A normal potassium level in the blood for adults is 3.5 to 5.2 milliequivalents per liter of blood. Children should have a level of 3.4 to 4.7 milliequivalents per liter, and infants should have a level 4.1 to 5.3 milliequivalents per liter, according to WebMD.
Some causes of too much potassium in the blood are kidney damage, severe burns, crushing injuries, heart attack or taking potassium supplements. Low levels of potassium are caused by vomiting, dehydration, malnutrition, kidney disease and diuretic medications, according to WebMD. Potassium that is too high or too low causes serious medical consequences such as abnormal heartbeat, paralysis, low blood pressure, nausea and weakness.