Almost every resident has an anion gap talk.  Many students learn MUDPILES – I prefer KILU (An anion gap puzzle that explains KILU).  But many learners do not know these particular pearls.

1. A gap of 25 or greater generally has a discoverable cause, 30 or greater almost certain – Diagnostic Importance of an Increased Serum Anion Gap | NEJM
2. The anion gap does not accurately screen for lactic acidosis in emergency department patients, i.e. check lactic acid levels if you suspect lactic acidosis do not rely on the anion gap
3. Most patients with mildly elevated anion gaps (15-19) do not need immediate evaluation.  You should use clinical judgment prior to evaluating such gaps.
4. The influence of albumin on the expected anion gap  This article describes the precise formula.  We use albumin times 3 as a reasonable estimate.