Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Get emergency help for a sudden severe headache with loss of vision, confusion, weakness, repeated vomiting, or collapse.
Emergency care is also appropriate for fainting, chest pain, severe dehydration, or immediate safety concerns related to an eating disorder.
Delayed puberty alone is not usually an emergency.
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Seek prompt medical advice for persistent headaches, vision changes, excessive thirst, frequent urination, or nipple discharge when not breastfeeding.
3
Does any of this apply?
Book an appointment
Arrange a routine medical appointment if:
Breast development has not started by age 13
Periods have not begun by age 15
Periods have not started within about three years of breast development
Puberty began but has stopped progressing
Growth has slowed or there has been significant weight loss
Concerns are affecting eating, mood, school, or daily life
Every sign above is quoted from the sofidex article on Delayed puberty in girls. If you are not sure, err upward — it is always reasonable to be checked.