Trimethoprim is known to cause high blood potassium because it interferes with the kidney elimination of potassium. Penicillins such as amoxicillin do not usually cause potassium problems. Your husband’s physician should be able to determine if he is a diabetic or not. A fasting blood sugar, a blood sugar taken two hours after eating a meal and a hemoglobin A1c should be done if one is attempting to make a diagnosis of diabetes mellitus. I would suggest that you consult with your husband’s physician about your concerns.