to be concerned re weight?

[Flojo1979]

Ds is 7 and sooo skinny.
U can count his ribs easily and if I make a loop between my finger and thumb I can fit his upper arm in it.
I weighted him today and he's 25kg which puts him in the 50th centile but he's 133cm tall which is on the 98th centile.
He isn't very activate, preferring to stick his head in a book than run round.
AIBU or wasting time to get the gp to give him the once over? What could they do anyway?

Ok found nhs bmi calculator (goes off age, weight and height) he's just on the boarder of healthy and underweight so at least not underweight completely so I think I've no reason to worry, maybe relax a lil on the junk food.