About Chloride
Chloride is the most abundant negatively charged electrolyte in the blood and works closely with sodium to maintain fluid balance, blood pressure, and acid-base equilibrium. Most chloride abnormalities mirror sodium changes — dehydration raises both, overhydration lowers both — but isolated low chloride (hypochloraemia) with high bicarbonate points specifically to metabolic alkalosis from vomiting, diuretic use, or adrenal hormone excess. Chloride is rarely acted upon in isolation and is most useful as part of the anion gap calculation.