Chloride Unit Converter
Chloride Unit Converter
Convert chloride between mmol/L, mEq/L and mg/dL. Chloride is monovalent, so mmol/L and mEq/L are the same number — and the result only means something once it is read against sodium.
Chloride converter
Monovalent — mmol/L = mEq/LChloride 102 mmol/L
Formula and conversion factors
mg/dL = mmol/L × 3.545
mEq/L = mmol/L (chloride is monovalent)
- 0.282087
- 10 ÷ 35.45, the atomic mass of chlorine — mg/dL × 10 ÷ MW gives mmol/L
- mEq/L
- chloride carries a single negative charge, so millimoles and milliequivalents are the same number
- sodium minus chloride
- the difference between the two, normally about 36 mmol/L, is the quickest bedside read on whether an acidosis has a raised gap
- 0.9% saline
- contains 154 mmol/L of chloride against a plasma value near 100, which is why large volumes produce a hyperchloraemic acidosis
Worked example
Chloride 102 mmol/L
102.0 mmol/L — the unit almost every laboratory reports
102.0 mmol/L = 102.0 mEq/L — chloride is monovalent, so the two are the same number
102.0 ÷ 0.282087 = 361.6 mg/dL, a mass unit not used on serum reports
Within the adult reference interval of 98–107 mmol/L
Thresholds across the units
| mmol/L | mEq/L | mg/dL | |
|---|---|---|---|
| Adult reference interval | 98 – 107 | 98 – 107 | 347 – 379 |
| Hypochloraemia | < 98 | < 98 | < 347 |
| Hyperchloraemia | > 107 | > 107 | > 379 |
| Chloride in 1 litre of 0.9% saline | 154 | 154 | 546 |
| Chloride in 1 litre of Hartmann’s solution | 111 | 111 | 394 |
| Chloride in 1 litre of Plasma-Lyte 148 | 98 | 98 | 347 |
Reading chloride against sodium
| Pattern | Suggests | Next step |
|---|---|---|
| Chloride high, bicarbonate low, gap normal | Hyperchloraemic (normal anion gap) acidosis | Saline load, diarrhoea, renal tubular acidosis — check the urine anion gap |
| Chloride low, bicarbonate high | Metabolic alkalosis | Vomiting, nasogastric loss, diuretics — measure a urinary chloride |
| Chloride low out of proportion to sodium | Raised anion gap acidosis, or a bromide interference | Calculate the gap; ask about bromide-containing preparations |
| Sodium minus chloride well above 36 | Unmeasured anions present | Calculate the anion gap formally and correct for albumin |
The electrolyte that only means something in company
Chloride is reported in mmol/L in the United Kingdom and in mEq/L in the United States, and the two are the same number, because chloride carries a single negative charge. The mg/dL column converts by 10 ÷ 35.45, the atomic mass of chlorine, or 0.2821 mmol/L per mg/dL. As with the other monovalent electrolytes, the arithmetic is trivial and the interpretation is not: a chloride read on its own is close to uninformative.
Its first use is in the anion gap. Chloride and bicarbonate are the two measured anions, so a chloride that rises as bicarbonate falls preserves the gap and points at a hyperchloraemic, normal anion gap acidosis, while a chloride that stays put as bicarbonate falls opens the gap and points at lactate, ketones, renal failure or a toxin. The difference between sodium and chloride, normally around 36 mmol/L, is the fastest bedside version of that question.
The second use is iatrogenic. A litre of 0.9% sodium chloride carries 154 mmol/L of chloride against a plasma value near 100, so large volumes reliably produce a hyperchloraemic metabolic acidosis; balanced crystalloids carry less — 111 mmol/L in Hartmann’s solution, 98 in Plasma-Lyte 148 — and do not. Randomised evidence in critically ill adults has favoured balanced solutions over saline for major adverse kidney events, and recognising a saline-induced acidosis prevents a fruitless search for lactate or ketones.
Two further points are worth holding. A low chloride with a high bicarbonate is a metabolic alkalosis, and a urinary chloride below about 20 mmol/L identifies the saline-responsive causes — vomiting, nasogastric loss, diuretics that have worn off — from the saline-resistant ones such as hyperaldosteronism. And chloride is measured by ion-selective electrodes that some halides interfere with, so bromide, and at high concentrations salicylate on certain analysers, can produce a spuriously high chloride and an artefactually low or negative anion gap.
Frequently asked questions
Is mmol/L the same as mEq/L for chloride?
Yes. Chloride is monovalent, so one millimole carries one milliequivalent of charge and the two numbers are identical. A chloride of 102 mmol/L is 102 mEq/L, and no conversion should be applied.
How do I convert chloride from mg/dL to mmol/L?
Multiply by 0.2821, which is 10 divided by the atomic mass of chlorine, 35.45. A value of 360 mg/dL is 101.6 mmol/L. To go the other way, multiply the mmol/L figure by 3.545.
Why does saline cause a high chloride?
A litre of 0.9% sodium chloride contains 154 mmol/L of chloride against a plasma value near 100. Large volumes therefore raise plasma chloride, displace bicarbonate and produce a hyperchloraemic metabolic acidosis with a normal anion gap.
What does the sodium minus chloride difference tell me?
It is a quick screen for the anion gap. The difference is normally about 36 mmol/L; a much larger difference suggests unmeasured anions and a raised gap, while a normal difference with a low bicarbonate suggests a hyperchloraemic acidosis.
Can a chloride result be falsely high?
Yes. Chloride is measured by ion-selective electrodes that other halides can cross-react with, so bromide — and at high concentrations salicylate on some analysers — produces a spuriously high chloride and an artefactually low or even negative anion gap.
Related calculators
References
- Semler MW, Self WH, Wanderer JP, et al. Balanced crystalloids versus saline in critically ill adults. N Engl J Med. 2018;378(9):829–839.
- Berend K, van Hulsteijn LH, Gans ROB. Chloride: the queen of electrolytes? Eur J Intern Med. 2012;23(3):203–211.
- Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.