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
Call emergency services if you faint and do not recover promptly, become confused, have severe breathing difficulty, or are too weak to stand safely.
Vomiting with one-sided abdominal pain, shoulder-tip pain, vaginal bleeding, or collapse in early pregnancy needs emergency assessment because these can be symptoms of an ectopic pregnancy.
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 urgent medical assessment if you:
Cannot keep fluids down
Pass very little urine or have dark urine
Feel dizzy when standing or have nearly fainted
Have repeated vomiting with clear signs of dehydration
Vomit blood or material that looks like coffee grounds
Have severe abdominal pain, fever, confusion, or a severe headache
Have painful urination or blood in your urine
Cannot keep essential medicines down
An ectopic pregnancy develops outside the uterus and requires urgent care.
And for anyone, someone who:
is vomiting and cannot keep fluids down
3
Does any of this apply?
Book an appointment
Routine assessment is also appropriate if symptoms are not improving, you are losing weight, or your current treatment is not helping.
The article also says
Contact your midwife, doctor, or pregnancy care service soon if nausea or vomiting is interfering with eating, drinking, sleep, medication, or normal activities.
Every sign above is quoted from the sofidex article on Morning sickness. If you are not sure, err upward — it is always reasonable to be checked.