Colonoscopy

I had a colonoscopy that will have to be repeated because the bowel prep didn't work properly. That's the first time this has happened to me. My previous colonoscopies were before I started taking dapagliflozin, metformin MR and sitagliptin.

Anybody have any tips on good bowel prep for colonoscopy with diabetes? I've been given senna tablets and advised to take seven days worth rather than five and to have a low fibre / residue diet for seven rather than three days.

HCPs are so specialist nowadays in what they do, that I'm not confident the endoscopy unit's medics and nurses understand diabetes properly. [They say diabetes makes food move through the bowel slower - I don't know if that's really the diabetes itself or the medication I take to manage it*] I'm also not confident the pharmacist at my GP (who is the person I see for diabetes) understands bowel prep for colonoscopy. I'm hoping some other diabetics have had similar problems and can explain how they've achieved an empty bowel.

* I say this, because when I last had colonoscopies in 2023, the bowel prep worked fine. The last sigmoidoscopy was 13 months before I was diagnosed with diabetes. I will never know, but I had an HbA1c of 106 at diagnosis and I suspect had had diabetes for years before I was diagnosed. So I am suspicious that the thing hindering the bowel prep from working is some or all of metformin / sitagliptin / dapagliflozin, with my mind hedging towards the metformin as the most likely culprit.