skip to main content

Hyperosmolar Hyperglycaemic State — RACP Adult Medicine MCQ

Instant feedback + full explanation. One question, done properly.

EasyEndocrinologyHyperosmolar Hyperglycaemic StateRACP Adult Medicine

A 70-year-old man with T2DM presents with progressive drowsiness over 5 days. He has polyuria, polydipsia, and confusion. Blood glucose is 55 mmol/L. Serum osmolality is 380 mOsm/kg. pH is 7.35 (no significant acidosis). Ketones are 0.5 mmol/L (trace). Na⁺ is 155 mmol/L. He is profoundly dehydrated. What is the most likely diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — HHS

Very high glucose (>30 mmol/L), hyperosmolality (>320 mOsm/kg), severe dehydration, altered consciousness, minimal ketonaemia, and no significant acidosis is HHS (hyperosmolar hyperglycaemic state). HHS has higher mortality than DKA (~15-20% vs ~1%). Treatment: aggressive IV 0.9% NaCl (fluid deficit often 8-12 L), LOW-dose IV insulin (0.05 units/kg/hr — avoid rapid glucose/osmolality correction which causes cerebral oedema), DVT prophylaxis, and slow Na⁺ correction.

Reference: ADS – 2024 – HHS Protocol; JBDS-IP 2024