I worked in pharma for over a decade, had lots of conversations with the chemists about things like generics vs name brands and expiration dates. TLDR: generics are required by the FDA to be identical to the "branded" versions or they are not allowed to be sold. Expiration Dates are the last date that a medication is expected to have 100% efficacy when stored under the worst possible conditions. So, if you keep your bottle of pills on the windowsill in direct sunlight in humid FL your pills should still be ok up until that date. Now, if you store your stuff in a less idiotic way, it can be good for much longer, potentially decades. Also medications are only allowed to degrade in a way that reduces efficacy, they're not allowed to turn into something else. So that 10yr old expired pill might only give you 95% the effect of a fresh one, but it's not going to turn into poison either. The US Army looked into this and drew similar conclusions and now uses rather than discards "expired" meds and has saved millions of dollars thanks to this policy change (look it up). FWIW