Diffusing Capacity for Carbon Monoxide (DLCO)
- Sample Type
- Standard
- Fasting
- No
- Unit
- mL/min/mmHg
The DLCO test measures the ability of the lungs to transfer gas from inhaled air to the red blood cells in the pulmonary capillaries. It is a critical component of a Pulmonary Function Test (PFT) because it assesses the integrity of the alveolar-capillary membrane. It depends on three factors: the total surface area available for gas exchange, the thickness of the membrane, and the volume of blood (hemoglobin) in the pulmonary capillaries. It is often corrected for alveolar volume (DLCO/VA) to differentiate between intrinsic lung disease and restrictive patterns caused by extrapulmonary factors.
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Enter your lab result to see where you stand compared to the standard reference range.
Why Context Matters
DLCO results are highly sensitive to hemoglobin levels; anemia will falsely lower the value while polycythemia will falsely raise it. Smoking within 24 hours (CO-Hb levels) can also interfere. A second opinion is often needed to distinguish between emphysema, interstitial lung disease, and pulmonary vascular disease when spirometry alone is inconclusive.
Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.
Clinical References
Source-of-truth databases and clinical guidelines for Diffusing Capacity for Carbon Monoxide (DLCO):
Official Sources
- Interstitial Lung Disease in 2025—Progress, Challenges, and Hope Ahead - PMCpmc.ncbi.nlm.nih.gov
- Interstitial Lung Disease Clinical Practice Guidelinesrheumatology.org
Research & Guidelines
Related Indicators
Medically Reviewed by Dr. Binoy Babu, MBBS
Board Certified Doctor • 10+ Years Clinical Experience
Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.
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