Chloride (Cl⁻)

The main anion in blood — tracks with sodium and hydration status.

What it is

Chloride is the primary extracellular anion. It moves in parallel with sodium to maintain electrical neutrality. Chloride is used to calculate the anion gap — a diagnostic tool for acid-base disorders.

Why it matters

Chloride abnormalities rarely occur in isolation. They are most useful as part of interpreting electrolyte and acid-base balance. Hypochloraemia (low chloride) commonly occurs with protracted vomiting — relevant during treatment when nausea and emesis are common.

How to test

Standard electrolyte panel.

This information is for educational purposes only. Always discuss testing and interpretation of results with your care team.

Optimal range

98–107 mmol/L.

How often

Each oncology blood panel.