5 Replies. The most commonly deficient vitamins for people dealing with rheumatoid arthritis are vitamin C, vitamin B6, folate (vitamin B9), vitamin D, vitamin B12 and vitamin E. It is preferable to get these vitamins in your diet however if that is not possible then supplements can be used. Replies. The most commonly deficient vitamins for people dealing with rheumatoid arthritis are vitamin C, vitamin B6, folate (vitamin B9), vitamin D, vitamin B12 and vitamin E. It is preferable to get these vitamins in your diet however if that is not possible then supplements can be used.