The most common causes of high potassium levels are chronic kidney disease and acute kidney failure, according to Mayo Clinic. In these two cases, a person's kidneys cease to function properly and are unable to filter excess potassium from the blood, states WebMD.
Addinson's disease can also cause a person to experience high potassium levels, states WebMD. This is because the disease affects the production of a hormone called aldosterone, the hormone that tells the kidneys to filter out excess potassium. When not enough of the hormone is produced, the kidneys never receive the signal to begin filtering. Also, excess potassium in a person's diet can lead to excess potassium in the bloodstream.
Another disease that can cause high blood potassium is rhabdomyolysis, according to Mayo Clinic. This disease is usually seen in people who abuse alcohol or drugs, which causes the fibers in their muscles to break down and release potassium in the bloodstream. Uncontrolled diabetes, burns and tissue injuries are other conditions that can cause the body to release more potassium, states WebMD.
Finally, certain medicines can interfere with the kidney's ability to filter out excess potassium, according to WebMD. Medicines such as penicillin G, trimethoprim and azole antifungals can sometimes cause the condition. Also, herbal supplements, such as lily of the valley, milk thistle and Siberian ginseng may increase the amount of potassium in the body.