12 year old child has heart rate of 130, no symptoms.?

Circumstances?: Could be normal depending on circumstances of exercise, diet, illnesses, medication use. Most common reason for an otherwise healthy 12 yo to have tachycardia is consumption of energy drinks or chocolate. Also you should consider drug use, such as weed and tobacco. Consult your pediatrician for a proper evaluation.

See a doctor: The child could have a number of diagnoses. For example he could have diagnosis of anemia, or he could have a heart arrhythmia. He needs a physical examination to begin the evaluation.