What's the best alternative medicine for diabetes?

Depends. The only way to treat type one, Insulin dependent diabetes, is with insulin. In this disease, your body makes no insulin. There is no alternative; you take your Insulin or you die. Type two diabetes involves Insulin resistance. 80% of people with this problem are obese. Ala (a type of fatty acid) has been shown to help in some studies. Recently cinnamon has drawn attention as a treatment.
Chinese medicine. Would be the best additional medical treatment. Do not stop any medicines you are on. Add the additional help and see how your body improves over time.