Chloride (Cl)

Test Overview

A chloride test measures the level of chloride in your blood or urine. Chloride is one of the most important electrolytes in the blood. It helps keep the amount of fluid inside and outside of your cells in balance. It also helps maintain proper blood volume, blood pressure, and pH of your body fluids. Tests for sodium, potassium, and bicarbonate are usually done at the same time as a blood test for chloride.

Most of the chloride in your body comes from the salt (sodium chloride) you eat. Chloride is absorbed by your intestines when you digest food. Extra chloride leaves your body in your urine.

Sometimes a test for chloride can be done on a sample of all your urine collected over a 24-hour period (called a 24-hour urine sample) to find out how much chloride is leaving your body in your urine.

Chloride can also be measured in skin sweat to test for cystic fibrosis.

Why It Is Done

A test for chloride may be done to:

Check your chloride level if you are having symptoms such as muscle twitching or spasms, breathing problems, weakness, or confusion.
Find out whether you have kidney or adrenal gland problems.
Help find the cause for high blood pH. A condition called metabolic alkalosis can be caused by a loss of acid from your body (for example, from a loss of electrolytes through prolonged vomiting or diarrhea). You may also have metabolic alkalosis if your body loses too much sodium or you eat too much baking soda (sodium bicarbonate).

How To Prepare

You do not need to do anything before you have this test.

Tell your doctor if you:

Are taking any medicines.
Are allergic to any medicines.
Are or might be pregnant.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form .

How It Is Done

Blood test

The health professional taking a sample of your blood will:

Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
Clean the needle site with alcohol.
Put the needle into the vein. More than one needle stick may be needed.
Attach a tube to the needle to fill it with blood.
Remove the band from your arm when enough blood is collected.
Put a gauze pad or cotton ball over the needle site as the needle is removed.
Put pressure on the site and then put on a bandage.

Urine test

You start collecting your urine in the morning. When you first get up, empty your bladder but do not save this urine. Write down the time that you urinated to mark the beginning of your 24-hour collection period.
For the next 24 hours, collect all your urine. Your doctor or lab will usually provide you with a large container that holds about 4 L (1 gal). The container has a small amount of preservative in it. Urinate into a small, clean container and then pour the urine into the large container. Do not touch the inside of the container with your fingers.
Keep the large container in the refrigerator for the 24 hours.
Empty your bladder for the final time at or just before the end of the 24-hour period. Add this urine to the large container and record the time.
Do not get toilet paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in the urine sample.

The skin sweat test for chloride is primarily used to test for cystic fibrosis. To learn more, see the topic Sweat Test.

How It Feels

Blood test

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Urine test

There is no pain while collecting a 24-hour urine sample.

Risks

Blood test

There is very little chance of a problem from having a blood sample taken from a vein.

You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.

Urine test

There is no chance for problems while collecting a 24-hour urine sample.

Results

A chloride test measures the level of chloride in your blood or urine. Chloride is one of the most important electrolytes in the blood, along with sodium, potassium, and calcium. Chloride helps keep the amount of fluid inside and outside of your cells in balance.

Normal

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab. Blood chloride levels are checked more often than urine chloride levels. Results are usually available in 1 to 2 days.

Chloride in blood^{footnote 1}
Adults:	96–106 millimoles per litre (mmol/L)[96–106 milliequivalents per litre (mEq/L)]
Newborns:	ranges vary, speak to your health care provider

Chloride in urine^{footnote 1}
Adult:	140–250 mmol per 24 hours (140–250 mEq per 24 hours)
Child (10–14 years):	ranges vary, speak to your health care provider
Child (younger than 6 years):	ranges vary, speak to your health care provider

Abnormal

High chloride levels may be caused by:

Dehydration, such as from diarrhea or vomiting.
Eating a lot of salt.
Kidney disease.
An overactive parathyroid gland (hyperparathyroidism).

Low chloride levels may be caused by:

Conditions that cause too much water to build up in the body, such as with syndrome of inappropriate antidiuretic hormone secretion (SIADH).
Addison's disease.
A condition that raises the pH of the blood above the normal range (metabolic alkalosis).
Heart failure.
Ongoing vomiting.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Taking some medicines, such as corticosteroids, non-steroidal anti-inflammatory drugs (NSAIDs), estrogens, male hormones (androgens), some blood pressure medicines, cholestyramine, and some "water pills" (diuretics).
Failing to collect exactly 24 hours of urine during a 24-hour urine test for chloride.

What To Think About

The results from a blood or urine chloride test do not provide enough information to diagnose a specific disease or problem. Your doctor will talk with you about how your results may be caused by your symptoms or past health.
Potassium chloride (found in salt substitutes) can lower your blood chloride levels but raise your urine chloride levels.
Tests for sodium, potassium, and bicarbonate usually are done at the same time as a blood test for chloride.
The skin sweat test for chloride is used to test for cystic fibrosis. To learn more, see the topic Sweat Test.

References

Citations

Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

Other Works Consulted

Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.

Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.