhagic stomach and ulcerated intestine were found in NSAIDs treated mice. Long-term oral administration of NSAID is not recommended due to side effects.