Blood chloride: what it is, what it tells you and when it’s tested

Chlorine circulates in your blood as chloride, the same as in table salt. After sodium it is the most common salt in your blood, and it almost always moves with sodium. It helps balance your body’s water and the acidity of your blood. It has nothing to do with swimming-pool chlorine.

When it’s tested

Doctors almost always order it together with sodium and potassium, the electrolytes. They ask for it with vomiting or diarrhoea that lasts, with dehydration, with kidney or heart disease, or during treatment with diuretics or a drip.

On its own it says little. It moves with sodium, and when it is out of range without sodium it usually points to a problem with the blood’s acidity, which other tests show. So it is mainly useful when you are ill, often in hospital.

That is why Rosa does not test it. Instead it measures sodium, potassium, creatinine and eGFR, which show how your water, salts and kidneys are doing.

What it tells you, and what it does not

If it rises or falls together with sodium, the problem is usually water: too little or too much.

If it changes on its own, your doctor thinks of the blood’s acidity: for example diarrhoea that makes you lose bicarbonate, or vomiting that makes you lose stomach acid.

On its own it does not show the cause. That needs sodium, bicarbonate, kidney tests and the story of how you feel.

That is why it is read together with other tests:

Normal blood chloride levels

The lab decides what is normal. Many lab reports give 98 to 107 mmol/L. Some use a slightly lower range. The one printed on your report is what counts.

For chloride, mmol/L and mEq/L are the same: the number does not change.

The blood test usually needs nothing special. It is done together with your other blood tests.

What your result means

Find the row for your result, in mmol/L. Which values need a doctor? Below 98 or above 107, especially if your sodium is out of range too or you feel unwell.

If your chloride is high or low

What raises and what lowers chloride

The most common causes, in each direction.

What can skew the result

A few things change it without any disease. It helps to know them before your blood test.

When to worry

Talk to your doctor if:

Frequently asked questions

What are normal blood chloride levels? Many lab reports give 98 to 107 mmol/L, some a slightly lower range. The range on your own report is what counts.

Are chloride and chlorine the same thing? In the blood, chlorine is always present as chloride, and that is what the test measures. It is not the chlorine in swimming pools.

Is high blood chloride dangerous? Just above the limit, it often means you drank too little, and it settles. If it stays high, or you feel unwell, your doctor looks for the cause with other tests.

Does table salt raise blood chloride? If your kidneys are healthy, it usually changes little: they clear the extra. Salt matters mostly for blood pressure.

Does Rosa test chloride? No. Rosa measures sodium, potassium, creatinine and eGFR, which show how your water, salts and kidneys are doing. If your doctor wants chloride, they order it separately.

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