It can work well for many conditions. But there are also other drugs and treatments that have been studied more thoroughly. If you’re using it to calm down your cat, I don’t see the harm in giving it a try. But if you’re using it for more serious conditions, you might want to verify there aren’t more proven effective treatments out there.
One other caution about hemp oil, the main drug component of it, CBD, is very safe on its own. But I would exercise caution (and do a Google search if your vet can’t talk about it) with adding CBD to other medications. Steroids in particular are detoxified by the same liver enzymes as CBD making it potentially slower to clear steroids from the body when also taking CBD. I don’t recommend mixing steroids and CBD.
CBD products can affect how other meds are absorbed into the body as well and if there are other medications being used, either ask the vet or check out some sources yourself.
I have oil and capsules on hand and frankly am underwhelmed by the results. Others have had different experiences though.
I do give one of my guys 2 drops of CBD oil (hemp) everyday for anxiety. If I forget, I feel like I can tell the difference by the way he acts. Could be my imagination, but I don't think so. If he has to go in for a dental or anything like that though, I stop using it for at least a week just to make sure there are no complications. That's just me being overly paranoid