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Gas transfer (TLCO)

Breathing tests · also printed as TLCO, DLCO, Transfer factor, Gas transfer, TLco

Typical UK adult rangeNo single typical range

No fixed range; compare with the printed predicted value and percent predicted.

What this test measures

TLCO measures how well gas crosses from the air sacs into the blood, using a tiny amount of carbon monoxide. It reflects the lung's working surface and its blood supply.

Why doctors request it

Used in lung fibrosis, emphysema, some heart conditions and before some treatments that can affect the lungs.

What commonly pushes it up

Asthma, sometimes
Bleeding into the lungs
Lying flat, and a high haemoglobin

What commonly pushes it down

Emphysema
Lung fibrosis
Lung clots and other circulation problems in the lung
Anaemia, which the lab corrects for
Smoking on the day

Everyday reasons for a value outside the range

Anaemia lowers it, so a haemoglobin-corrected value is often printed
Smoking within hours lowers it
Predicted values depend on age, sex and height

About the sample

No smoking for 24 hours beforehand where possible.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.

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This is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.