| Two months is far, far too early to say whether you are becoming resistant to the medication. It can take weeks for the body to stabilise after starting a new medication.
Taking glipizide is only one line of attack on your diabetes and the problem is that as soon as your body detects that your sugar levels are falling your liver will kick in and release glucose, particularly if you are exercising and that is why some people are also on Metformin, one of whose functions is to reduce glucose release by the liver.
Sugar level is a balance between the effect of your particular medication, your state of health (whether you have a cold or infection etc - which raise sugar levels) and your level of activity. a small change in your level of activity whether it's physical or mental or both, can have a seemingly large change in sugar levels (particularly if you are on solely glipizide)
If I were in the 50s, I would be much too low and I would take emergency action. If I stayed in the 90s I would be very content with my level of control.
My advice is, keep testing and find a regime which keeps you at the level that you have decided upon in conjunction with your medical team and which suits your lifestyle and keeps you comfortable.
__________________ Peter
63,Type 2, Diagnosed Dec 04 Medication - Metformin 850mg x 3; Pioglitazone (Actos) 30mg x 1; Gliclazide 160mg x 2; plus stuff for hypertension & cholesterol with Aspirin E/C for the cardio/vascular system  I have to keep smiling - there's no other choice - but I do growl occasionally  | 
