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.
- Have had bleeding problems or take blood-thinners, such as aspirin or warfarin (Coumadin).
- 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(What is a PDF document?).
How It Is Done
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.
- 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 1 gal (4 L). 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. For more information, see the medical test Sweat Test.
How It Feels
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.
There is no pain while collecting a 24-hour urine sample.
There is very little chance of a problem from having 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.
- Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.
There is no chance for problems while collecting a 24-hour urine sample.
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.
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 urine
140–250 mEq per 24 hours or 140–250 mmol per day
| Child (10–14 years):|
64–176 mEq/24 hours or 64–176 mmol/day
|Child (younger than 6 years):|
15–40 mEq/24 hours or 15–40 mmol/day
High chloride levels may be caused by:
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:
- The amount of water in your body. If you are dehydrated, your chloride level is increased and if you are overhydrated, your chloride level is decreased.
- Some medicines, such as corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), estrogens, male hormones (androgens), some blood pressure medicines, cholestyramine (such as Questran), 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 medical history.
- 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. For more information, see the topics Sodium (Na) in Blood, Potassium (K) in Blood, and Bicarbonate.
- The skin sweat test for chloride is used to test for cystic fibrosis. For more information, see the topic Sweat Test.
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.
|Primary Medical Reviewer||Kathleen Romito, MD - Family Medicine|
|Specialist Medical Reviewer||Brian D. O'Brien, MD - Internal Medicine|
|Last Revised||May 4, 2010|