I had inflammation in both lungs when i had covid. i did a ct scan and they gave me dexamethasone for 6 days. but they said to wait 3-4 months to do another ct scan. does that mean the inflammation takes that long to go away?

Inflammation usually clears more quickly, but CT scan abnormalities may persist several weeks. Repeat CT at 3-4 months sounds Fien. If you remain uncertain, ask your doctor.

The time allowed should be enough for acute changes to return to normal and check for structural recovery of the lung parenchyma or tissue. It does not mean acute inflammation will take that long.