Non-clinical sciences/Lab medicine · Acid–base

Metabolic acidosis (raised anion gap)

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What it means

↓pH, ↓HCO₃, raised anion gap [Na − (Cl + HCO₃); normal 8–12] — unmeasured acid anions. MUDPILES: Methanol, Uraemia, DKA, Propylene glycol, Iron/Isoniazid, Lactic acidosis (sepsis/shock), Ethylene glycol, Salicylates.

Worked example

DKA: pH 7.15, HCO₃ 8, glucose 25, ketones 5, anion gap 24.

In the exam

A breathless diabetic has pH 7.15, HCO₃ 8, an anion gap of 24 and heavy ketonuria.

What settles it

Raised-gap acidosis adds unmeasured ACID (lactate/ketones); normal-gap acidosis is HCO₃ loss replaced by chloride (diarrhoea/RTA).

Classically confused with

Metabolic acidosis (normal anion gap)

Source: StatPearls — Anion gap