How much weight can a 44lb 7yr old lose during illness before indicating need to go in? just keep hydrating & no worry?? (1lb+down in 10days) flu-like

Probably good idea..: to get seen. Hydration is very important, and the expectation is that the appetite should rebound soon. If he's still experiencing fever or severe symptoms I'd still recommend getting him seen. If the symptoms are resolving you can monitor a bit longer. If the weight loss exceeds 5% (2.3 lbs) then that would be another reason to get seen.