Many of us may not take expiration dates on pill bottles too seriously. But experts warn against taking expired drugs. The reason is simple: the Food and Drug Administration and the drug companies really don't know what happens to outdated medications. “The drug could retain its potency,” says FDA spokeswoman Shelly Burgess. “The drug could degrade into nontoxic impurities, giving rise to an ineffective product, or the drug could degrade into toxic impurities.” So pretty much anything at all, then. An FDA study in 2006 showed that 88% of drugs had a “one year beyond their original expiration date” shelf life—if stored properly. However by the time drugs get into your hands, they've often weathered some challenging environments. “Medication that the average person buys can go through many hands from the time it is shipped from the manufacturer until it reaches the end-user,” says Desmond Hunt, a senior scientific liaison for the US Pharmacopeia. “During each handoff and during the transportation process, there is a potential for a drug product to be stored outside its labeled temperature requirements. It could sit on the tarmac in humidity, for example, or sit out in the rain.” Because of this, the FDA doesn't recommend swallowing even recently-expired medication.