After surgery, my lip has swollen to 4 or 5 times its normal size. Is this normal or should I consider ER treatment?

Swelling after any surgical procedure is to be expected.  Loose areas like the lips or around the eyes often exhibit a great deal of swelling during the first few days.  If the swelling continues and if there is a great deal of discoloration or bruising, it might be advisable to have your physician examine the area to insure the swelling is not due to excessive bleeding.   Fortunately, this is very uncommon.

Swelling from Mohs is very normal. It can be frightening to patients how much an area will swell, but remember that during the procedure a lot was done to keep excess blood flow from that area, so when it starts again, it's quite frequent to have a lot of swelling. I don't think you need to go to the ER, and I don't think they can really help. Ice it, make sure to keep your head elevated. "This answer has been solicited without seeing this patient and
cannot be held as true medical advice, but only opinion. Seek in-person
treatment with a trained medical professional for appropriate care."