Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Emergency symptoms, including confusion, difficulty waking, severe dehydration, bloody or green vomit, or sudden rapidly worsening pain, require immediate care rather than routine follow-up.
And for anyone, someone who:
Contact a clinician promptly for persistent vomiting, reduced urination, unexplained weight loss, pain that regularly wakes the person, ongoing pain between attacks, fever, blood in stool, or a major change from the usual pattern.
And for anyone, someone who:
Arrange a routine appointment if abdominal pain repeatedly interrupts sleep, meals, school, work, or activities.
Follow-up is also appropriate when attacks are becoming more frequent, home measures are no longer effective, or a prescribed treatment causes side effects.
A diary can make follow-up more useful.
Record when the attack started, how long it lasted, the location and severity of pain, associated symptoms, possible triggers, medicines taken, and the response to treatment.
For children, recording school absences and growth concerns may also help.
The article also says
The clinician may review whether the diagnosis still fits, whether tests are needed, and whether preventive treatment is helping.
The treatment plan may need adjustment as a child grows or as symptoms change.
Every sign above is quoted from the sofidex article on Abdominal migraine. If you are not sure, err upward — it is always reasonable to be checked.