Summary

• Chloride is an electrolyte that helps balance the fluids in your body.
• It helps keep your blood at the right pH (acid-base) balance.
• It works with other electrolytes to help your nerves send signals.
• Chloride is an important component of stomach acid which helps digest food, kill harmful bacteria and control fluid movement in your gut.
• Chloride is often measured as part of the electrolytes group of tests which is routinely done to assess your general health, check your kidneys and your blood pH balance.

What is chloride?

Chloride is an electrolyte that works closely with two other electrolytes, sodium and potassium, to balance your body’s fluids, keep your nerves working properly and help keep your blood at the right pH balance. It also forms stomach acid and helps control fluid movement in your gut.

You take in chloride from your diet, in particular table salt which is made up of sodium and chloride. Any excess chloride is removed by your kidneys and passed into your urine.

How your body uses chloride

Everything we do is controlled and enabled by electrical signals running through our bodies. Sodium, potassium and chloride are electrolytes which are minerals that carry an electrical charge in fluids. They enable cells to pass electrical changes back and forth, which is important for sending signals around the body.

Cells need electrical neutrality to work properly. Sodium and potassium are positively charged, while chloride is negatively charged. Chloride follows sodium and when sodium moves into or out of cells, chloride follows to balance the electric charge. This prevents cells and fluids from becoming electrically unstable.

Nerve signals and muscle movement

Nerves send electrical signals so you can feel touch and pain and control your muscle movements. For example, when your brain tells your hand to pick up a cup, electricity carries the messages from your brain to your hand. This is rather like an electrical cable, except the electrical signals jump from one cell to another.

Sodium and potassium are needed to do this. They make an electrical charge through what is called the sodium-potassium pump.

This works by letting sodium and potassium move in and out of a cell in a precise sequence, creating an electrical change. Sodium and potassium in one cell create an electrical signal that jumps to the next cell, which responds by creating another electrical signal that jumps to the next cell, and so on. In this way, the nerve impulse travels along the nerve like a wave. Once the electrical impulse has passed the cell is reset ready for the next impulse.

Chloride is needed to help stabilise these electrical signals in cells. It stops nerves and muscles from firing too easily, helping to keep signals smooth and controlled.

Fluid balance

Sodium and potassium work to control your body’s fluid balance:

• Potassium is mainly found inside your body’s cells
• Sodium is mainly found outside the cells
• Sodium pulls water out of cells
• Potassium pulls water into cells

For more on balancing body fluids see sodium and potassium.

Acid–base (pH) balance

Chloride helps keep your blood at the right pH so that your blood doesn’t become too acidic or too alkaline. Chloride does this by balancing bicarbonate levels. The less bicarbonate you have in your blood, the more acidic it becomes. The more bicarbonate you have, the more alkaline your blood becomes.

Bicarbonate is a waste product that is made when your body uses oxygen to make energy. Bicarbonate passes from your body’s cells into your blood where it is transported by your red blood cells to your lungs to be breathed out as carbon dioxide.

When bicarbonate reaches the lungs, chloride moves into red blood cells and displaces bicarbonate in what is called the chloride–bicarbonate exchange. This is why the levels of chloride and bicarbonate are often interpreted together. For more on this see blood gases.

Digestion

Chloride forms stomach acid. This acid helps digest food and kill harmful bacteria. Acidic conditions also help release minerals like iron, calcium and magnesium from food to that they can be absorbed. Chloride also helps control fluid movement in the gastrointestinal tract, adding or removing water.

Why get tested?

Chloride is included in the electrolytes group of tests which also include sodium, potassium and bicarbonate. This commonly ordered group of blood tests is used to investigate or monitor a wide range of health conditions such as:

• kidney function
• hydration status
• pH (acid – base) balance
• effects of medications (e.g. diuretics)

Chloride is measured as a component of blood gas analysis to investigate problems with the pH (acid-base) balance, and to monitor treatment.

It can be helpful in an emergency response if someone has:

• severe vomiting or diarrhoea
• an altered mental state such as confusion and reduced consciousness - it helps identify pH disorders that cause to brain dysfunction
• kidney failure
• shock or sepsis
• saline IV treatment

It is also used to confirm metabolic alkalosis in some hormonal or inherited disorders including:

• Hyperaldosteronism
• Cushing syndrome
• Bartter or Gitelman syndrome

Chloride urine test

Measuring chloride in a urine sample can be done when more information is needed. Although a blood test can show how much chloride is in your blood at the time your blood sample is taken, a urine chloride test can show if you kidneys are successfully controlling your chloride levels.

It is helpful in deciding whether low blood chloride levels are due to a problem with your kidneys or a problem elsewhere in your body such as gastrointestinal fluid losses.

Used with other test results, the urine chloride test can help distinguish between vomiting and other forms of gastric losses, and to diagnose problems with how your kidneys are working. This is important so that you can be given the correct treatment.

Having the test

Sample

Blood or urine.

Any Preparation?

None.

Your results

Reading your test report

Your results will be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.

A high blood chloride level is referred to as hyperchloraemia, and a low chloride level is called hypochloraemia.

Reference intervals - comparing your results to the healthy population

Your results will be compared to reference intervals (sometimes called a normal range).

• Reference intervals are the range of results expected in healthy people.
• They are used to provide a benchmark for interpreting a patient's test results.
• When compared against them, your results may be flagged high or low if they sit outside this range.
• Some reference intervals are harmonised or standardised, which means all labs in Australia use them.
• Others are not because for these tests, labs are using different instruments and chemical processes to analyse samples.
• Always compare your lab results to the reference interval provided on the same report.

If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

More information

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.

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