Hi My Father Is A Diabetic Patient Since 11 Years.

Hi My father is a diabetic patient since 11 years. He's consulting with the same doctor since 10 years. He suddenly became anaemia and hemoglobin count has become half. He's having fatigue, dizziness. Recently he even got some skin rash. We consulted a dermatologist for that and took medicines for more than a week. Still there is no improvement. The dermatologist suggested it could be due to diabetic medicines itself. When consulted with diabetic doctor, he said it's nothing because of diabetic medicines. What could be cause? what is the action which I can take now. He's growing weak day by day.