Hyperchloraemia is the term used for increased blood chloride levels. This is often linked with dehydration.
It can also occur alongside other problems that lead to high sodium levels, which is also taken into account. For example, use of diuretics (water tablets) that affect sodium levels can also change chloride levels. Long-term use of laxatives or high-dose antacids can also cause low blood chloride.
Other causes include loss of excessive alkaline fluid, which can lead to metabolic acidosis, or hyperventilation, which can lead to respiratory alkalosis.
Chloride is usually not raised on its own and is commonly interpreted in the context of other blood test results. An isolated elevation in chloride is often unlikely to be clinically significant.