Yes, protein powder can expire. The date on the container is usually more about quality than a sudden safety cutoff, but the powder may lose freshness, flavor, texture, and some nutritional value over time.
How long it stays good depends a lot on storage. Heat, humidity, and exposure to air can make protein powder clump, change color, smell off, or taste stale. Whey protein stored in warmer conditions has been shown to break down faster, especially in quality and appearance.
A sealed container kept in a cool, dry place may last longer than one kept near heat or moisture. Once opened, it is best to keep the lid tightly closed and avoid using a wet scoop, since moisture can increase the chance of spoilage.
Do not use protein powder if it smells rancid, has mold, unusual discoloration, major clumping, or a strange taste. When in doubt, throw it out. Anyone with kidney disease, digestive concerns, pregnancy-related questions, or a need for higher protein intake should speak with a doctor or registered dietitian before using supplements regularly.