Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Get emergency help for confusion, fainting, difficulty waking, severe weakness, or very little to no urine.
These can be signs of severe dehydration.
Vomiting blood, material that looks like coffee grounds, or bright green fluid also needs emergency assessment.
Sudden severe abdominal pain, a rigid or swollen abdomen, or trouble breathing may point to another serious problem rather than uncomplicated viral gastroenteritis.
Routine medical follow-up is different from emergency care.
Seek urgent medical advice if you or someone you care for cannot keep fluids down, is urinating much less than usual, or has clear signs of dehydration.
Young babies, frail older adults, and people with weakened immune systems should be assessed sooner because they have less reserve.
Urgent assessment is also appropriate for:
It is reasonable to arrange a non-urgent appointment for bowel changes that linger after recovery, repeated episodes, or concerns about nutrition and weight.
Every sign above is quoted from the sofidex article on Viral gastroenteritis. If you are not sure, err upward — it is always reasonable to be checked.