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Diabetic ketoacidosis (DKA) and the hyperosmolar hyperglycaemic state (HHS)
In both crises treatment rests on three pillars in the same order — fluids, potassium and insulin — and insulin is not started before potassium is 3.5 mmol/L or more.
Why it matters in the exam
This is a standard emergency topic. A typical question presents a young person with type 1 diabetes, vomiting, abdominal pain, Kussmaul breathing and a smell of acetone, or an older person with type 2 diabetes who has been getting dehydrated for days and arrives confused with glucose above 600 mg/dL. The candidate must identify the crisis from the criteria: in DKA — glucose 200 mg/dL or more (or known diabetes), ketones (beta-hydroxybutyrate 3.0 mmol/L or more) and acidosis (pH below 7.3 or bicarbonate below 18); in HHS — glucose 600 mg/dL or more, high osmolality and no significant acidosis.
Then comes the question "what is the first step": isotonic fluids (about 500–1000 mL per hour for the first 2–4 hours), a potassium check before insulin, and an insulin infusion of 0.1 units per kg per hour. Well-known distractors: bicarbonate (given only when pH is below 7.0), stopping the insulin infusion when the glucose falls (instead dextrose is added at 250 mg/dL and insulin continues until the acidosis closes), and stopping the infusion without overlap with subcutaneous insulin. Euglycaemic ketoacidosis in patients on SGLT2 inhibitors must also be remembered, and cerebral oedema — mainly in children — from overly rapid correction.
Key points
- DKA: glucose 200 mg/dL or more, ketones 3.0 mmol/L or more, pH below 7.3 or HCO3 below 18.
- HHS: glucose 600 mg/dL or more, osmolality above 300, no significant acidosis.
- Order: fluids, potassium, insulin 0.1 units/kg/h.
- Potassium below 3.5 → potassium before insulin; dextrose when glucose is below 250 mg/dL.
- Bicarbonate only when pH is below 7.0; overlap with basal insulin 1–2 hours before stopping the infusion.
Summary table
| Parameter | DKA | HHS | Note |
|---|---|---|---|
| Glucose | 200 mg/dL or more (or known diabetes) | 600 mg/dL or more | On an SGLT2 inhibitor glucose may be near normal |
| Acid-base | pH below 7.3 or HCO3 below 18 | pH 7.3 or more, HCO3 15 or more | DKA: high anion gap |
| Ketones | Beta-hydroxybutyrate 3.0 mmol/L or more | Below 3.0 | Measure in blood, not only in urine |
| Osmolality | Variable | Effective above 300 mOsm/kg | HHS: confusion and coma |
| Fluids | Isotonic 500–1000 mL per hour for the first 2–4 hours | As in DKA, with care in older patients | Dextrose 5% when glucose is below 250 mg/dL |
| Potassium and insulin | Below 3.5: potassium first; 3.5–5.0: add to fluids | Insulin 0.1 units/kg/h | Bicarbonate only when pH is below 7.0 |
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Sources
- Hyperglycemic Crises in Adults With Diabetes: A Consensus Report (ADA, EASD, JBDS, AACE, DTS), 2024 — Diagnostic criteria and management of DKA and HHS
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Diabetes Mellitus: Complications — Acute complications
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.
See also: in children: Diabetic ketoacidosis in children