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COMPREHENSIVE METABOLIC PANEL (CMP)
Also printed as: Carbon dioxide · Bicarbonate · HCO3 · Total CO2
Educational only — not medical advice.
This test measures bicarbonate, the buffer your body uses to keep blood from drifting too acidic or too alkaline. It is not the same thing as the carbon dioxide you breathe out, though the two are connected. Your kidneys and lungs adjust it together.
CO2 is a balance marker. It is most informative when read with chloride, sodium, and potassium, because the pattern across all four is what describes acid-base status — no single value does.
TYPICAL ADULT RANGE
Many labs report roughly 22–29 mmol/L for adults. Ranges vary by lab. Reported in mmol/L.
Reference ranges vary by lab, by method, and by age and sex. Always read your own result against the range printed on your report.
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Mildly low bicarbonate has common, undramatic explanations: hyperventilating slightly during the draw, a recent bout of diarrhea, a very low-carbohydrate diet, or hard exercise beforehand. Some medications lower it as an expected effect. Persistent lows are the kind of thing your doctor will want to look at alongside kidney markers and your breathing, rather than treat as a standalone finding.
Higher bicarbonate often follows fluid or acid loss — vomiting, certain diuretics, or heavy antacid use are typical contributors. Chronic changes in breathing patterns can also raise it as the body compensates. It is generally interpreted as part of the electrolyte pattern rather than on its own, so bring the whole panel to your doctor rather than this single line.
Your doctor is the one who can read this number against your history, symptoms, and medications.
Educational only — not medical advice. Lab results only mean something alongside your history, symptoms, medications, and the rest of your panel. Bring questions to your doctor; they are the one who can interpret your results for you.
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