Typically, protein powder expires a year after manufacturing. That said, the variety of protein powder on the market is vast, and the expiration date and longevity of the supplement varies by manufacturer. For maximum results, it is recommended that people consume protein powder as soon as possible after opening and search for the expiration date before purchasing.
As with vitamins and other supplements, the potency of protein powder inevitably decreases over time. Regardless, it still is a popular supplement for weight loss, strength training or for people just looking to add protein to their dietary regimen. Ideal storage for any protein powder includes placing it in an airtight container and in dry conditions for maximum efficacy. It is especially important that any protein powder be kept dry, as contact with moisture decreases the potency of the product and renders it unusable.