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Chlorides in the urine
Last reviewed: 05.07.2025
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The amount of chlorine in the urine depends on its content in the food. In infants, very little chlorine is excreted in the urine, since its content in breast milk is low. The transition to mixed feeding leads to a significant increase in the chlorine content in the urine. The amount of chlorine in the urine increases in accordance with the ever-increasing consumption of table salt. Approximately 90% of the chlorides in food are excreted in the urine and only 6% in sweat.
Reference values (norm) of chlorine excreted in urine
Age |
Amount of chlorine, meq/day (mmol/day) |
Children under 1 year Children Later |
2-10 15-40 110-250 |
Determination of the chlorine content in urine has an important diagnostic value in critically ill patients undergoing intensive care. This study is of particular importance for establishing the causes of metabolic alkalosis and the possibility of its correction by introducing chlorine. The following types of metabolic alkalosis are distinguished.
- Chloride-sensitive alkalosis with urinary chloride concentrations below 10 mmol/L is the most common form of metabolic alkalosis and is usually associated with extracellular fluid volume depletion. It may occur with gastrointestinal chloride losses (vomiting, gastric aspiration, villous adenoma, and congenital chloridorhea) or with diuretic use (due to concomitant extracellular fluid volume depletion and hypokalemia). It should always be taken into account that large doses of diuretics may even increase urinary chloride levels; this should be kept in mind when assessing metabolic alkalosis and urine chloride measurements. Posthypercapnic states due to persistent renal bicarbonate retention, excessive bicarbonate administration, or repeated blood transfusions (citrate overload) may also cause chloride-sensitive metabolic alkalosis.
- Chloride-resistant alkalosis with urinary chloride levels above 20 mmol/L is much less common. Except for cases of Bartter syndrome and magnesium deficiency, this type of alkalosis usually involves hypertension and the extracellular fluid volume is not reduced. Other causes of this type of alkalosis include primary aldosteronism, Cushing's syndrome, renal artery stenosis, Liddle's syndrome, hypercalcemia, and severe hypokalemia.
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