This article is from the Interpretation Of Lab Test Profiles, by Ed Uthman uthman@neosoft.com with numerous contributions by others.
Increased serum anion gap reflects the presence of unmeasured
anions, as in uremia (phosphate, sulfate), diabetic ketoacidosis
(acetoacetate, beta-hydroxybutyrate), shock, exercise-induced
physiologic anaerobic glycolysis, fructose and phenformin
administration (lactate), and poisoning by methanol (formate),
ethylene glycol (oxalate), paraldehyde, and salicylates. Therapy
with diuretics, penicillin, and carbenicillin may also elevate
the anion gap.
Decreased serum anion gap is seen in dilutional states and
hyperviscosity syndromes associated with paraproteinemias.
Because bromide is not distinguished from chloride in some
methodologies, bromide intoxication may appear to produce a
decreased anion gap.
 
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