Do Antibiotics Expire?

Antibiotics are medications designed to treat various types of bacterial infections and can be taken as an ointment, injection, or in liquid or pill form (via MedlinePlus). There are well over 100 types of antibiotics that fall into seven classes and are effective for specific types of infection, such as pneumonia, strep throat, or urinary tract infection. Some commonly prescribed antibiotics include amoxicillin, cephalexin, and tetracycline (per eMedicineHealth).  

Just like any other medication, antibiotics are not without possible side effects, including nausea, rash, diarrhea, and yeast infection. In rare cases, antibiotics may induce allergic reactions, lead to antibiotic-resistant infections, or result in colon damage (via MedlinePlus). 

It's important to take antibiotics exactly as prescribed. A full round of antibiotics should always be completed as instructed by your doctor to prevent reinfection from lingering bacteria (via MedlinePlus). In doing so, you shouldn't wind up with any leftover doses (via Insider). However, if leftover antibiotics are hiding in your medicine cabinet, should you assume they've expired by a certain date?

According to the Rx savings program, Prescription Hope, "An [expiration] date is a point at which the drug manufacturers have tested the potency, efficacy, and safety of the medication towards a relevant health condition." Research has found that many over-the-counter (OTC) medications, as well as prescription drugs, maintain potency for several years after the labeled expiration date (via Insider). But does this apply to antibiotics? 

According to Prescription Hope, 90% of the potency and efficacy of antibiotics in pill form holds for five years past the expiration date, with proper storage. But this shouldn't encourage you to keep any unused antibiotics. "Almost all antibiotics are prescribed for a full course, and therefore there should not be any leftovers," a clinical adviser at digital-health startup Medzino, Dr. Kim Langdon, told Insider, noting one exception: "In the case of daily or chronic use, one year from dispensing is the safe expiration date."

Taking leftover antibiotics to treat a condition without consulting a doctor is risky because you might be taking the wrong medication if you don't have a bacterial infection. Not only that but self-administering expired antibiotics can be toxic (per Prescription Hope). Overloading your system with antibiotics can kill off your body's good bacteria, leading to gastrointestinal issues or a severe case of C. difficile infection. If you are taking other medication or have been diagnosed with a medical condition since you were last prescribed antibiotics, there could be potentially risky drug interactions or side effects impacting your health.