Bicarbonate
Serum bicarbonate reflects the metabolic component of acid-base balance and drifts slightly with age as chronic kidney function and respiratory patterns change.
Unit: mmol/L · 12 groups · age and sex · 1 source
Filed under panels: Electrolyte Panel · topics: Metabolic , Renal , Electrolytes
Bicarbonate by age and sex
| Age (years) | Males (mmol/L) | Females (mmol/L) |
|---|---|---|
| 20-29 | median 26 middle 90% 22 to 30 | median 24 middle 90% 21 to 28 |
| 30-39 | median 26 middle 90% 23 to 30 | median 25 middle 90% 21 to 29 |
| 40-49 | median 26 middle 90% 22 to 30 | median 25 middle 90% 21 to 29 |
| 50-59 | median 26 middle 90% 22 to 30 | median 26 middle 90% 22 to 29 |
| 60-69 | median 26 middle 90% 21 to 30 | median 26 middle 90% 22 to 30 |
| 70+ | median 26 middle 90% 22 to 30 | median 26 middle 90% 22 to 30 |
Download Bicarbonate percentiles (CSV) Values at full stored precision; tables on this site may round for display. Licensed under CC BY 4.0.
Population Distribution
Serum bicarbonate, reported as total carbon dioxide on most chemistry panels, represents the metabolic component of acid-base balance. It is regulated by renal bicarbonate handling and respiratory CO2 elimination. These percentiles describe the full US adult population from NHANES 2017-March 2020 rather than a screened healthy subgroup. Values are reported as mmol/L (equivalent to mEq/L for a monovalent anion).
Frequently Asked Questions
Is this bicarbonate or total CO2?
Most chemistry panels report total CO2, which includes dissolved CO2 and carbonic acid but is dominated by bicarbonate. The two are used interchangeably in routine chemistry.
Why does bicarbonate shift with age?
Older adults more often have mild chronic kidney dysfunction, respiratory changes, and medication effects that produce subtle acid-base shifts. That slightly broadens the distribution.
How does this relate to the anion gap?
The anion gap is calculated from sodium, chloride, and bicarbonate. Bicarbonate is the main buffer anion and its level shapes the gap along with chloride.
Data Sources
Cite this data
LabNorms. Bicarbonate population percentiles by age and sex. Data: NHANES 2017-March 2020 Pre-Pandemic. https://labnorms.com/analytes/bicarbonate/. Licensed under CC BY 4.0. Accessed [date].
Download Bicarbonate percentiles (CSV) Values at full stored precision; tables on this site may round for display. Licensed under CC BY 4.0.