Endocrine and metabolic emergencies

Hyperosmolar hyperglycaemic state (HHS)

Reviewed Nov 2026·1 references
New· views rounded down, updated weekly

HHS = glucose ≥ 600 mg/dL, effective osmolality > 300 mOsm/kg, minimal ketosis and no significant acidosis. Rehydrate first and slowly; fall in osmolality 3-8 mOsm/kg/h and in Na+ ≤ 10 mmol/L/24 h; low-dose insulin 0.05 units/kg/h once glucose stops falling with fluid alone.

Definition
Glucose ≥ 600 mg/dL; calculated effective osmolality > 300 mOsm/kg (or total > 320); β-hydroxybutyrate < 3.0 mmol/L (urine ketones < 2+); pH ≥ 7.3 and HCO3- ≥ 15 mmol/L.

At the bedside

Timed steps
  1. 1

    Fluids

    0-4 h

    0.9% saline or balanced crystalloid 500-1000 mL/h for 2-4 h; deficit is ~100-220 mL/kg; correct over 24-48 h.

  2. 2

    Sodium may rise

    Watch

    A rising Na+ as glucose falls is expected (1.6 mmol/L per 100 mg/dL); switch to 0.45% saline only if osmolality is not falling despite positive balance.

  3. 3

    Low dose, later

    Insulin

    0.05 units/kg/h when glucose stops falling with fluids alone (or immediately if mixed DKA/HHS with BHB ≥ 3: 0.1 units/kg/h). Glucose fall ≤ 90-120 mg/dL/h.

  4. 4

    Rates

    Targets

    Osmolality fall 3-8 mOsm/kg/h; Na+ fall ≤ 10 mmol/L/24 h; keep glucose 200-300 mg/dL in the first 24 h.

  5. 5

    Complications

    Prevent

    Prophylactic LMWH (prothrombotic state), pressure care, look for infection, MI, stroke. Resolution: osmolality < 300, UO > 0.5 mL/kg/h, cognition improved, glucose < 250.

HHS without significant ketosis

Regular (soluble) insulin infusion

IV infusion
Dose
0.05 units/kg/h, started when glucose no longer falls with fluids
Worked example
80 kg: 4 units/h
Red flag · call your senior now
Seizures or worsening GCS during treatment: too-rapid osmolality fall; cerebral oedema or osmotic demyelination.
Pitfall
Treating HHS like DKA with high-dose insulin early, causing rapid osmotic shifts and circulatory collapse.
Pitfall
Starting hypotonic fluids because Na+ rises early.
Pearl
Calculate effective osmolality every 1-2 h at the start; plot glucose, Na+ and osmolality on a chart.

Calculators for this topic

Calculated serum osmolality (Indian units)

2 × Na + glucose (mg/dL)/18 + urea (mg/dL)/6. Uses blood urea, as reported by most Indian labs.

Sodium corrected for glucose

Na + 2.4 × (glucose − 100)/100 (Hillier; Katz uses 1.6).

References

  1. 1

    Umpierrez GE, Davis GM, ElSayed NA, et al. Hyperglycemic crises in adults with diabetes: a consensus report. Diabetes Care. 2024;47(8):1257-1275

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