The levels of tetrodotoxin (TTX) in the serum and urine were investigated by using LC-MS method in healthy male wistar rats after oral administration with single dose of 60 nmoleTTX mixture. After treatment, male wistar rats were randomly divided into three groups: (1) rats drink distilled water; (2) rats drink saline solution; (3) rats drink alkaline electrolyzed (AE) water. The serum and urine samples were collected at intervals between 2 hr to 60 hr after orally administration. It was found that TTX can be detected from serum and urine up to 60 hr the max that was tested when intoxicated poisoning occurred. The highest amount of TTX appeared after 4 hr and 6 hr in the serum and urine, respectively. When the rats took AE water, TTX was secreted earlier from the serum and urine. It indicates that AE water enhances the excretion of TTX in the rats. Moreover, LC-MS is useful for detecting TTX in serum and urine samples and may have diagnostic potential for TTX intoxication.