See a doctor if you're worried.
Diagnosing hyperactivity isn't easy, but as soon as your child's excessive behaviour becomes a problem for them, the rest of the family or at school, it's recommended that you seek medical advice.
If it turns out that there isn't a problem, a consultation will nonetheless reassure everyone involved, or it might detect other reasons behind your child's behaviour and enable you to work to resolve their difficulties.
Contact your GP, who will refer you to a specialist if necessary. The specialist will normally be a a psychiatrist or pediatrician who will carry out a detailed assessment, which may include interviews with your child, yourself and teachers.