What this test measures
Chloride is the most abundant anion (negatively-charged ion) in serum, balancing the positively-charged sodium and potassium to keep fluid neutral. It is essential for maintaining osmotic pressure, stomach acid production (HCl), and acid-base balance.
Chloride is regulated mainly by the kidneys, alongside sodium. It usually moves with sodium — they rise and fall together in most water-balance disorders — but they can dissociate in acid-base disorders, helping with diagnosis. The "anion gap" (calculated as Sodium − Chloride − Bicarbonate, normal 8–12) is the most useful derived number.
Why it matters
Chloride alone is rarely abnormal — it is interpreted alongside sodium, bicarbonate and the anion gap. In India, low chloride (hypochloraemia) is most often seen with vomiting (loss of HCl), diuretic use, or severe metabolic alkalosis. High chloride (hyperchloraemia) is seen with dehydration, normal anion gap metabolic acidosis (diarrhoea, renal tubular acidosis), excessive saline IV fluids, and rarely renal disease.
The anion gap is one of the most diagnostically powerful numbers in clinical medicine — a high anion gap metabolic acidosis points to diabetic ketoacidosis, lactic acidosis, kidney failure or specific poisonings, while a normal anion gap acidosis points to bicarbonate loss (diarrhoea or renal tubular acidosis).
How to prepare
No fasting required. Routine venipuncture. Mention diuretics, IV fluids in the last 24 hours, severe vomiting / diarrhoea.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Chloride (mEq/L)[1][2] | 98 – 107 | Hypochloraemia (<98). Most often from vomiting (loss of HCl from stomach), nasogastric suction, loop / thiazide diuretics, congestive heart failure with diuretic use, cystic fibrosis (sweat loss), Addison's disease, severe metabolic alkalosis, SIADH (with low sodium). | Hyperchloraemia (>107). Causes — dehydration, diarrhoea (loses bicarbonate, retains chloride), renal tubular acidosis, large-volume normal saline infusion (iatrogenic), respiratory alkalosis (compensation), hyperparathyroidism, some drugs (acetazolamide). Interpret with bicarbonate and the anion gap. |
Using the anion gap to read chloride
| Pattern | Chloride | Bicarbonate | Anion gap | Likely cause |
|---|---|---|---|---|
| Normal | 98 – 107 | 22 – 29 | 8 – 12 | Healthy |
| Vomiting / NG suction | Low | High | Normal | Hypochloraemic metabolic alkalosis |
| Diarrhoea | High | Low | Normal | Normal anion gap metabolic acidosis (bicarbonate loss) |
| Diabetic ketoacidosis | Normal / low | Very low | High (>12) | High anion gap acidosis (ketones) |
| Excess saline IV | High | Low / normal | Normal | Iatrogenic hyperchloraemic acidosis |
Frequently asked questions
Why does chloride matter?
Chloride balances sodium and helps maintain blood volume, stomach acidity and acid-base balance. The most useful derived number is the anion gap, which separates many causes of metabolic acidosis.
Do I need to fast?
No fasting is required for a chloride test.
My chloride is 95 and I have been vomiting. What does that mean?
Vomiting loses stomach acid (HCl), which lowers chloride and raises bicarbonate — classic hypochloraemic metabolic alkalosis. Rehydration with normal saline restores both. Persistent vomiting needs evaluation.
My chloride is 110 and bicarbonate is 18. Is this serious?
A pattern of high chloride and low bicarbonate is normal-anion-gap metabolic acidosis. Common causes are diarrhoea, renal tubular acidosis, and excessive normal saline. Your doctor will calculate the anion gap and treat the underlying cause.
What is the anion gap?
The anion gap = Sodium − (Chloride + Bicarbonate). Normal is 8–12. A raised gap (>12) suggests acid was added (DKA, lactic acidosis, renal failure, poisonings). A normal gap suggests bicarbonate was lost (diarrhoea, renal tubular acidosis).
Can IV fluids change chloride?
Yes — large-volume normal saline (which is 154 mEq/L chloride, higher than serum) raises chloride and can cause "saline-induced acidosis". Balanced solutions (Ringer's lactate, Plasmalyte) avoid this.
Does diet affect chloride?
Most dietary chloride comes from salt (sodium chloride). Very low-salt diets can mildly lower chloride; high-salt diets and chronic dehydration mildly raise it. In healthy people, the kidneys keep it in a tight range.
Related Kidney / Electrolytes tests
Tests commonly ordered alongside CHLORIDE, or that help interpret an unexpected result.
Sources & references
- NIH MedlinePlus — Chloride Blood Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Hyperchloremia · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Laboratories — Chloride, Serum · accessed 2026-05-30T00:00:00.000Z
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