High potassium levels are diagnosed with a blood test, explains MedlinePlus. The test measures the amount of potassium in the fluid portion of the blood, which is called serum. A normal potassium level ranges from 3.7 to 5.2 milliequivalents per liter, states MedlinePlus.
The potassium blood test is performed on a blood sample drawn from a vein, notes MedlinePlus. Doctors order this test for people who have signs of hyperkalemia, which is the medical term for an elevated potassium level. Weakness, slow heart rate and abnormal heart rhythm are some of the signs of hyperkalemia, states WebMD. Doctors also order this test to monitor people who have signs of heart problems or high blood pressure, explains MedlinePlus.
Kidney disease is the most common cause of an elevated potassium level, but there are other causes. Kidney failure, Addison's disease, metabolic acidosis and respiratory acidosis can cause elevated potassium levels. Because aldosterone helps regulate the amount of potassium in the blood, having less aldosterone than normal can cause hyperkalemia. Other causes of an elevated potassium level include certain medications, blood transfusions and crushed tissue injuries.
Treatments for hyperkalemia include intravenous insulin and glucose, sodium polystyrene sulfonate, diuretics and dialysis, states WebMD. Dialysis is usually reserved for people with potassium levels so high that they are life-threatening.