Introduction: Ketoacidosis is commonly occurred in uncontrolled diabetes mellitus patients. However, severe metabolic acidosis due to starvation is rarely reported in literature. We describe a case of ketoacidosis in a 27-year old pregnant female at week 30 of gestation, with normal former pregnancy.She was admitted to hospital with a 24-hour history of vomiting (more than 30 times in a day). There was no additional pain or symptoms.Case Report: On admission, she was normotensive.Blood glucose was 111 mg/dL, serum creatinine0.6 mg/dL, and urine dipstick showed acetone (3+) without Proteinuria. Urine pH was 6. Blood gas analysis showed severe metabolic acidosis with a PH of 7.24 (HCO3- 7.9 meq/L, BE -14, PCO2 15.2 mmHg, PO2 72 mmHg). Then, we checked serum electrolytes. Serum chloride was 102 mg/ dL, Na=135 meq/L, K=5 meq/L. Based on these data, there was high anion gap metabolic acidosis in patient. After 3 days hydration with dextrose in saline, gradually blood gas improved as on discharge it showed pH 7.44, PCO2=44 mmHg, HCO3-=28 meq/L, and her vomiting had been disappeared.Conclusions: We conclude that in this case acidosis was due to starvation and inhibition of insulin secretion that led to ketone production. After correction of dehydration by glucose replacement, she was improved and discharged.