Summary

• Bicarbonate is formed when your body uses oxygen to make energy.
• Bicarbonate travels through your blood to your lungs where it is breathed out as carbon dioxide.
• Bicarbonate helps keep your blood from being too acidic or too alkaline. It acts like a sponge soaking up excess acid.
• The less bicarbonate you have in your blood, the more acidic your blood becomes. The more bicarbonate, the more alkaline your blood becomes.
• The regulation of acidity and alkalinity is called the pH balance.
• Normal blood pH must stay in a narrow range to ensure your body functions properly.
• Measuring the amount of bicarbonate in your blood is used to help check your pH level.
• It is almost always tested together with sodium, potassium, and chloride, to make sure all levels are in balance with each other.
• These are called electrolytes and together they keep the right pH balance and the right balance of fluids in your body.
• Blood gases testing which measures the levels of oxygen, carbon dioxide and bicarbonate in the blood is commonly ordered in hospital settings, particularly in emergency departments, intensive care units, and respiratory clinics.

What is bicarbonate?

Bicarbonate is produced when your cells make energy from oxygen.

• Your lungs bring oxygen into your body. Once taken up by your blood, oxygen sticks to haemoglobin, the red protein in your red blood cells.
• Oxygen is transported all over your body where it is used by all your body’s cells to make energy.
• In order to produce energy, oxygen binds with glucose – which you get from the food you eat. This releases water and bicarbonate.
• Bicarbonate passes from the cells into the blood where it attaches to haemoglobin and is transported back to your lungs.
• In your lungs, bicarbonate is separated from the haemoglobin and is breathed out as carbon dioxide.

Your pH (also known as acid-base) balance

Your body needs bicarbonate to help keep a normal pH balance. Bicarbonate works together with sodium, potassium and chloride to keep this balance.

The less bicarbonate you have in your blood, the more acidic it becomes. The more bicarbonate you have, the more alkaline your blood becomes.

Your kidneys help keep acidity levels stable when they filter your blood by adjusting bicarbonate levels.

Why get tested?

The bicarbonate test measures the total carbon dioxide in your blood in these three forms:

• bicarbonate, the dominant form
• carbonic acid
• carbon dioxide dissolved in blood

Since it measures all three forms at once, the bicarbonate test gives an estimate of your pH balance. This is usually enough in most clinical situations. If a more accurate assessment of your pH balance is needed, measurements of gases dissolved in the blood may also be done. Blood gas testing measures oxygen and carbon dioxide levels as well as bicarbonate. For more on this see Blood gases (arterial) and Blood gases (venous).

Bicarbonate may be measured along with sodium, potassium, and possibly chloride in an electrolyte profile. When doctors want to understand a person’s pH and fluid balance, they don’t need to measure every electrolyte in the body. The results of three electrolytes are usually enough to provide critical information into the pH and fluid balance.

Having the test

Sample

Blood.

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.

High levels of bicarbonate

When bicarbonate levels are higher than normal, it suggests that your body is having trouble maintaining its pH balance. This could be due to either too much acid being removed from your body, or too much bicarbonate being retained. Both imbalances may be due to a wide range of problems.

High bicarbonate levels can be caused by severe vomiting, dehydration, chronic lung-related problems, such as emphysema, and some hormonal disorders such as Cushing's disease.

Low levels of bicarbonate

Low levels of bicarbonate are seen when the body is too acidic or loses too much bicarbonate. Low levels are associated with kidney disease, chronic diarrhoea, diabetic ketoacidosis, Addison's disease, lactic acidosis and some toxins such as methanol.

Some medications can increase bicarbonate levels especially diuretics. Other medications may cause slightly low levels. Your doctor can advise if this appears to be a problem.

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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