Chloride (serum or urine)

Chloride is an electrolyte that, together with sodium, maintains the body’s balance of water and acidity. Testing blood or urine helps the doctor understand the cause of dehydration, prolonged vomiting or diarrhoea and acid-base balance disorders. It is usually performed alongside sodium and potassium.

Who is this test for

• you have prolonged vomiting or severe diarrhoea, especially in a young child or older person;
• you feel very thirsty, weak or confused and the doctor suspects dehydration;
• you take diuretics or other medicines that change electrolyte balance;
• you have kidney, heart or liver disease or diabetes, so electrolytes are monitored regularly;
• the doctor is investigating an acid-base balance disorder, in which urine chloride helps identify the cause;
• you are preparing for surgery or having a general health check.

What the test reveals

Chloride generally moves together with sodium in the body, so its blood level most often changes when sodium or the amount of water in the body changes. When stomach fluids are lost, for example through prolonged vomiting, chloride is also lost. The relationship between chloride and other electrolytes also shows the doctor whether the blood is too acidic or too alkaline.

Urine chloride shows how much the kidneys excrete. The doctor requests it when causes of a disorder need to be distinguished, for example chloride loss through vomiting from the effect of diuretics.

The test and preparation

For the blood test, a sample is taken from a vein, and collection takes a few minutes. You do not need to fast unless other tests requiring fasting are being performed the same day. Drink as usual and do not stop medicines without discussing this with your doctor.

For the urine test, a single sample is submitted or, if the doctor requests it, urine collected over 24 hours. Bring the sample as soon as possible, ideally within 2 hours.

What your results mean

In adults, blood chloride is approximately 97 to 108 mmol/L, and the interval printed on the report applies. The doctor interprets it alongside sodium, potassium, your symptoms, medicines and other results.

• Elevated chloride: most often accompanies dehydration and high sodium. It also occurs when the body loses alkaline substances, for example through prolonged diarrhoea or some kidney diseases, and after infusions containing large amounts of saline.
• Low chloride: most often accompanies prolonged vomiting, diuretic use or low sodium due to excess water in the body, for example in heart failure. With prolonged vomiting, the blood often becomes too alkaline.
• Urine chloride: a low level suggests that the kidneys are conserving chloride, for example after vomiting, while higher levels occur with diuretics and in some kidney diseases. There is no single “normal” value, because it depends on salt intake.

If you have confusion, severe weakness, an irregular heartbeat or cannot keep fluids down alongside an electrolyte disorder, go to an emergency department immediately or call 194 or 112.

How to arrange testing

You can come for blood collection without an appointment or referral at one of our branches throughout Croatia (listed on the Contact page). You can also submit a urine sample without a referral or appointment at any branch. Prices for all tests and panels are available in the price list. Chloride is included in the Extended preventive panel, alongside sodium, urea, creatinine, a blood count and other tests.

Frequently asked questions

Is chloride the same as salt?

Not exactly. Table salt is sodium chloride, so we consume chloride mainly through salt. However, blood chloride does not show how much salt you eat, because healthy kidneys excrete excess salt in urine.

Why is chloride tested alongside sodium and potassium?

These electrolytes work together to maintain water and acid balance, so the doctor can best assess the cause of a disorder by looking at them together. Read more in the articles on sodium and potassium.

Does blood chloride show cystic fibrosis?

No. In cystic fibrosis, chloride is elevated in sweat, not blood. A special sweat test is performed for this, on a doctor’s referral.

Can heavy sweating change chloride?

Water and salts are lost through sweat. During prolonged exertion in heat or with fever, this can lead to dehydration and electrolyte changes, especially if you drink too little.