One of the biggest risk factors for hyperkalemia is reduced kidney function. When kidney function declines, waste products known as creatinine and blood urea nitrogen build up in the blood. People with high levels of creatinine and BUN are at risk for developing high potassium levels. Another risk factor for hyperkalemia is long-term used of angiotensin-converting enzyme inhibitors. These medications are used to treat heart failure and hypertension by relaxing the blood vessels. People over the age of 70, and those who have congestive heart failure, are also at risk for hyperkalemia.