My Husband Is Going Through Cancer Treatment At This Time.

My husband is going through cancer treatment at this time. He is taking chemo and radiation. His blood work is checked several times a week. He has a port in the chest , His blood work has had a very high level of potassium level. What foods should he avoid to keep this level down. He only has one kidney which only is 3. He started with bladder cancer, has lost the right kidney and now has cancer in the urther tube. I need to see about having a diet low in potassium. I am aware of some foods, but am not sure I am correct.