Carbonic anhydrase is a pH regulatory enzyme, whose inhibition leads to metabolic acidosis. We investigated whether carbonic anhydrase inhibition may be associated with blood lactate accumulation in Streptozotocin (STZ) induced diabetic rats. The study aimed to provide a new marker to assist in identifying diabetic individuals at a high risk of developing lactic acidosis. Erythrocyte carbonic anhydrase activity with 4-nitrophenyl acetate as substrates was investigated in (STZ) induced diabetic rats. STZ induced diabetic rats showed significant increase in erythrocyte carbonic anhydrase (CA) activity of 9.7 ± 0.7 μMol/min/μL and blood lactate level of 6.2 ± 1.2 mMol/L when compared with Non Diabetic group CA enzyme activity of 5.5 ± 0.6 μMol/min/μL and blood lactate level of 3.9 ± 0.5 mMol/L. Inhibition of erythrocyte carbonic anhydrase activity with Acetazolamide results in 6.9 fold increase in blood lactate level when compared with Non diabetic group. Therefore inhibition of Carbonic anhydrase in STZ induced diabetic rats' result in blood lactate accumulation and reduced blood glucose concentration.