How long to get over stomach bug?

[Impressedmuch]

Hi, my dog vomited this morning and is just lying there, not bothering much with anything.

He's got gastroenteritis. He drinking but not eating for 12 hours. How long does it take until they look more lively? I mean human's feel rubbish, but I just feel sorry for him, he looks so sad.

I'd give the vets a ring and see what they think?assuming they are the ones who diagnosed gastro.
What medications is he on?
It can take time for some of them to kick in but if hes still quite unwell he may need intravenous fluids and stronger meds.
Elderly animals often dont bounce back as quickly as the young and need more care.