How long should u wait to take 3yr old to dr. who has a fever and paleness in face, but no other symptoms of illness?

Depends on fever: In my opinion, a child this age should be checked by a doctor if the temperature is over 101. F. Even if there are no other symptoms that are apparent. For example, girls this age can have a urinary tract infection that isn't obvious except for fever. If your child is not acting sick and appetite is ok, you can wait until office hours, but i would not delay longer.

It depends: If he has been seen regularly for well-child visits and has no chronic illness, this may soon pass (likely a viral illness) without problems. If he/she is eating and sleeping well, then less much of a worry. If he does have significant medical problems and taking medications, you may want to keep close eyes on him and consult your doc at your earliest convenience.. Good luck..