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Bicarbonate is the form in which most of the carbon dioxide in your body is found. A level that is too low or too high can point to a problem with your lungs or kidneys, or to an imbalance of electrolytes.[1]
On this page you can read what bicarbonate is, what the guidelines say about a level that is too low or too high, what affects your level and which other values are best to read alongside it.
Also known as: bicarb, total CO2, TCO2, CO2 content, carbon dioxide in blood. At the lab: HCO3.
Carbon dioxide (CO2) is an odourless, colourless gas. It is a waste product of your metabolism, the process your body uses to make energy from what you eat.[1]
Most of the carbon dioxide in your body is found in the form of bicarbonate (HCO3). Bicarbonate is an electrolyte: a mineral with an electric charge. Electrolytes help regulate the amount of fluid and the acid-base balance (pH) in your body.[1]
Your blood carries carbon dioxide to your lungs, where you breathe it out. Too much or too little carbon dioxide in your blood can be a sign of a health problem.[1]
The test is often part of a group of tests called an electrolyte panel, sometimes as part of a routine check-up. It can also be part of a basic or comprehensive metabolic panel. A panel like this measures different substances in your blood to learn something about your body's chemical balance and metabolism.[1]
The test can help detect or monitor conditions linked to an imbalance of electrolytes. Think of high blood pressure and diseases of the kidneys, lungs or liver.[1]
A doctor may order the test if you have symptoms such as difficulty breathing, confusion, weakness, tiredness, or vomiting or diarrhoea for a long time. The test can also show whether certain medicines are throwing your electrolytes out of balance.[1]
The lab BioProfile works with, Labplusarts, uses a reference value of 22 to 29 mmol/l for bicarbonate (HCO3). The lab considers a level between those limits normal.[2]
| Value | What it can mean | Who it is for |
|---|---|---|
| 22 to 29 mmol/l[2] | The lab calls a value between these limits normal | As the lab reports it, with no split by group |
Source: Labplusarts, the laboratory's reference value for bicarbonate (HCO3).[2]
Too little carbon dioxide in your blood can point to blood that is too acidic. That can have many causes, such as a kidney or liver disease, or diarrhoea that goes on for a long time. A low value can also point to blood that is not acidic enough, because of a problem with the lungs or with breathing, such as breathing fast and deeply. Other conditions can also play a part.[1]
Too much carbon dioxide in your blood can point to a lung disease, to kidneys that are no longer working properly, or to blood that is not acidic enough. That last one can be caused by losing acid, for example through vomiting or dehydration. Other conditions can also play a part.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
Some medicines, prescription or over the counter, can raise or lower the amount of carbon dioxide in your blood. Tell your doctor everything you take. Don't stop taking a medicine on your own, only if your doctor tells you to.[1]
Your lungs and kidneys help remove carbon dioxide. If they have trouble doing so, your acid-base balance can shift and your level can change.[1]
Vomiting or dehydration can make your body lose acid, while long-lasting diarrhoea can make your blood more acidic. Both can affect your level.[1]
Bicarbonate is included in BioProfile 121 and 150.[3]
The BioProfile editorial team wrote this page on 10 October 2026 from the sources below, which we read on 10 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert has yet to check this page; after that check, the expert's name and the date of the check will appear at the top. This page offers explanation, not a diagnosis. Discuss a value outside the range with your GP.
