f you suspect that you are becoming dehydrated.
If you are vomiting a lot and unable to keep fluids down.
If you have blood in your diarrhoea or vomit.
If you have severe abdominal pain.
If you have severe symptoms, or if you feel that your condition is getting worse.
If you have a persisting high fever.
If you have a fit (seizure).
If your symptoms are not settling; for example, vomiting for more than 1-2 days, or diarrhoea that does not start to settle after 3-4 days.
Infections caught abroad.
If you are elderly or have an underlying health problem such as diabetes, epilepsy, inflammatory bowel disease, kidney disease.
If you have a weakened immune system because of, for example, chemotherapy treatment, long-term steroid treatment, HIV infection.
If you are pregnant.
If you suspect that you may have contracted food poisoning from eating restaurant or takeaway food (see below).