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

Hypoglycaemia

Blood glucose <4 mmol/L ("four is the floor")

Overview

A blood glucose below 4 mmol/L — a common, rapidly reversible emergency, usually from insulin/sulfonylurea therapy. Treatment depends on conscious level and IV access: oral fast carbohydrate if able to swallow, IV glucose or IM glucagon if not.

Recognise

  • Autonomic: sweating, tremor, palpitations, hunger, anxiety
  • Neuroglycopenic: confusion, drowsiness, slurred speech, seizures, coma
  • Often on insulin or a sulfonylurea; missed meal, exercise, alcohol

Red flags

  • Reduced consciousness/seizure; sulfonylurea-induced hypoglycaemia is prolonged → admit/observe

Differentials & how to tell them apart

Stroke/TIAfocal deficit, normal glucose — always check glucose first in any neuro presentation
Seizure (other cause)normal glucose; hypoglycaemia is a reversible cause to exclude
Alcohol intoxicationmay coexist/cause hypoglycaemia — check glucose
Sepsiscan cause hypoglycaemia in severe cases

Investigations

Capillary then lab glucose; identify the cause (drugs, alcohol, Addison’s, insulinoma if unexplained).

Management

Conscious: oral fast carbohydrate; reduced consciousness: IV 20% glucose (or IM glucagon if no access)

  1. 1Check glucose. Conscious and able to swallow: 15–20 g fast carbohydrate, repeat at 15 min, then a long-acting carbohydrate. Reduced consciousness: IV glucose (or IM glucagon if no IV access).Gate: Glucagon is unreliable in sulfonylurea overdose, alcohol, or malnutrition (depleted glycogen) → use IV glucose; sulfonylurea hypoglycaemia is prolonged and needs admission
  2. 2Find and treat the cause; review diabetes medication; recheck glucose and give a snack.
Oral fast-acting carbohydrate — conscious + able to swallow: glucose tablets/juice, then long-acting carb
IV glucose (e.g. 100 mL 20%) — if unable to swallow / IV access
IM glucagon 1 mg — if no IV access (less effective in malnourished/alcohol/sulfonylurea)

Key points

Always check glucose in any altered consciousness/seizure/"stroke" — it is the cheapest reversible cause. Sulfonylurea hypoglycaemia recurs for hours.

Monitor & prognosis

Repeat glucose; observe (esp. sulfonylurea/long-acting insulin); medication review.

Rapidly reversible; recurrent severe hypos need a management review.

Source: JBDS-IP (hypoglycaemia); BNF