Chloride (Cl⁻)

What it measures

Chloride is the main extracellular anion and follows sodium in most disorders. It is used with sodium and bicarbonate to evaluate acid–base status and calculate the anion gap.

Specimen and preparation

• Specimen: Serum or lithium-heparin plasma
• Tube: Gold top

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Normal anion gap metabolic acidosis (diarrhoea, renal tubular acidosis)
• Dehydration
• Large volumes of 0.9% saline
• Respiratory alkalosis (compensation)

Causes of low values

• Prolonged vomiting or gastric suction
• Metabolic alkalosis
• Diuretic therapy
• SIADH and water overload
• Chronic respiratory acidosis

Method

Ion-selective electrode

Good to know

Bromide and some other halides give falsely high chloride on ISE.

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