Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency help immediately if the child:
Suspected medication poisoning requires immediate advice from emergency services or a local poison centre.
Contact the prescribing professional sooner if side effects are troubling, symptoms suddenly worsen, or a medicine does not seem to be helping.
Seek urgent medical help if a child develops severe agitation, hallucinations, fainting, chest pain, or a very fast or irregular heartbeat, particularly while taking medication.
Do not wait for symptoms to appear.
Arrange a routine appointment if attention, activity, or impulsive behaviour is persistent and is affecting school, friendships, family life, sleep, or safety.
It is also reasonable to seek help if a teacher raises repeated concerns or a child is becoming distressed about their performance.
Children already receiving treatment need routine follow-up to review symptoms, school and home functioning, growth, sleep, appetite, blood pressure, and possible side effects.
Every sign above is quoted from the sofidex article on Pediatric ADHD. If you are not sure, err upward — it is always reasonable to be checked.