Many popular prescription drugs are being counterfeited and distributed to consumers through online pharmacies, mail-order services and cross-border purchasing. These look-alike medications pose significant health risks, as key ingredients may be absent, diluted or poisonous.

To avoid purchasing counterfeit medications, follow these tips.

Use caution when shopping online for medicines. Approved online pharmacies should display the “VIPPS” seal, shown here. The seal should link you to the National Association of Boards of Pharmacy Web site (http://www.nabp.net), where you can view information about the pharmacy or search for other approved pharmacies. Sites without the VIPPS seal may be selling counterfeit products.

Avoid purchasing drugs outside the U.S. border. Because of safety concerns, federa agencies prohibit individuals from importing prescription drugs into the United States in most cases. In Mexico, for example, counterfeit drugs account for 25 percent of medications, according to the U.S. Department of State.

Pay attention to pill appearance and packaging. If you notice any changes in pill size, shape, texture, color or taste from a previous prescription, discuss it with your doctor or pharmacist. In addition, examine the medication packaging. Hazy lettering, flat printing (rather than raised printing), and missing expiration dates or lot numbers are clues that a medication may be counterfeit.

Report suspicious medications. If you think you have received a counterfeit medication, don't use it. Return the drug to the pharmacy that gave it to you, or contact your physician or the manufacturer.