Is it safe to use vitamins after the expiration date?

It depends...: Expiration dates tend to be rather artificial & somewhat arbitrary. If a vitamin has an expiration date a year after manufacture it is not like the next day it suddenly goes bad. They may lose some potency over time but are unlikely to be dangerous. A vitamin a month or 2 past expiration date is probably ok- if it expired 2 years ago i would be more cautious!