Not weed in 12 hours, not eating much…dehydration?

Hey My little boy hasn’t had a wet nappy since his morning one (he woke at 5, so who knows when the last one was) He hasn’t eaten much in the past couple of days, but no fever. He’s about to get home from nursery and I know lethargy is a big tell tale of dehydration, but the poor lads been at nursery for 6 hours after a poor nights sleep and a 5am wake up and no nap! so he’s gonna be knackered anyway. So going to be hard to use that as a symptom. What would you do? hospital visit? I would’ve put him down to bed at 5:30 tonight given his early rise, but obviously won’t if he hasn’t weed yet. TYIA❤️