Bilberry and Type 2 Diabetes

I have a friend in Ukraine who has Type 2 diabetes and he asked me to find some tea or herbs which will assist in lowering his diabetes. He does not take any insulin. He has been watching his diet and that has helped him to lower it plus exercise. I looked up bilberry leaves and it mentions it helps in lowering diabetes but it can be toxic. When does it become toxic for the liver? I know that taking any medication for a prolonged period is not kind to the liver. Could you please be so kind and suggest how much of this bilberry he should use and when to stop to give the liver time to breathe. Also, what other herb does Richters have to help with diabetes?

Regarding the toxicity of bilberry leaf, please see: www.richters.com/questions-and-answers/02-19991220-1
Regarding the proper use of bilberry leaf: www.richters.com/questions-and-answers/02-20030920-1
However, bilberry fruit and blueberry fruit have marked blood sugar control and regulation properties without the concern for toxicity. They can be eaten freely. Native cultures here in Ontario use it as part of their daily diet. 1/2 to 1 cup of fruit three times per day has shown great benefit and promise.
Regarding other herbs for diabetes, this question has been addressed before. Please see: www.richters.com/qa-search.cgi?search=type%202
www.richters.com/qa-search.cgi?search=diabetes