General care & prescription savings
Generic drugs 101: what FDA equivalence actually guarantees
By BetterBuyRx Editorial Team · April 20, 2026 · 4 min read
This article was editorially reviewed for sourcing and clarity. It has not been medically reviewed by a clinician.
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.
Last updated: 2026-04-20. Educational information only; not medical advice. This information is not a substitute for care from a licensed health professional. If you may be having a medical emergency, call 911 or seek emergency care. Prices are estimates and vary by pharmacy, location, quantity, and eligibility.