How do I tell if Protein Powder is bad?

When protein powder goes bad it can change color, clump, take on an odour and will taste different. This is especially the case if it is not kept in an airtight container and is exposed to moisture. Exposure to moisture can cause protein powder to go off very quickly. If you’re unsure if protein powder is still good, you can taste a small amount. If it tastes like cardboard then it has likely got bad and should be thrown out.