We've advised you about the process behind determining expiration dates for drugs. It turns out that the "expiration" date may not mean very much. It just indicates that the manufacturer is willing to guarantee that the drug will still be potent until that date. Many drugs last a lot longer — but the manufacturer either isn't willing to bother testing the drug to see if it will last longer, or simply hopes you'll toss the product when you see it's "expired" and go buy a new one.
Some have asked whether this information applies to supplements. The answer is "it depends."
For instance, probiotics degrade quickly after their expiration date. So, you'll want to use them or replace them by their expiration date, or they may not do you much good. They won't hurt you, but they may not help you, either.
Herbs and herbal extracts are similar. They become less potent over time. And it's probably best to start fresh once a herb-based product reaches its expiration date.
With vitamins and minerals, however, you likely have more wiggle room. Many vitamins and minerals don't degrade at all, so they can be potent indefinitely.