---
title: "What does a low Carbon Dioxide mean?"
type: biomarker-interpretation
url: "https://www.test-well.com/biomarkers/carbon-dioxide/low"
biomarker: Carbon Dioxide
direction: low
reference_range:
  - "age 18+: 22.0 – 29.0 mmol/L"
reviewed_at: 2026-09-06
review_status: reviewed
date_published: 2026-09-05
---

# What does a low Carbon Dioxide mean?

> Low serum CO2 (bicarbonate) means acid is accumulating or bicarbonate is being lost: uncontrolled diabetes, kidney disease, diarrhea, some medications (acetazolamide, topiramate, metformin in rare cases), heavy exercise or alcohol, and toxic ingestions. Hyperventilation from anxiety also lowers it. The anion gap and glucose decide how urgent it is.


## When does this result need same-day care?

- CO2 below ~15 mmol/L, or a low value with vomiting, deep rapid breathing or confusion — emergency care

## What is the normal range for Carbon Dioxide?

- age 18+: 22.0 – 29.0 mmol/L



## What are the common causes of low Carbon Dioxide?

1. Diabetic ketoacidosis, starvation or alcoholic ketosis
2. Chronic kidney disease, renal tubular acidosis
3. Severe diarrhea
4. Medications: acetazolamide, topiramate, high-dose aspirin
5. Lactic acidosis from sepsis or severe illness; toxic alcohols
6. Chronic hyperventilation, under-filled tube (mild false low)

## What symptoms go with low Carbon Dioxide?

- Rapid breathing, nausea, fatigue, confusion when significant
- Often none when mild

## What do clinicians usually check next?

- Glucose, kidney function, potassium, chloride (anion gap); lactate if unwell
- Medication review
- Urine studies for renal tubular acidosis when persistent

Follow-up tests at TestWell: [Glucose](https://www.test-well.com/tests/glucose-basic) ($14.99).

## How do you recheck Carbon Dioxide?

| Test or panel | Type | Price | Fasting | Results |
| --- | --- | --- | --- | --- |
| [Basic Metabolic Panel](https://www.test-well.com/tests/basic-metabolic-panel) | Test | $20.99 | Yes | 1–3 business days |

Plus one $6 lab processing fee per order; physician authorization included.

## Common questions

### Can anxiety lower my CO2 on a blood test?

Yes — sustained fast breathing blows off CO2 and the bicarbonate falls a little to compensate. That pattern is mild and harmless; large drops need a metabolic explanation.

## Related

- [What does a high Carbon Dioxide mean?](https://www.test-well.com/biomarkers/carbon-dioxide/high)
- [Carbon Dioxide reference ranges](https://www.test-well.com/biomarkers/carbon-dioxide)
- [Glucose reference range](https://www.test-well.com/biomarkers/glucose)
- [Creatinine reference range](https://www.test-well.com/biomarkers/creatinine)
- [eGFR reference range](https://www.test-well.com/biomarkers/egfr)

## Sources

- [Mayo Clinic Labs](https://www.mayocliniclabs.com/test-catalog/overview/8434)

---

Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-06. Review policy: https://www.test-well.com/editorial-policy

Canonical page: https://www.test-well.com/biomarkers/carbon-dioxide/low
Machine-readable catalog: https://www.test-well.com/api/catalog.json · MCP server: https://www.test-well.com/mcp · Overview for agents: https://www.test-well.com/llms.txt

Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.