Is fainting after breast reduction normal?

Fainting after surgery is not necessarily "normal"; there are variety of "reasons" why this may be occurring.  It is important that you communicate post op concerns/questions directly with your plastic surgeon who will be in best position to advise you.   Given these occurrences, make sure that you have support around you at all times.  Best wishes.

Fainting after any type of surgery is not a common side effect and may
be caused by a variety of reasons. It could be something easily fixed by stopping medications, making sure your post-surgical diet is healthy and supporting good hydration but always report issues such as the ones your having directly to your plastic surgeon who would be the best to advise you. It is appropriate to have soreness after breast reduction surgery and recovery time averages 2-4 weeks, depending on grams removed, if drains were placed, and the overall health of the patient.
You do need to contact your plastic surgery and make them aware of you concerns.
Wishing you the best.

Your question is a valid one and it should be acted upon quickly.  There are many reasons you maybe fainting but to tell you why in this forum is not wise and I would recommend you see your surgeon as soon as possible to determine the cause.  It may be something simple as not keeping hydrated to a more serious reason.  Recovery can take up to two weeks to feel like you are on your game again. You may be doing too much and need to slow down but all these issues need to be discussed with your surgeon.