Preserve Mac Forte Advanced comes marked with a suggested "best used by date." This date is a suggestion and by no means does the product become ineffective just because it reaches this date. Sometimes customers find a bottle that is a couple months past the recommended date or even many months beyond the date. It is still safe to take the product and it is still effective. If you have a bottle that is 2 years beyond the date or more, then it has probably lost some of its effectiveness and we recommend you get a new bottle.