Also Known As
Total CO2
TCO2
Carbon Dioxide Content
CO2 Content
Bicarb
HCO3-
Formal Name
Bicarbonate
This article was last reviewed on
This article waslast modified on 14 June 2023.
At a Glance
Why Get Tested?

Bicarbonate can be used to assess and monitor acid-base (acid-alkali / pH) and electrolyte (charged ion) status in conditions known to cause imbalance.

When To Get Tested?

As part of routine electrolyte measurement in blood or when symptoms or medical conditions could indicate problems with acid-base (acid-alkali) balance in the body. It is most useful when measured alongside pH, partial pressure of carbon dioxide (PCO2) and other electrolytes (e.g. sodium, potassium and chloride). It can help detect or monitor disorders as well as the response to treatment.

Sample Required?

A blood sample taken from a vein in the arm is needed for bicarbonate. A blood sample from an artery may be taken at the bedside if blood gases (including calculated bicarbonate) are also being tested.

Test Preparation Needed?

No test preparation is needed before blood is collected. For accurate results, blood should be spun and tested promptly in full and capped tubes. For accurate blood gas measurement (pH, PCO2 and calculated bicarbonate), arterial blood should be collected in a heparin tube that is capped, well mixed, free from air bubbles and analysed immediately at the bedside.

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, sex, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

A significant amount of acid is produced within the normal human body. However, hydrogen ion concentration ([H+], described by pH) must be kept within tight limits to prevent major health problems. The ratio between blood bicarbonate (HCO3-) concentration and partial pressure of carbon dioxide (PCO2) determines blood pH. The kidneys and lungs are important in maintaining acid-base (acid-alkali) balance for normal pH. The kidneys...

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