Healthsource: Using online pharmacies for pet medications

UNDATED In fact, any pet medicine can be expensive, but the FDA is warning pet owners to be very careful about using online pharmacies.

If you search 'heartworm meds' on the Internet, you may overwhelmed as many sites offer big savings.

"If it's the actual product. The problem is a lot of online pharmacies are not selling legitimate product," said Dr. Scott Liggett of Flushing Animal Hospital.

Liggett says the FDA is sending out warnings in hopes of alerting pet owners to beware because fake pet medicines are everywhere.

"Even some major chains are selling product that isn't actual product," Liggett said.

So if you are not buying from your vet, how do you know heart worm preventive or any pet medicine is coming from a legitimate source?

"If you are buying a heartworm product and they allow you to purchase it without a prescription, it is not a legitimate pharmacy. All heartworm products are prescription products," Liggett said.

You want to look for a stamp of approval from Vet VIPPS or Veterinary-Verified Internet Pharmacy Practice Sites.

"You just have to be careful that price is not your only criteria. Safety and effectiveness should be important to you," Liggett said.

It is also critical to have your pet screened for heartworm every year, even if you are giving them preventative meds.

"Nothing is 100 percent and recently in the South there are starting to be reports of heartworms that are resistant to the current drugs and with a lot of these animals being shipped north via various aid agencies, it will probably get here sooner or later," Liggett said.

April through November is when most people give the heartworm preventative, but some pet owners are doing it year-round. Liggett says that isn't a bad idea, because it also protects pets' families as there are some worms that can be spread to humans, too.