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 one-time random sample of urine or on a sample of all your urine collected over a 24-hour period (called a 24-hour urine sample). This can help 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

• In general, there's nothing you have to do before this test, unless your doctor tells you to.
• For 24-hour urine collection, your doctor or lab will usually give you a large container that holds about 1 gallon.

How It Is Done

Blood test

A health professional uses a needle to take a blood sample, usually from the arm.

Urine test

This test is usually done at home. You must collect all the urine you produce in a 24-hour period.

Timed urine collection

You collect your urine for a period of time, such as over 4 or 24 hours. Your doctor will give you a large container that holds about 1 gallon. A small amount of preservative may be in the container. You will use the container to collect your urine.

• When you first get up, you empty your bladder.

  But don't save this urine. Write down the time you began.

• For the set period of time, collect all your urine.

  Each time you urinate during this time period, collect your urine in a small, clean container. Then pour the urine into the large container. Don't touch the inside of either container with your fingers.

• Don't get toilet paper, pubic hair, stool (feces), menstrual blood, or anything else in the urine sample.
• Keep the collected urine in the refrigerator for the collection time.
• Empty your bladder for the last time at or just before the end of the collection period.

  Add this urine to the large container. Then write down the time.

How It Feels

Blood test

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Urine test

This test usually doesn't cause any pain or discomfort.

Risks

Blood test

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Urine test

There is very little chance of having a problem from this test.

Results

Normal

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

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.