A 35-year-old woman presented to the emergency department with a 2 days history of malaise and headache. She was breastfeeding her 5-month old infant and had recently started an altered diet based on reducing carbohydrate amount. Moreover, she had also started exercising 2 weeks prior to her illness. Initial blood tests revealed high anion gap metabolic acidosis and hypoglycaemia (pH 7.13 (normal 7.30-7.40), bicarbonate 9.4 mmol/L (normal 21.0-28.0), anion gap 22.6 mmol/L (normal 8-12), glucose 2.9 mmol/L (normal fasting 3.9-5.8) and ketones 6.4 mmol/L (normal <0.6)). The patient was treated with intravenous dextrose and showed complete resolution of ketoacidosis and hypoglycaemia within 48 hours. She was discharged home and remained well with a balanced diet. After excluding all other the causes of hypoglycaemia and ketoacidosis, the diagnosis of lactation ketoacidosis was made and it was considered triggered by altered diet, exercise and skipping meals. All 11 cases of lactation ketoacidosis which has previously been published are reviewed as well.