This does seem to be a controversial issue. My endo doesn't think it makes much difference. I would tend to agree based on my son's levels. One time I had my son's blood drawn around noon and it was a very difficult blood draw--they had to stick him about 3 times. Then when I got home I discovered that I had forgotten to give him his morning meds (the first and only time I have done that). I was upset and figured that I would have to get the levels drawn again. This was upsetting because the labs cost about $260 and because of the trauma it puts my son through every time. So I called and asked the endo if I should redo it and he said not to worry about it. Sure enough, all of his levels were very low in spite of everything. Since my son gets his morning dose between 6:00 and 7:00 in the morning it would be a pain to get him to the hospital before the dose. (But I would do it if I was convinced that it was important). I would be very curious to know how much levels can vary in the course of a day. And do you want to know what the highest level of the day is or the lowest? If anyone knows about any good articles on this topic I'd love to read them. From what I have read, levels should be checked every 3 to 6 months (unless they are off and then should be done more frequently) until the child stops growing. (New England Journal of Medicine, Dec. 27, 1990--Thanks Chris D.!) Then I don't think it's as critical. Good luck!