It dosnt really matter when you have the tests done. It dosnt need to be at certain time in your cycle as they work on averages with hormone levels, as in height weight and age. Your cholesterol does fluctuate but not periodically. and with a diabetes test they usually do a GTT Glucose tolerance test which takes 3 hours and 3 blood tests in a non pregnant woman (GTT tests both hormone and glucose levels) I was diagnosed with PCOS and had every test under the sun pretty much and i asked if they had to be done at a certain time and they said it makes no difference so dont be too worried just drink plenty of water before hand (if your allowed to) as it helps your blood flow better.
Take care sweety
Have a great day
Mel