Chloride
Cl· also: Cl-, Chloride
Clinical Overview
Chloride is the major extracellular anion and works with sodium to maintain osmotic balance and fluid distribution. It plays a key role in acid-base balance and is exchanged for bicarbonate in red blood cells. Chloride abnormalities are rarely isolated and usually accompany sodium and acid-base disorders.
Why This Test Matters
Chloride is primarily used to calculate the anion gap (Na − (Cl + HCO3)), which helps classify metabolic acidosis. A normal anion gap metabolic acidosis is associated with hyperchloremia (from diarrhea, renal tubular acidosis, or excessive saline infusion). An elevated anion gap metabolic acidosis (from lactic acidosis, ketoacidosis, aspirin poisoning) usually has normal or low chloride.
Reference RangesWHO/IFCC standards
| Reference Range | Unit | Notes |
|---|---|---|
| 98 – 106 | mEq/L | — |
Also reported in: mmol/L.
What Causes Abnormal Results?
High Cl Causes
- Metabolic acidosis with normal anion gap (diarrhea, RTA, excessive normal saline)
- Respiratory alkalosis (compensation)
- Hyperparathyroidism
- Dehydration
Low Cl Causes
- Vomiting (loss of HCl)
- Metabolic alkalosis
- Chronic respiratory acidosis (compensation)
- SIADH (dilutional)
- Addison's disease
Signs & Symptoms to Watch For
How to Prepare for This Test
No special preparation. Part of the BMP/CMP panel.
Factors That Can Affect Results
- High bromide levels (bromide measured as chloride by some analyzers)
- Lipemia (may interfere with some analyzer methods)
Related Topics
Frequently Asked Questions
What is the anion gap and how is it calculated?
The anion gap = Sodium − (Chloride + Bicarbonate). It represents unmeasured anions in the blood. Normal anion gap is 8–12 mEq/L (using albumin-corrected values). An elevated anion gap means excess acid is present: MUDPILES mnemonic — Methanol, Uremia, DKA, Propylene glycol, Isoniazid/Iron, Lactic acidosis, Ethylene glycol, Salicylates. A normal anion gap metabolic acidosis suggests HCO3 loss (diarrhea, RTA) or chloride gain (saline infusion).