Diabetic ketoacidosis results from insulin deficiency and insulin resistance and is marked by hyperglycaemia, ketoacidosis, dehydration and electrolyte losses. Management includes correction of shock, dehydration, electrolyte deficits, hyperglycaemia, acidosis and sepsis (if present). Warning signs include severe dehydration, shock, pH < 7.0, hypokalaemia, hypernatraemia, hyperosmolality, hyperlipidaemia, deterioration in consciousness and diabetic ketoacidosis in very young patients. The principles of treatment include (i) admission to a unit with paediatric experience, (ii) treatment of shock, (iii) rehydration over 24-36 h, or longer if the osmolality is >360 mmoll(-1), (iv) normal saline for rehydration unless the patient is hypernatraemic, (v) avoidance of bicarbonate unless acidosis is interfering with myocardial contractility, (vi) insulin infusion to achieve a fall in blood glucose levels of 5 mmol h(-1), (vi) potassium, (vii) use of 5% glucose when the blood glucose level falls <12mmoll(-1), (ix) treatment of any complications and (x) change to subcutaneous insulin when diabetic ketoacidosis is controlled.