Mykos out of date , Can it stil be used?

Should last 20 years if stored properly, "use by" dates are mainly for stock control. If it is only out of date recently, use it with complete confidence, there is no magic ingredient that will neutralize a product overnight.

The dates are on the products are for freshness and to make the labels advertised CFU counts accurate if it was store properly. It will still be fine, just might not be as strong as the label is listing, can always use a bit more. When I worked for a company that had probiotics, they would find fresh off the line they had 3-5x times the advertised amounts, however by the time they hit their expiry/best before date they where down to the numbers on the box. In short use it up, won't go bad if its store right. not like rot and perishable food.

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if its in dry, i would not worry. maybe not so active, but if storing was right, its should be still potent.

If stored properly it should still be fine. Maybe won’t be as effective as it was when it was new but it doesn’t mean it’s completely gone bad. But if it worries you, get some fresh stuff for piece of mind.