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pCO2

Blood gases · also printed as PCO2, PaCO2, pCO2 (arterial), pCO2 (venous), PvCO2

Typical UK adult range4.7 to 6.0 kPa

Ranges vary between laboratories; the range printed on the report takes precedence.

What this test measures

pCO2 is the pressure of carbon dioxide dissolved in the blood. It shows how well the lungs are clearing carbon dioxide, and it moves with breathing rate.

Why doctors request it

Part of every blood gas, used in breathing difficulty, lung disease and when oxygen is being given.

What commonly pushes it up

Under-breathing from sedation or muscle weakness
Long-term lung disease such as COPD
Severe asthma when tiring

What commonly pushes it down

Over-breathing from anxiety, pain or fever
The body compensating for an acid load
Pregnancy, slightly

Everyday reasons for a value outside the range

Venous values run about 0.8 kPa higher than arterial
Units differ (kPa in the UK, mmHg elsewhere)

About the sample

Arterial or venous; the report should say which.

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

Got a report with pCO2 on it?

Upload a photo or PDF and see every line against the range your lab printed, explained in plain English. First report free.

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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.