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
Seek emergency help for vomiting blood or material resembling coffee grounds.
Black, sticky, tar-like stools may also signal bleeding, especially when accompanied by dizziness, fainting, confusion, a fast heartbeat, or shortness of breath.
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 care for:
Repeated vomiting or difficulty keeping fluids down
Unexplained weight loss
Trouble or pain when swallowing
Increasing weakness, breathlessness, or unusual tiredness
New symptoms while regularly using aspirin or another NSAID
Known gastritis with worsening or changing symptoms
3
Does any of this apply?
Book an appointment
Arrange a routine appointment if you have recurring or persistent upper abdominal discomfort, nausea, early fullness, or poor appetite.
You should also be assessed if symptoms regularly return after treatment or you frequently need non-prescription acid medicines.
The article also says
Iron and bismuth medicines can darken stools, but do not assume they explain black, tarry stools when bleeding is possible.
Every sign above is quoted from the sofidex article on Gastritis. If you are not sure, err upward — it is always reasonable to be checked.