Clinical reasoning notes. Fluid, insulin and potassium regimens differ between hospitals: follow your local protocol and monitor closely.
The reasoning chain: recognise the emergency → confirm the three diagnostic features → find the trigger → correct fluid first, then insulin, with potassium watched at every step → monitor for complications → prevent the next episode.
1. Definition: three things must be present
Diabetic ketoacidosis (DKA) needs all three:
- Hyperglycaemia: blood glucose above about 11 mmol/L (200 mg/dL), or known diabetes (it can be lower in "euglycaemic" DKA, which is seen with SGLT2 inhibitors and in pregnancy).
- Ketosis: blood ketones 3 mmol/L or more, or 2+ or more on urine dipstick.
- Acidosis: pH below 7.3 or bicarbonate below 15 mmol/L.
Severity (by pH): mild 7.25 to 7.30, moderate 7.00 to 7.24, severe below 7.00, together with drowsiness or coma.
Hyperosmolar hyperglycaemic state (HHS) is the other emergency: very high glucose (above about 30 mmol/L), little or no ketosis, severe dehydration and high osmolality, usually in older type 2 patients, with a gradual onset over days.
2. Why it happens
Without insulin the body cannot use glucose, so it breaks down fat into ketone acids (acetoacetate, β-hydroxybutyrate). The glucose spills into the urine and pulls water and electrolytes with it (osmotic diuresis), so the patient is dry and short of potassium, even if the blood potassium looks normal or high.
3. Find the trigger (the "I"s)
- Infection (the commonest: pneumonia, urinary infection, sepsis, malaria, TB, HIV)
- Insulin missed or stopped (including running out, or a faulty pen)
- Infarction (a silent heart attack), Injury or surgery, Intercurrent illness such as pancreatitis, stroke
- Initial presentation of type 1 diabetes (a child with weight loss, thirst and breathing fast)
- Increased insulin needs: pregnancy, steroids
- Iatrogenic drugs: steroids, thiazides, antipsychotics, SGLT2 inhibitors
4. Presentation
Polyuria, polydipsia, weight loss, nausea, vomiting and abdominal pain (can mimic an acute abdomen), deep sighing "Kussmaul" breathing, a fruity (acetone) smell, dehydration, tachycardia, low blood pressure, drowsiness or coma.
5. Investigate with purpose
| Test | The question it answers |
|---|---|
| Capillary glucose and blood or urine ketones | Is it DKA? Quick to do at the bedside |
| Blood gas (arterial or venous) | How acidotic? pH and bicarbonate stage the severity |
| Urea, creatinine, electrolytes | Kidney function; potassium decides the insulin plan; sodium (correct it for the glucose) |
| Anion gap | A raised gap confirms a ketoacid cause: gap = Na − (Cl + HCO₃) |
| Full haemogram, CRP, blood cultures, urine culture, malaria test, chest X-ray | Is there infection as the trigger? |
| ECG | Is there a silent infarct? What do the potassium changes look like? |
| HbA1c | How long has glucose been high? New diabetes or poorly controlled? |
| Serum amylase or lipase | Pancreatitis can cause DKA, and DKA can raise amylase |
Where results can mislead: the serum potassium can be normal or high at presentation although the body is very short of potassium (acidosis moves potassium out of the cells). It falls fast once insulin starts. The measured sodium is falsely low with very high glucose. The abdominal pain of DKA often settles once treated: do not rush to surgery.
6. Management: fluid first, then insulin, watch potassium
- Fluids: rapid isotonic saline to restore circulation, then continue to correct the deficit over 24 to 48 hours. This alone lowers glucose and starts to clear ketones.
- Potassium (before insulin): if potassium is below 3.3 mmol/L, replace it and delay insulin (insulin can drive potassium dangerously low and cause arrhythmias). If it is above 5.3 mmol/L, give no potassium and recheck. In between, add potassium to the fluids.
- Insulin: a fixed-rate IV insulin infusion until ketones clear and the acidosis resolves. When glucose falls below about 14 mmol/L, add dextrose to the fluids and continue insulin until ketosis has cleared. Do not stop insulin because the glucose looks normal.
- Treat the trigger: antibiotics for infection, antimalarials for malaria, and so on.
- Bicarbonate is generally not given, except in very severe acidosis with shock.
- Monitor: glucose hourly, ketones and gas every 2 hours, potassium regularly, urine output, mental state.
7. Complications to watch for
Hypokalaemia and hypoglycaemia from treatment, cerebral oedema (mainly in children, with headache, a falling level of consciousness and bradycardia: reduce the rate of fluids and give mannitol), pulmonary oedema from too much fluid, thromboembolism, aspiration, sepsis, acute kidney injury.
8. Before discharge
Restart subcutaneous insulin and overlap it with the infusion for at least 30 to 60 minutes. Educate on sick-day rules (never stop insulin, check ketones, drink fluids, seek help early), injection technique and access to insulin and supplies.
Examiner questions
- State the three criteria for DKA.
- Why can the serum potassium be high when the body is potassium-depleted, and what happens once insulin starts?
- Why do we give fluids before insulin, and why do we add dextrose when the glucose falls?
Practice questions
1. A 19-year-old is drowsy with deep rapid breathing, glucose 28 mmol/L, ketones 5 mmol/L and pH 7.1. The first priority is: A. Insulin bolus · B. Rapid IV isotonic saline · C. Sodium bicarbonate · D. Oral fluids · E. Subcutaneous insulin Answer: B. Fluids come first, then insulin once the potassium is known.
2. The potassium is 2.9 mmol/L before treatment. The correct step is: A. Start insulin at once · B. Replace potassium and delay insulin · C. Give bicarbonate · D. Stop fluids · E. Give no potassium Answer: B. Insulin would drive the potassium lower and risk arrhythmia.
3. Which feature best separates HHS from DKA? A. Dehydration · B. Very high glucose with little or no ketosis · C. Infection as a trigger · D. Altered consciousness · E. Hypokalaemia Answer: B.
4. The most feared complication of DKA treatment in children is: A. Hyperkalaemia · B. Hypernatraemia · C. Cerebral oedema · D. Pancreatitis · E. Optic neuritis Answer: C.