Postponing your interview is the better option it is less hassle and in the end your visa will be issued faster. If you go to your interview now and delay the medical exam you will get a 221g be under “refused” wait to do your medical exam, you need to do your medical exam, get your medical results and turn them into the embassy this can also be a delay depending on the clinic everywhere is different, wait until the medical exam is entered into your case, case has to turn into ready then approved and then issued all this can turn into an estimate 1 month to 60 day wait (worse case scenario this is what the embassy says) or even less after turning in your medical exam. Now let’s say you delay the interview the 2 months and you’re approved the embassy is issuing visas within 2 weeks you get your visa.