I think my cat has a vitamin deficiency?

My cat has been losing his hair for the last few months. He has no fur on his stomach and on top of his back, his fur is thinned out and he has a few bald patches. We took him to the vet countless times and pretty much ruled out allergies, cat litter, stress. I was doing some research about vitamin deficiency and found out biotin (or vitamin H?) can cause hair loss. So i was wondering if anyone knew any brands of cat food (dry or wet, whichever) that would help with this problem if it is from lack of biotin? Also, any other suggestions as to why my cat is balding? He'll be 4 years old in December. Thanks!I think my cat has a vitamin deficiency?
Go to the vet asap.I think my cat has a vitamin deficiency?
could it be ringworm????? I know that it can spread quite quickly. and that it is a little flaky
Is his fur falling out or is he licking himself bald? It might be anxiety. or stress. What's changed in his world? Check with the Spirit Essence people. I've gotten some great help from them in the past. See the link below.