Blood pressure in a 15-year-old child is considered normal when the systolic pressure is between 90 and 139 mmHg and the diastolic pressure is between 60 and 89 mmHg. Under normal circumstances, the systolic blood pressure of a 15-year-old child is between 90 and 139 mmHg, and the diastolic blood pressure is between 60 and 89 mmHg. Blood pressure refers to the arterial pressure of the physical circulation, which generally rises slowly and gradually with age, and is higher in middle-aged and older people than in young people. Primary hypertension is less likely to occur in 15-year-olds, but secondary hypertension may be present if the child has high blood pressure. Secondary hypertension may be associated with kidney disease, aortic constriction, or other causes, and should be treated promptly to remove the cause. If a 15-year-old’s blood pressure is above normal, it is recommended that he or she be seen by a doctor to determine the cause of his or her condition and receive targeted treatment.