Hyperosmolar Hyperglycaemic State
Summary
Hyperosmolar hyperglycaemic state (HHS) is a life-threatening diabetic emergency characterised by severe hyperglycaemia (typically greater than 30mmol/L), hyperosmolality (greater than 320 mOsm/kg), and profound dehydration without significant ketoacidosis. It typically occurs in elderly patients with type 2 diabetes, often precipitated by infection, poor compliance, or new diabetes. HHS develops more gradually than DKA (often over days) and carries a higher mortality (15-20%). Treatment involves slow, cautious fluid replacement, low-dose insulin, and identification and treatment of the precipitant.
Key Facts
- Definition: Severe hyperglycaemia + hyperosmolality without significant ketonaemia
- Incidence: Less common than DKA but higher mortality
- Peak Demographics: Elderly patients with T2DM
- Pathognomonic: Glucose greater than 30mmol/L + osmolality greater than 320 + minimal ketones
- Gold Standard Investigation: Venous glucose, serum osmolality, ketones, U and E
- First-line Treatment: Cautious 0.9% saline, low-dose insulin
- Prognosis: 15-20% mortality
Clinical Pearls
Fluid Pearl: Replace fluids MORE SLOWLY than in DKA - risk of cerebral oedema with rapid correction.
Insulin Pearl: Lower dose insulin (0.05 units/kg/hr) - the primary issue is dehydration not ketosis.
Thrombosis Pearl: High VTE risk - consider prophylactic anticoagulation.
| Feature | HHS | DKA (comparison) |
|---|---|---|
| Glucose | Greater than 30mmol/L | Usually greater than 11 |
| Osmolality | Greater than 320 | Variable |
| Ketones | Minimal (less than 3) | Greater than 3 |
| pH | Greater than 7.3 | Less than 7.3 |
| Bicarbonate | Greater than 15 | Less than 15 |
- Infection (most common)
- MI/stroke
- Poor compliance
- New diabetes
- Medications (steroids, thiazides)
Algorithm
Fluid Replacement
| Phase | Protocol |
|---|---|
| First 6h | 0.9% saline (slower than DKA) |
| Ongoing | Replace deficit over 48 hours |
| Targets | Glucose fall 5mmol/L/hr; osmolality fall 3-8 mOsm/hr |
Insulin
| Regimen | Dose |
|---|---|
| Fixed rate IV | 0.05 units/kg/hr (lower than DKA) |
| Start | After fluids commenced |
Potassium
- Replace as needed (monitor closely)
VTE Prophylaxis
- LMWH unless contraindicated
-
Joint British Diabetes Societies. Management of Hyperosmolar Hyperglycaemic State (HHS) in Adults. 2022. JBDS Guidelines
-
Pasquel FJ, Umpierrez GE. Hyperosmolar Hyperglycemic State. Nat Rev Dis Primers. 2017;3:17042. PMID: 28644378
Viva Points
"HHS: elderly T2DM, glucose greater than 30, osmolality greater than 320, minimal ketones. Different from DKA - not acidotic. Treat with SLOW fluids, low-dose insulin. Higher mortality than DKA (15-20%). VTE prophylaxis essential."
Last Reviewed: 2026-01-01 | MedVellum Editorial Team