Yes I have had one, but I wasn't taking any diabetes drugs then, so I can't help you with advice there. I took my blood pressure tablet and warfarin as usual. The immediate effect on my blood sugars was fine, (they stayed around 5.5- 6.5) however I found the diet they asked you to eat the day before the fasting day was awful and made me crave carbs again, also the laxatives are flavoured with artificial sweetener which I have always found to be very addictive, so I craved diet drinks for weeks afterwards. I didn't find going without food a problem - after eating white bread and sweets the day before the 24 hour fast was a pleasure.
The main problem for me was that no one explained quite how powerful the laxatives were! When you start taking the picolax, you need to stay very close to a loo. If I ever need to go through a colonoscopy again I will take a chair and stay in the bathroom with a book, being in a room next to the bathroom was not close enough! The colonoscopy itself wasn't that bad for me, embarrassing but not painful, just uncomfortable. I wasn't sedated, I just had a couple of puffs of entonox. Good luck for yours