It's one of healthcare's greatest bargains: Nearly 88 percent of prescriptions written in the U.S. in 2014 were for knock-offs of brand-name drugs, sold at a fraction of the price. And for the most part, consumers don't lose anything in the deal. "Even though generics aren't perfect replicas, the FDA is really on top of evaluating them and ensuring that the ones it approves have the same active ingredients and absorb in the bloodstream just as if a person were taking the brand name," says Mario Rocci, PhD, president of the American Society for Clinical Pharmacology and Therapeutics. Three things you should do before filling your next prescription:

Gauge the grade.
You may be surprised to learn that the FDA labels every copycat drug either A or B, depending on whether it releases active ingredients at the same rate and levels as the brand name (A) or at different rates or levels (B). If a drug enters your bloodstream too slowly or too quickly, it may cause side effects or prove ineffective, requiring your doctor to adjust your dose. While it's uncommon that you'll be prescribed a B drug, your pharmacist can tell you the rating of meds you're taking.

Look for undisclosed side effects.
Some medication side effects don't become apparent until a drug has been on the market for a few years, at which point the sheer number of people who have taken it can lead to the discovery of issues not present during a clinical trial. "If a brand-name drugmaker discovers a new side effect and wants to add it to the label, they can do so immediately," says Rocci. Generic manufacturers don't have that freedom; their drug's packaging info can't be altered in any way that's different from the original brand name, even if they learn of side effects. Print out the package insert for the brand-name drug online and compare it with your generic Rx.

Read the ingredient list.
Since the active ingredients in generic and brand-name drugs must remain the same, the biggest variables are inactive substances such as binders, fillers, flavors, and dyes used to keep a pill together or distinguish it from other meds. "An adverse reaction to a drug may be the result of an allergy to one of those components," says Stephen Schondelmeyer, PhD, professor and head of pharmaceutical care and health systems at the University of Minnesota College of Pharmacy. Tell your doctor and pharmacist if you're allergic to any ingredients, like sulfites, gluten, or Yellow 5, that may be in your medication.

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