Does hyperventilation cause lower CO2 results in a blood test?

Hyperventilation can indeed affect your blood CO2 levels. When you hyperventilate, you exhale more carbon dioxide than usual, which can lead to a temporary decrease in CO2 levels in your blood. This is because hyperventilation causes a state known as respiratory alkalosis, where the blood becomes less acidic due to the reduced CO2.

In your case, the anxiety and heavy breathing during the blood draw could have contributed to the slightly lower CO2 level you observed in your lab results. If your CO2 level was only slightly below the reference range and you were experiencing significant anxiety during the test, it's likely that this was a temporary effect.

However, if you continue to have concerns or if you experience any symptoms, it would be wise to discuss this with your healthcare provider. They can assess whether further investigation is necessary and provide reassurance or additional guidance based on your overall health and medical history.