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 for:
Severe, constant, or rapidly worsening abdominal pain
A swollen or rigid abdomen
A large amount of blood or black, tar-like stool
Fainting, confusion, marked drowsiness, or difficulty waking
Vomit containing blood or material that looks like coffee grounds
Breathing difficulty or other signs of a severe allergic reaction
Persistent symptoms, even without emergency signs, should still be reviewed to identify the cause.
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
Arrange prompt medical advice if diarrhoea lasts more than a few days, keeps returning, or occurs with fever, weight loss, blood, or significant abdominal pain.
Seek earlier assessment for babies, frail older adults, pregnant people, and anyone with a weakened immune system or serious long-term condition.
Seek urgent medical care if you cannot keep fluids down, pass very little urine, become increasingly dizzy, or have worsening signs of dehydration.
The article also says
Mild symptoms that are steadily improving can often be monitored with fluids and rest.
Every sign above is quoted from the sofidex article on Enteritis. If you are not sure, err upward — it is always reasonable to be checked.