FFinalistSouthampton · 2027
Acute care
AKT · Acute care/Metabolic & endocrine

Hyperosmolar hyperglycaemic state (HHS)

Severe hyperglycaemia + hyperosmolality without significant ketosis

Overview

A type 2 diabetes emergency of profound hyperglycaemia, hyperosmolality and severe dehydration WITHOUT significant ketoacidosis (residual insulin suppresses ketogenesis). Onset is slower than DKA; fluid replacement is the mainstay and insulin is used cautiously.

Recognise

  • Marked hyperglycaemia (often >30), severe dehydration, hypovolaemia
  • Reduced consciousness/confusion; osmolality typically >320
  • Minimal ketones/acidosis (unlike DKA); high VTE risk

Red flags

  • Profound dehydration/hypovolaemic shock, reduced GCS, very high osmolality; high thrombosis risk

Differentials & how to tell them apart

Diabetic ketoacidosis (DKA)younger/type 1, ketonaemia + acidosis, faster onset
Sepsisinfective source — often the precipitant of HHS
Stroke/other cause of reduced GCSimaging if focal signs; HHS itself depresses consciousness

Investigations

Glucose, osmolality (or calculated), U&E, ketones (low), venous gas, FBC/CRP, search for precipitant (infection, MI).

Management

IV 0.9% saline (cautious rehydration) first; low-dose insulin only if needed; VTE prophylaxis

  1. 1Cautious IV 0.9% saline rehydration (the priority); glucose often falls with fluids alone. Give VTE prophylaxis.Gate: Start insulin only once glucose stops falling with fluids (or if significant ketones) — early/aggressive insulin risks dangerous osmotic shifts
  2. 2Correct electrolytes gradually; treat the precipitant; aim for a slow correction of osmolality/glucose.
IV 0.9% sodium chloride — cautious fluid replacement is the mainstay (slower than DKA)
Low-dose IV insulin — only once glucose stops falling with fluids alone, or if ketonaemia present
LMWH prophylaxis — high VTE risk

Key points

Slower, gentler than DKA: fluids first and insulin later/lower. Rapid osmotic shifts risk cerebral oedema and central pontine myelinolysis. VTE risk is high.

Monitor & prognosis

Glucose, osmolality, U&E, fluid balance, GCS — aim for gradual correction.

Higher mortality than DKA (older, comorbid); good if corrected slowly.

Source: JBDS-IP (HHS guideline)