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prognia.

Critical care

Anion Gap

4 inputsCritical care

Screen for unmeasured anions — HAGMA work-up.

Anion Gap calculator

Result

14mmol/L

High AG (>12). Corrected: 14 mmol/L — MUDPILES?

Corrected AG adjusts for hypoalbuminaemia (add 2.5 per 10 g/L below 40).

100 to 170 mmol/L

70 to 130 mmol/L

5 to 45 mmol/L

10 to 55 g/L

How to use it

  1. 1

    AG = Na − (Cl + HCO₃). Normal 8–12 mmol/L.

  2. 2

    Correct for albumin. Each 10 g/L below 40: add 2.5 to AG. Hypoalbuminaemia masks HAGMA.

  3. 3

    MUDPILES mnemonic. Methanol, Uraemia, DKA/alcoholic ketoacidosis, Propylene glycol, Isoniazid/iron, Lactate, Ethylene glycol, Salicylates.

When to use it

Metabolic acidosis work-up
HAGMA (AG > 12): identify culprit from MUDPILES. NAGMA: FENa, UAG, RTA.
ICU acid-base
Calculate delta ratio (ΔAG/ΔHCO₃) to identify mixed disturbances.
DKA monitoring
Normalising AG (not glucose) confirms DKA resolution → begin transition to SC insulin.

A reference for clinicians and students, not medical advice. A score supports a decision; it does not make one. Check every result against the patient in front of you and your local protocol.

At a glance

Specialty
Critical care
Inputs
4
Type
Formula

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