Co Q10 improves BP, glycaemic control: trial with type 2 diabetes
This study used a very reasonable dose of 200 mg/day of CoQ10 and showed favorable effects in diabetics. While this effect was small, keep in mind that CoQ10 supplementation will have a wide range of other beneficial effects (as opposed to pharmaceutical interventions, which typically have a wide range of deleterious effects) and that CoQ10 would only be one tool in the natural approach to diabetes and HTN.
Coenzyme Q10 improves blood pressure and glycaemic control: a controlled trial in subjects with type 2 diabetes.