Chloride Test
Note: this site is for informational purposes only. To view test results or book a test, use the NHS app in England or contact your GP.
A chloride test measures the level of chloride in a blood sample (and sometimes urine) to assess electrolyte balance in the body. It is used to help diagnose and monitor acid–base imbalances, dehydration, kidney disease, and conditions affecting fluid balance.
Why get tested?
To determine if there is a problem with your body’s acid-alkali (pH) balance and to monitor treatment.
When to get tested?
If your doctor thinks that you have an electrolyte imbalance.
Sample required?
A blood sample taken from a vein in the arm or a urine sample.
Test preparation needed?
None
Common questions
Blood chloride may be useful along with sodium, to evaluate problems with the acid-base balance in the body, and to monitor treatment.
A blood chloride test may be requested to help evaluate kidney function and acid-base status. It may also be requested if you are in hospital and receiving intravenous (IV) fluids. If your sodium measurement is abnormal, the doctor may look at whether the chloride measurement changes in the same way. This may help the doctor to workout if there is also a problem with acid or base and may help guide treatment.
A severe elevation or loss of this electrolyte can indicate a serious fluid and electrolyte imbalance. The type of medical treatment depends on the cause of the problem.
Increased levels of chloride (called hyperchloraemia) usually indicate dehydration, but can also occur with any other problem that causes high blood sodium. Hyperchloraemia also occurs when too much alkaline fluid is lost from the body (producing metabolic acidosis), or when a person hyperventilates (causing respiratory alkalosis).
Decreased levels of chloride (called hypochloraemia) occur with any disorder that causes low blood sodium. Hypochloraemia also occurs with prolonged vomiting or gastric suction, chronic diarrhoea, emphysema, or other chronic lung disease (causing respiratory acidosis), and with loss of acid from the body (called metabolic alkalosis).
Drugs that affect sodium blood levels will also cause changes in chloride such as the use of diuretics. In addition, the chronic use of laxatives or taking more than the recommended dosage of antacids can also cause low blood chloride.
Most chloride exists as a compound with sodium in the form of sodium chloride, or table salt.
The same treatments used to treat sodium imbalances – diuretics, fluid replacement, etc – may be used to treat chloride imbalance.