Diabetic Ketoacidosis
A medical emergency in which absolute or severe relative insulin deficiency unleashes unopposed lipolysis and ketogenesis alongside unrestrained hyperglycaemia, producing a life-threatening triad of hyperglycaemia, ketonaemia and acidosis that fluids, insulin and potassium replacement are designed to reverse in that order.
In a nutshell
Insulin deficiency permits both unrestrained hyperglycaemia and unopposed ketogenesis, producing an acidosis that drives Kussmaul breathing, vomiting and dehydration. Fluids come first, then insulin to switch off ketogenesis, with potassium replaced proactively because insulin drives it into cells on top of existing depletion.
Classic presentation
A known type 1 diabetic (or new presentation) with polyuria, vomiting, abdominal pain, Kussmaul breathing and acetone breath, often precipitated by infection or missed insulin.
Key points
- The diagnostic triad is hyperglycaemia, ketonaemia (or ketonuria) and acidosis: all three should be sought together.
- Serum potassium can be normal or high at presentation despite severe total-body depletion, because acidosis and insulin deficiency shift potassium out of cells.
- Insulin's essential job in DKA is switching off ketogenesis, not just lowering glucose: fluids alone lower glucose but do not stop ketone production.
- Fluids are given before insulin because correcting the profound fluid deficit takes priority and begins improving glucose independently.
- Euglycaemic DKA can occur, particularly with SGLT2 inhibitor use, so a normal glucose does not exclude the diagnosis if ketones and acidosis are present.
- Cerebral oedema is a feared complication of overly rapid correction, particularly in children and young adults.
First-line investigation
Blood glucose, blood ketones and a venous blood gas together, to confirm the diagnostic triad of hyperglycaemia, ketonaemia and acidosis.
First-line management
Intravenous 0.9% sodium chloride to correct dehydration first, followed by a fixed-rate intravenous insulin infusion, with proactive potassium replacement.
Exam traps
- Do not start insulin before fluids: the sequence in exam stems matters and fluids come first.
- A normal or high potassium on the first blood test does not mean potassium is safe; anticipate the fall once insulin starts.
- A normal glucose does not exclude DKA: check ketones and pH, especially in patients on SGLT2 inhibitors.
- Abdominal pain and vomiting in DKA can mimic a surgical abdomen; treat the metabolic derangement and reassess rather than rushing to surgery.
Educational content pending clinical review. Not medical advice.