---
title: "What does a high Carbon Dioxide mean?"
type: biomarker-interpretation
url: "https://www.test-well.com/biomarkers/carbon-dioxide/high"
biomarker: Carbon Dioxide
direction: high
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 high Carbon Dioxide mean?

> Serum CO2 on a metabolic panel is mostly bicarbonate. A high value means metabolic alkalosis or compensation for chronic lung disease: vomiting, diuretics, low potassium, excess antacids or baking soda, and COPD or sleep apnea raising CO2 retention. Mild elevations are common with diuretics and rarely matter; larger ones are read with potassium, chloride and the clinical picture.


## What is the normal range for Carbon Dioxide?

- age 18+: 22.0 – 29.0 mmol/L



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

1. Thiazide or loop diuretics
2. Vomiting or nasogastric losses, low potassium
3. Chronic lung disease with CO2 retention, severe sleep apnea
4. Excess antacid or bicarbonate intake
5. Cushing's syndrome, hyperaldosteronism

## What symptoms go with high Carbon Dioxide?

- Usually none
- Muscle cramps, twitching, lightheadedness when marked

## What do clinicians usually check next?

- Potassium, chloride, sodium (the anion gap), kidney function
- Medication review
- Blood gases and lung evaluation if lung disease is suspected

## 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

### Is a CO2 of 31 a concern?

Rarely — it is a common finding on diuretics or after vomiting. Persistent values above ~32 with low potassium warrant a look at the cause.

## Related

- [What does a low Carbon Dioxide mean?](https://www.test-well.com/biomarkers/carbon-dioxide/low)
- [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/high
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.