Diabetic ketoacidosis: a case-based approach to a diabetes emergency

The presentation

A 19-year-old with type 1 diabetes has been unwell with a flu-like illness for two days. He is now drowsy, breathing deeply and rapidly, very thirsty, passing large amounts of urine, and his breath has a sweet, fruity smell. He stopped some of his insulin because he "wasn't eating". Several classic features are present: the deep sighing breathing (Kussmaul breathing), dehydration from heavy urination, the ketone smell on the breath, and — crucially — an intercurrent illness plus reduced insulin, the commonest triggers.

Why DKA happens

Insulin is the signal that lets cells take in glucose for energy. Without enough of it — because of a missed dose, a new diagnosis, or the extra demand of an infection — cells "starve" despite high blood glucose. The body switches to burning fat, which produces ketones as a by-product. Ketones are acidic, so they build up and lower the blood's pH (metabolic acidosis). Meanwhile the very high glucose pulls water into the urine, causing heavy fluid and salt losses and dehydration. This combination — high glucose, high ketones and acidosis — defines DKA.

The tests that confirm it

DKA is confirmed by three findings together: raised blood glucose (usually high, though it can be only modestly elevated), significant ketones (measured in blood or urine), and acidosis on a blood gas (a low pH and low bicarbonate). Additional blood tests check kidney function and electrolytes — particularly potassium, which behaves in a dangerous way in DKA. A search for the trigger (often infection) runs in parallel. The diagnosis is usually clear quickly at the bedside with a glucose meter, ketone meter and blood gas.

Principles of treatment

Treatment follows established emergency protocols and rests on a few principles. First, replace fluids: people with DKA are markedly dehydrated and need intravenous fluids. Second, give insulin by infusion to switch off ketone production and let cells use glucose again. Third — and easily overlooked — manage potassium carefully: insulin drives potassium into cells, and levels that looked normal or high can fall dangerously, so potassium is monitored closely and replaced. Fourth, treat the underlying trigger. Throughout, glucose, ketones and blood chemistry are checked repeatedly, and the person is monitored for complications.

What the case teaches

The lessons are prevention and recognition. People with type 1 diabetes are taught "sick day rules" precisely because illness raises insulin needs — insulin should generally not be stopped even when not eating, and ketones should be checked. For clinicians, the pattern of deep breathing, dehydration, high glucose and ketones in someone with diabetes should trigger immediate assessment. DKA is a medical emergency, but with early recognition and protocol-driven treatment, the outlook is good.