If your doctor thinks that you have hypercapnia, they’ll likely test your blood and breathing to diagnose the issue and the underlying cause.
An arterial blood gas test is commonly used to diagnose hypercapnia. This test can assess the levels of oxygen and CO2 in your blood and make sure your oxygen pressure is normal.
Your doctor may also test your breathing using spirometry. In this test, you breathe forcefully into a tube. An attached spirometer measures how much air your lungs contain and how forcefully you can blow.
X-rays or CT scans of your lungs can also help your doctor see if you have emphysema or other related lung conditions.