Why do you own to stop taking Glucophage 24-48 hours prior to a heart cath?

Because they prefer that a diabetic's blood sugar be higher going into surgery so that you don't "bottom out". Also, you won't be allowed to chomp through for a long period prior to the procedure and may not be capable of eat afterwards. This is to protect you and preserve you from having a hypoglycemic response. I've been diabetic for 16 years.
The first answer is wrong (sorry Cyanne2ak). You own to stop glucophage (metformin) before a heart cath newly the same as you would a CT scan ("Cat scan"). It have nothing to do beside blood sugar levels. It have everything to do with how you body handle the drug when faced next to an iodine-containing contrast, like those used within a cardiac catherization or CT scan or IVP. Ideally, someone should avoid glucophage from the period 24 hours beforehand the procedure to 72 hours after the procedure. Taking the drug during this time could result in severe metabolic acidosis, sometimes to the point of release. It's not common, but it's well-described surrounded by the literature.