SAN FRANCISCO — Michael Fasman’s 12-year-old dog, Hudson, limps from pain caused by arthritis and an amputated toe, but Fasman doesn’t want to give her painkillers because “they just knock her out.”

So the San Francisco resident has turned to an alternative medicine that many humans use to treat their own pain and illness: marijuana.

On a recent morning, Fasman squeezed several drops of a cannabis extract onto a plate of yogurt, which the Portuguese water dog lapped up in seconds. It’s become part of Hudson’s daily routine.

“We think it’s really lifted her spirits and made her a happier dog,” Fasman said. “It’s not that she’s changed. She’s just back to her good old self.”

As more states legalize marijuana for humans, more pet owners are giving their furry companions cannabis-based extracts, ointments and edibles marketed to treat everything from arthritis and anxiety to seizures and cancer.

Most of these pet products, which aren’t regulated, contain cannabidiol or CBD, a chemical compound found in cannabis that doesn’t get pets or humans high. They contain little or no tetrahydrocannabinol or THC.

But veterinarians say there isn’t enough scientific data to show cannabis is safe and effective for treating animals. Although medical marijuana is legal in 28 states, it remains illegal under federal law, so there has been relatively little research into benefits for humans or animals.

Veterinarians in California and other states are legally barred from prescribing or recommending cannabis. They risk losing their licenses if they do.

“Our hands really are tied,” said Ken Pawlowski, president of the California Veterinary Medical Association. “Definitely we’re getting more questions from clients asking about it for their pets, but unfortunately we don’t have any answers for them.”

Karl Jandrey, a veterinarian who teaches at the University of California, Davis, said he tells his clients they “use them at their own risk with the potential to spend money for no improvement, or a risk of adverse side effects.”