@RobertaSturges - Hello. Did you get the Glucosamine Gel on Prescription from your GP? If so, then use it. If not, then read the leaflet in the box. And if still unsure? Go to a chemist and ask a Pharmacist - but tell them you are Diabetic.
This drug interaction checker shows no adverse reactions between metformin and glucosamine, but it's definitely always sensible to obtain professional medical advice about any concerns you have.
Having said that, I've been taking non prescribed glucosamine/chondroitin tablets for years and it never actually occurred to me to check when I became diabetic , but I've never had any problems.
Robbity
PS I found that my (apparently NOT arthritic) knees were a lot better in general when I started eating an LCHF diet, but I do still need the glucosamine...
No it wasn't prescribed. I do normally ask a pharmacist but for some inexplicable reason on this occasion I didn't. I have lost just over 2 st. through slimming world but still got a long long way to go.