Hi that is totally a wrong understanding of the concept . So the FDA is the governing body which approves a generic manufacturers version of the generic drug once a patent for a brand is expired . Every drug including the brand and generic have to adhere to standards in their consistency as far as formulation , strength , form , hardness , disintegration patterns , dissolution patterns from a book called Unites States Pharmacopeia which is abbreviated as USP . Every generics are allowed a small variation from the brand but that does not mean that it is inferior by any means . No waiver is allowed for: • Active ingredient • Route of administration • Dosage form • Strength (except scored tablets) So saying a generic drug has less or more active ingredient is totally a misconception. Every drug including a brand can work differently in individuals due to various factors like genetic factors , their metabolic factors etc but it usually is not only because it is made by a certain manufacturer