Bicarbonate

Also written as: CO2, carbon dioxide, total CO2, HCO3

The blood's main acid buffer, reported as CO2, used to judge the body's acid-base balance.

What it measures

The total carbon dioxide carried in the blood, most of which exists as bicarbonate. Bicarbonate is the body's main chemical buffer - it soaks up excess acid and keeps the blood's acidity within a narrow range, regulated by the kidneys and the lungs.

Why a doctor orders it

It is part of the standard electrolyte panel and gives a quick reading of the body's acid-base balance. Clinicians use it to look for states where the blood is too acidic or too alkaline, and to monitor kidney function, breathing problems, and the effects of some medications.

What is generally associated with a higher result

Broadly associated with prolonged vomiting, diuretic use, and lung conditions in which carbon dioxide is retained. It can also reflect a compensation - the kidneys holding on to bicarbonate to balance a breathing issue.

What is generally associated with a lower result

Broadly associated with kidney conditions, prolonged diarrhea, and states that produce excess acid. Slightly low values are also a well known sample artifact, because bicarbonate escapes from blood tubes that sit open or unprocessed too long.

Everyday things that move this number

Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:

Delays in processing the sample, which lower the measured value
Recent vomiting or diarrhea
Diuretic medications
Rapid breathing, for example from anxiety, at the time of the draw
Living at or traveling to high altitude

Questions to take to your appointment

Could this be a sample handling effect rather than a true result?
Does this value fit with my other electrolytes and kidney results?
Could any of my medications, such as diuretics, be shifting it?

Build a printable questionnaire with your own results →

Where to read more

MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .

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