Transcript for Is Your Veterinarian Being Honest With You?

Reporter: Say hello to maeby. This lovable mutt is coming to visit us at abc news headquarters for a very special assignment. Hey, welcome to abc. Thank you. We're excited to be here. Reporter: We're going to make maeby a star. No, not that kind of star. We're sending this brave 5-year old pooch undercover into a place dogs fear the most -- the veterinary clinic. We wanted to find out if what this man says about the veterinary business is true -- that some vets, out to make a buck, sell unnecessary shots, tests and procedures to unsuspecting pet owners. I'm clearly not making friends within the veterinarian industry. But I feel I'm saying things that need to be said that aren't being said. Reporter: Andrew jones worked as a vet for 17 years until he quit the industry after a dispute with his medical board over marketing issues. He's now revealing what he calls veterinary secrets online. As a young veterinarian in british columbia working at a clinic, jones says he got an early lesson about upselling after telling a pet owner just to monitor a lump on their dog. Jones says the clinic owner quickly clued him in on the effectiveness of using the dreaded "c" word. The practice owner said, no, that's not how you do it. What you need to do is get that dog back in. Reporter: And what did he tell that pet owner? He said that it might be cancer. And it's usually the "c" word -- pet owners get really concerned. Reporter: Was it cancer? No, it was a benign fatty tumor. Reporter: Throughout his career, jones says he discovered a dark reality about some veterinarians in the u.S. And canada, including himself. They feel that pressure of, I've got these overhead costs to make, and that's where your judgment gets clouded. Reporter: Jones says under pressure from bosses, he ordered services that were not needed. Did you feel that you might get fired if you didn't do that? No question. And, if I didn't meet this certain target, then yeah, my employment was at threat. Reporter: But jones tells us even when he owned his own clinic, he, at times, continued upselling, admitting to using the teeth-cleaning come-on. So for instance, seeing a dog that has a little bit of tartar, then I might say, I think your dog should have a dental cleaning. It's obviously more profitable for the practice. Reporter: Do vets really push unneeded services as jones claims? Well, that brings us back to our undercover canine, maeby. We decide to send a healthy dog -- which maeby certainly appears to be -- into vet clinics to see what tests and treatments are recommended. To make sure that maeby is in good shape, her owner, katrina, takes her to this manhattan clinic for a thorough checkup with a well-respected vet. Hello, sweetie. Her teeth are very clean and i can tell that you're paying some attention to keeping her teeth clean. Reporter: According to dr. Rebecca campbell, maeby is completely healthy. So we send her undercover into vet clinics for a routine exam. Most of the places found that maeby is just fine. Except for a tiny bit o tartar, I think she's good. But check out what we heard during an exam at this clinic in new jersey. Reporter: The vet takes a quick look at maeby's teeth. There's a little bit of tartar buildup back there. And you can't brush it back there. Reporter: After the owner asks what she should do, the vet recommends an annual teeth cleaning -- for dogs that means going under general anesthesia. I mean, she could have a lot worse stuff going on, and I'd never see it unless she was under anesthesia. Reporter: The clinic later gives us maeby's exam report which indicates she has dental disease. The cost of that recommended teeth cleaning under general anesthesia -- $250. You say dentistry is the up-sell. It is the big up-sell. VERY MUCH, ON the McDonald's equation of, would you like fries with that? Reporter: The vet later stood by her advice, saying that larger dogs over the age of four can benefit from a cleaning and risks posed by anesthesia are minimal. For another perspective, we turn to dr. Marty becker, one of the country's leading experts in veterinary care. I wouldn't recommend the cleaning unless it needed it. If it does not have periodontal disease, there's no use putting it through the risk of anesthesia. Reporter: Because doing things that a dog doesn't need can be dangerous. Absolutely can be dangerous. Reporter: Another big ticket item on vet bills are vaccination costs. And jones says some vets can be quick when it comes to pushing the shots. Every year, pet owners get those reminder cards that their animals are due for a vaccination. But what many vets apparently fail to disclose is that according to the latest guidelines, most of the required vaccines only need to be given once every three years. A lot of people are still into giving them every year, but that is not the recommended protocol by the american veterinary medical association. Reporter: To find out what vets recommend about vaccinations, we bring in another undercover dog, a five-year old pitbull mix named honey. Her owner, alison, says honey's up to date on all of her vaccines. Reporter: But without even asking about honey's vaccination status, this vet orders up a regimen of shots. Did you bring the shots in? She's getting shots? Reporter: Shots? D reminthe vet this is just a checkup. Oh, okay. I was told annuals. Okay. When were we last vaccinated? It was two years ago. She had rabies and distemper. Okay. I think she's okay. Distemper is typically an annual vaccine. Reporter: But industry guidelines say the vaccine for distemper, a viral disease, is good for three years. The clinic later told us that a vet's individual judgment is just as important. So what else happened with our pretty pitbull, who was checked out as being in good shape? Well, honey also received a finding of dental disease from a clinic and a recommendation for a $300 teeth cleaning under general anesthetic. So, you would definitely recommend a dental cleaning? Definitely recommend it. Reporter: When we later called the clinic, nobody would answer our questions about the proposed treatment. In the end, both of our undercover dog owners could have incurred hundreds of dollars for potentially unnecessary treatments. Jones says what ultimately drives pet owners to pay up is their deep love for their animals. Do you think some vets take advantage of pet owners who just really don't know any better? Of course. Because you can. I mean, because you're preying on their emotion. Reporter: When we asked the industry association about upselling allegations, they said it's up to pet owners to decide whether to follow a vet's recommendation. At the end of the day, jones says the vast majority of vets are ethical and try to do the right thing. Still, he says pet owners need to walk into a clinic with their eyes wide open. They're not just going to a veterinarian clinic, they're going to a business. So start to really question stuff that is recommended or advised. And you really can take charge of your own pet's health.

This transcript has been automatically generated and may not be 100% accurate.