Metformin and Fasting (For 24 Hours)


Happy weekend!

I have a question for the group: does anyone dose metformin during alternate day fasts or 24-hour fasts?

I am curious about fasting on Sundays (last mea Saturday night, first meal Monday at noon) and am wondering if I should dose my metformin on Sunday when fasting? I guess I’m curious is abstaining from Metformin for a period of 36 hours would reduce the half-life of Metforming so much that it’d lose effect?

I may be overthinking things, splitting hairs, but hey, this is super interesting stuff so I welcome all feedback!

(Michael) #2

I will preface by saying not 100% sure, but pretty confident in saying that you can skip a Metformin without any issue, and therefore skipping when not eating would be fine. In fact, I would recommend it since your body is not processing carbs while you are fasting, taking it to help digest non existent carbs would not really help. If someone knows better, feel free to interject.

(KM) #3

I don’t know that I know better, but I do know that Metformin is not a … hmm. Directly interacting drug? It takes several weeks for it to start working, it’s not something that has an immediate impact on what you’re eating in any particular moment. (A few months ago my husband had some left over, and I’d questioned whether I could take it occasionally as a “counter-carb” to prevent a glucose spike if I wanted to have some carbs or I accidentally slipped up. The answer was No.) assuming that information was correct, I don’t think dosing for your weekend fast is necessary or maybe even advisable.

(Doug) #4

I don’t bother taking it when fasting.

Also wonder if it matters, either way…? I’ve never felt any effects, good/bad or side effects, even when taking it.


This 2013 UK article makes some interesting points although I wonder about their take on skipping meals and fasting. As I read this article, the implication is that metformin does have an immediate effect even if some of the effects are cumulative but I am not an expert. It seems it is best to discuss with your prescriber what to do when fasting,be%20taking%20it%20with%20meals.

(Kinnessa ) #6

Metformin typically has a half-life of around 6 hours, meaning it stays active in your system for a relatively short time.