I had left an open vitamin bottle (High potency. Multi Guard) in the drawer two or three months ago. I have taken them again, I guess there is no problem. Do they hold in good open condition for a few months?
In LAMBERTS® products, the expiration date suggested on the label indicates that from the same date the product begins to lose the potency indicated on the label, either in milligrams or international units, but not that it is harmful (provided that has been stored as directed on the label).
If the product that you refer to, even if it has been open, is not expired, and has been stored correctly, there is no problem with the effectiveness of the content and you may take it.