Reference values — Chloride (serum / plasma)
Chloride is the major extracellular anion. Pregnancy-related dilution and mild respiratory alkalosis may shift chloride slightly, but most values remain within the adult range.
| Units | Nonpregnant Adult | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| mEq/L (mmol/L) | 102 – 109 | 101 – 105 | 97 – 109 | 97 – 109 |
Pregnancy physiology
Maternal plasma volume expansion leads to mild electrolyte dilution. Chronic respiratory alkalosis of pregnancy increases renal bicarbonate loss, which may slightly increase serum chloride (compensatory hyperchloremia).
Causes of elevated chloride (hyperchloremia)
- Dehydration or volume depletion
- Prolonged diarrhea (bicarbonate loss)
- Renal tubular acidosis
- Normal anion-gap metabolic acidosis
- Hypernatremia
- Hyperparathyroidism
- Medications: acetazolamide, estrogens, steroids, NSAIDs
- Bromide ingestion (lab artifact)
Causes of decreased chloride (hypochloremia)
- Metabolic alkalosis
- Vomiting or gastric suction (loss of HCl)
- Diarrhea
- Heart failure
- SIADH
- Adrenal insufficiency
- Salt-wasting nephropathies
- Burns / excessive fluid loss
- Loop or thiazide diuretics
Serum chloride should be interpreted with acid–base status and volume assessment.
References
- Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114:1326–31.
- Wallach J. Interpretation of Diagnostic Tests. 8th ed. LWW; 2007.
- Fischbach FT, Dunning MB. Manual of Laboratory and Diagnostic Tests. 7th ed. LWW; 2004.