Generic drugs 101: what FDA equivalence actually guarantees

Generics use the same active ingredient, same strength, same route of administration, and must demonstrate bioequivalence within FDA's 80-125% AUC window.

Inactive ingredients (binders, dyes, fillers) can differ. This matters in rare cases — patients with celiac disease, dye allergies, or narrow-therapeutic-index drugs (warfarin, levothyroxine, lithium) sometimes do better on a specific manufacturer.

If you switch generics and feel different: ask your pharmacist which manufacturer filled it, and request the previous one next time.