Can I deduct round-trip medical miles if I go to a doctors appointment on my way home from work? Or do I need to subtract my normal commuting miles?

Say I live in Hometown and work in Otherville. I normally commute about 10 miles each way every day. However, if I have a doctor's appointment in Another City (which is 20 miles from both Hometown and Otherville) and I leave straight from work to go there, then going straight home afterwards, can I deduct the entire round-trip or does part of it still count as my commute?

posted