Hiya! I am in the UK & our levels are in the hundreds! I don't know what the units are called but they read umol/L for example, my last blood test level was 250umol/L
In America, their levels ARE different, I was told that the calculation is ROUGHLY our levels divided by 66, so my last level would be 3.7 in American terms!
I wouldn't be able to tell you if the type of PKU could change as your little one gets older, as I'm no dietician, but I imagine you wouldn't know until you started introducing more foods and seeing how they effect the levels! If WA is a bit new to it, I could ask my dietician if she knows?!
As clenk said, levels can change by the day! If things need to be changed, they can be implimented pretty quickly! I am currently 39 weeks pregnant and do a blood spot test 3 times a week! The levels (generally don't but) can change by 100umol/L in a week, that is when my dietician puts me up or down (more often up than down) in exchanges!
I hope this has helped a little bit?! Do feel free 2 message me if you have any more Qs! I will try my best to answer, if not I will try to find out! x x x