The cause of Terri Schiavo's collapse was determined to be cardiac arrest. Her medical chart contained a note that "she apparently has been trying to keep her weight down with dieting by herself, drinking liquids most of the time during the day and drinking about 10–15 glasses of iced tea." Upon admission to the hospital, she was noted as suffering from hypokalemia (low potassium levels): her serum potassium level was an abnormally low 2.0 mEq/L (the normal range for adults is 3.5–5.0 mEq/L). Her sodium and calcium levels were normal. Electrolyte imbalance is often caused by drinking excessive fluids. A serious consequence of hypokalemia can be heart rhythm abnormalities, including sudden arrhythmia death syndrome. Schiavo was eventually switched from being fed by a nasogastric feeding tube to a percutaneous endoscopic gastrostomy (PEG) feeding tube.