A CO₂ of 15 on a blood test
15 mmol/L
Below the reference range
CO₂ (bicarbonate) of 15 mmol/L is below the usual reference range by commonly reported adult reference ranges
| Where it fallscommonly reported adult reference ranges | Below the reference range |
|---|---|
| CO₂ (bicarbonate) | 15mmol/L |
| Usual reference range | 22 – 29mmol/L |
| Markedly low | under 15mmol/L |
| Below the reference rangethis reading | 15 – 21mmol/L |
| Normal | 22 – 29mmol/L |
| Above the reference range | 30 – 37mmol/L |
| Markedly raised | 38 and abovemmol/L |
Notes
- One reading is not a diagnosis. CO₂ (bicarbonate) moves with the balance between acid produced and acid excreted — kidney function, breathing rate, vomiting, diarrhoea and several medicines. A clinician reads it against your history and usually against a repeat, not on its own.
- Reference ranges differ between laboratories. The bands above follow commonly reported adult reference ranges. Your own report prints the range its analyser was calibrated against, and that printed range is the one to compare against — a difference of a few units between labs is normal and does not mean either is wrong.
- The "CO₂" on a metabolic panel is not the carbon dioxide in your breath. It is total carbon dioxide content, which is almost entirely bicarbonate — the body's acid buffer. It is not the same measurement as the pCO₂ on a blood gas, and confusing the two is a common misreading.
- A low value means acid is accumulating or base is being lost. Kidney disease, uncontrolled diabetes, prolonged diarrhoea and several medicines including metformin and topiramate all do it. A high value most often follows vomiting or diuretic use, both of which lose acid.
What co2 (bicarbonate) of 15 mmol/L means
A result of 15 mmol/L falls in Below the reference range by commonly reported adult reference ranges.
The usual reference range is 22 – 29 mmol/L.
Reading it next to the rest of the panel
Almost no blood test answers a question on its own. Each one narrows the field, and what narrows it further is the value sitting beside it on the same report — which is why a printout with one figure circled is harder to interpret than the whole page.
The bands here come from a named source rather than a rounded rule of thumb. A threshold is a decision point somebody argued for in print, and knowing which document a line comes from is what separates a meaningful result from a borderline one.
Nearby sizes
Read more
- CBC Normal Ranges — What Each Line on the Result MeansA value marked high or low on a CBC is common and is often not significant on its own. The pattern across lines is what a clinician reads.
- eGFR Normal Range: Above 90, and the Stages Below IteGFR is an estimate built from creatinine, age and sex — and the estimate is better than the raw creatinine it comes from, for a reason worth understanding.
- TSH Normal Range: 0.4–4.0 mIU/L, and the Number Moves BackwardsTSH runs opposite to the gland it measures. High TSH means the thyroid is underactive, and that inversion catches almost everyone reading their own result.
- Cholesterol Numbers: What Total, LDL, HDL and Triglycerides MeanA lipid panel reports four numbers and the one printed largest — total cholesterol — is the least useful of them.