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 urgent or emergency help if you have:
A positive pregnancy test with one-sided pelvic pain, shoulder pain, bleeding, dizziness, or fainting
Very heavy vaginal bleeding, especially with weakness or faintness
Sudden severe abdominal or pelvic pain
Thoughts of harming yourself or feeling unable to stay safe
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 review sooner if the change followed cancer treatment or pelvic surgery.
Contact a healthcare professional promptly if you have unexpected or persistent bleeding, new pelvic pain, troubling treatment side effects, or symptoms of a thyroid or adrenal condition.
Severe weakness, repeated vomiting, marked dizziness, or faintness need urgent assessment.
3
Does any of this apply?
Book an appointment
Arrange a routine appointment if you are under 40 and your periods have become irregular or stopped for several months, especially if you also have hot flushes, vaginal dryness, or difficulty becoming pregnant.
The article also says
POI itself is not usually an emergency.
Pain or bleeding during pregnancy can have several causes, including an ectopic pregnancy, in which a pregnancy develops outside the uterus.
Every sign above is quoted from the sofidex article on Premature ovarian failure. If you are not sure, err upward — it is always reasonable to be checked.