The risk of ketogenic diets while breastfeeding: severe euglycaemic ketoacidosis

A 31‐year‐old Caucasian woman presented to the emergency department with a 1‐day history of vomiting and lethargy, but no other symptoms. Her medical history included a normal vaginal delivery 9 weeks before, appendicectomy in 2011, and pyelonephritis in 2010. Her pregnancy was uncomplicated, and she exclusively breastfed her baby every 3 hours. She was not taking any medications. Four days before presentation, she commenced a ketogenic diet and was fasting each day until midday, losing 2.5 kg during these 4 days, having had a normal diet previously. She reported an intake of 7530 kJ per day and was walking for 30 minutes daily. Her diet consisted of animal protein and low carbohydrate vegetables, with the aim of reducing carbohydrate intake below 50 g daily. There was no personal or family history of diabetes, and no recent alcohol or recreational substance use. On examination, she was afebrile and haemodynamically stable with blood pressure of 121/80 mmHg, a heart rate of 116 beats per minute, a respiratory rate of 20 breaths per minute, and oxygen saturation of 99% on room air. Her body mass index was in the mildly overweight range at 26 (normal range, 18.5–24.9). Investigations showed high anion gap acidosis (28 mmol/L; reference interval [RI], 12–20 mmol/L) with a baseline venous pH of 7.08 (RI, 7.30–7.40), a bicarbonate level of 6 mmol/L (RI, 22–32 mmol/L), arterial blood gas base excess of − 24 mmol/L (RI, − 3–3 mmol/L), high levels of serum ketones (7 mmol/L; RI, < 0.8 mmol/L), and normal levels of lactate (0.7 mmol/L; RI, ≤ 2.0 mmol/L) and blood glucose (4.2 mmol/L; RI, 3.5–7.7 mmol/L). Her serum potassium level was 4.2 mmol/L (RI, 3.2–5.0 mmol/L), her creatinine level was 69 µmol/L (RI, 45–90 µmol/L) and estimated glomerular filtration rate was > 90mL/min/1.73m². Urinalysis did not suggest underlying infection. She was managed with intravenous thiamine, 5% dextrose, Hartmann’s solution and potassium supplementation during an overnight admission, in addition to encouraging oral intake of simple carbohydrates such as apple juice. The following morning a venous blood gas sample showed resolution of ketoacidosis, with a pH of 7.36, and levels of bicarbonate (25 mmol/L), ketones (0.2 mmol/L) and blood glucose (6.7 mmol/L) within normal range. She felt well and was discharged home that day, with advice to increase carbohydrate intake, particularly while breastfeeding. At outpatient follow‐up, she was progressing well in the community and maintaining a higher carbohydrate intake while breastfeeding.