When I went for my class 2, I had a fingerprick test for haemoglobin. Your diet "on the morning" shouldn't make any difference to this result.
I believe that some pilots have their lipid profile tested, (I'm not sure of the scientific reason behind this), the results would be altered if you fasted, but I guess the CAA should take this into account when interpreting the results.
I guess the medical is all about not dying suddenly whilst flying a plane, not much in the medical would predict this.