Can Metformin turn poo dark and firmer?

[GillianS]

I was diagnosed T2 in 2010 and was on Metformin for a while but came off it as it caused stomach cramps that didn't go away. Since then and until about five weeks ago I have been managing on diet and exercise alone. Recently, though, my HBA1C went up to 56, having been in the upper 40s for years, so my doctor put me on 2x500g slow-release Metformin a day (1 at breakfast and 1 at dinner), with the first two weeks at just 1 a day. My BMI is a steady 18.5 and has been since diagnosis. Almost immediately, my poo changed from slightly loose and fairly light - which it has been for years - to firmer and much darker, but not black. I should point out that earlier this summer I had the full range of tests for bowel cancer which fortunately came up clear and then the regular annual bowel screening test about six weeks ago that was also clear. I have no other symptoms. I read that Metformin can cause diarrhoea but not have the opposite effect. I've 'Googled' the issue and searched here, but can't find anything else with similar issues. Should I be concerned or do I need to leave it a few more weeks for my body to adjust? TIA

 

[everydayupsanddowns]

That does seem unusual @GillianS - as you say often the gastric changes, if any happen, are in the opposite direction!

Glad you had the all clear at your bowel cancer screening.

Do you think it might be helpful to chat to a qualified pharmacist at your high street Chemist’s? They might have some expertise about drugs, rarer side effects, and possible interactions with other things you may be taking?

 

[Sarahp]

Are you on any other meds or vitamins? Iron tablets can do this. My experience of metformin is absolutely the opposite. Glad you have had a clear bowel screening though as that’s the normal worry with these changes.

 

[GillianS]

I was diagnosed T2 in 2010 and was on Metformin for a while but came off it as it caused stomach cramps that didn't go away. Since then and until about five weeks ago I have been managing on diet and exercise alone. Recently, though, my HBA1C went up to 56, having been in the upper 40s for years, so my doctor put me on 2x500g slow-release Metformin a day (1 at breakfast and 1 at dinner), with the first two weeks at just 1 a day. My BMI is a steady 18.5 and has been since diagnosis. Almost immediately, my poo changed from slightly loose and fairly light - which it has been for years - to firmer and much darker, but not black. I should point out that earlier this summer I had the full range of tests for bowel cancer which fortunately came up clear and then the regular annual bowel screening test about six weeks ago that was also clear. I have no other symptoms. I read that Metformin can cause diarrhoea but not have the opposite effect. I've 'Googled' the issue and searched here, but can't find anything else with similar issues. Should I be concerned or do I need to leave it a few more weeks for my body to adjust? TIA

Thank you, @everydayupsanddowns. I have just spoken to a pharmacist at Boots who has said to keep a while on it for a little longer and then perhaps go back to my doctor for another stool test, in case it's something from higher up my gut, i.e. my stomach.

 

[GillianS]

Are you on any other meds or vitamins? Iron tablets can do this. My experience of metformin is absolutely the opposite. Glad you have had a clear bowel screening though as that’s the normal worry with these changes.

Thanks, @Sarahp. I am also taking Pravastatin Sodium (which I've been on for at least 10 years) but by all accounts the combination of the two is supposed to be additionally beneficial. I don't take anything else except vitamin D in the winter but I've been doing that for years, too, with no obvious side-effects.

 

[Sarahp]

Thanks, @Sarahp. I am also taking Pravastatin Sodium (which I've been on for at least 10 years) but by all accounts the combination of the two is supposed to be additionally beneficial. I don't take anything else except vitamin D in the winter but I've been doing that for years, too, with no obvious side-effects.

I am glad the combination is beneficial for you, I hope this turns out to be nothing serious for you.