In children, if they are between 1 and 12 years of age, alkaline phosphatase 300 U/L is normal and does not matter. However, if a woman is >15 years of age or a man is >25 years of age, an alkaline phosphatase of 300 U/L is usually abnormal and needs to be combined with the cause to determine if it is important. If a child is between 1 and 12 years old, the normal reference value for alkaline phosphatase is <500 U/L, so if the value is 300 U/L, it is mostly normal and usually does not matter. However, if the alkaline phosphatase is 300 U/L in a woman >15 years of age or a man >25 years of age, it is usually abnormal and needs to be combined with the cause to determine if it is important. If a child’s alkaline phosphatase is caused by a high-sugar, high-fat diet, it does not matter; if it is caused by erythromycin, gentamicin, barbiturates and other drugs, it is transient and can be restored by stopping the drug, and it does not matter; however, if it is caused by obstructive jaundice, cirrhosis of the liver, lung cancer, osteoblastoma, hyperthyroidism, and other diseases, then it is important, and active treatment is needed. When alkaline phosphatase is abnormally elevated in children, the cause needs to be clarified under the guidance of a doctor so that active treatment can be carried out.