Will my doctor cancel the colonoscopy at the last minute if my bp or blood sugar drops too low upon checking in at surgery center?

Possibly: Colonoscopy is an elective procedure. If you're unwell for any reason, it will be postponed. However, what you consider to be too low may not be the same as what the doctor considers to be too low.

Colonoscopy: Colonoscopy is performed under intravenous sedation. Low blood pressure and low blood sugar make you high risk to complications.

Not likely: Your blood sugar should not be an issue unless you are a diabetic on medication. If so, hopefully your doctor has outlined a strategy to prevent low bs (often withholding am Insulin - taking a lower dose, drinking orange juice, etc.) to prevent a problem. Low blood pressure is not often a problem unless you are on BP meds. Most low BP responds to fluid before the procedure.