You are best off to discuss this with your Dr. Some supplements can interact negatively with prescribed medication.
Below is a link to an article I would like you to read - particularly the first few paragraphs. www.sparkpeople.com/resource/nutrition_art
Probably one of the best things that your Fiance can do is to consume a lot less sodium, if he consumes alcohol, to limit that, and if he smokes, to stop that.