I've got loads of worries about starting Metformin, obviously, cuz I'm starting threads left and right and checking this forum obsessively. My latest concern is that the side effects of Metformin are supposedly worsened by "excessive exercise." Ok, well, I train for marathons, and I run anywhere from 15 to 30 miles a week. I would guess that counts as excessive exercise. In the marathon world we use electrolyte-replacements like GU and Gatorade etc. so that our bodies have some fuel to run on when we're going 90+ minutes. I'm wondering how that is going to jive with Metformin...it also sounds like it could really provoke the Lactic Acidosis if I'm not extremely careful. I've got a call in to my pharmacist so hopefully I'll get a good answer, but I'm curious if anyone here has any experience with endurance training while on Metformin. Thanks!

Hey Snoozlebug, (love the name!) I have heard that excessive exercise can bring on low blood sugar, but I haven't heard it having an effect on lactic acidosis. Is it possible you have that and lactate production crossed somewhere?

What I understand is that the reason "excessive exercise" is a problem is the risk of dehydration, which is a cause of lactic acidosis apparently. I gather that the -osis is an extreme continuation of lactic acid buildup in the muscles, which is common in any endurance sport, and somehow Metformin provokes this extreme condition. I could be wrong though, if I am, someone tell me! I wish I were an exercise physiologist! All this metabolic science makes my brain hurt

Ok from the limited knowledge I have, I know that when you exercise, your insuline resistance improves and sometimes to the point you might no need Metformin anymore. My Endocrinologist said that as I exercise, he would like my insuline resistance checked every six months to see if it improves.

That said, I have read from the Glucophage instruction leaflet that Lactic Acidosis is more likely to develop if you drink too much alcohol while taking Metmorfin. It does not mention anything in relation to exercise, so I cannot be sure.

Alright so I e-mailed my doctor and her answer to this is that yes, dehydration (caused in any way, and by both exercise and consuming alcohol) provokes Lactic Acidosis, but that the people mainly at risk for that while on Metformin are older people with marginal kidney function to begin with. Phew! I'm good to go!