When you're taking any sort of prescription medication, or you're using a product that's been issued to you by prescription, it's always important that you check the expiration date. This is important before you purchase the product, as well as if you're using it again long after you purchased it. The expiration date will usually be listed somewhere on the label. The amount of time it takes for a prescription product to lose its potency and effectiveness can vary. Some drugs lose their potency after months or years, while others--such as antibiotics--may be unusable after ten days. If you see on the label that a product has expired, you should throw it away. When refilling a prescription it's important to make sure the prescription itself hasn't expired. Many prescriptions become invalid a year after they're issued; others, after only a few months. If you have any questions, contact a healthcare professional, or ask a pharmacist.