I have been a Type 2 diabetic for some time now and up until recently I managed my blood glucose with diet and exercise. Recently my blood sugars have gotten out of control (mostly due to complacency on my part) and I have been put on Metformin.
Initially I was put on Metformin HCL ER, and after a few weeks of gradual dosing up from 500 mg to 1500 mg with split dosages I became very ill with extreme GI upset and fatigue. From both my research and my doctor's knowledge of Metformin this we contrary to expected behavior.
Normally the Extended Release (ER) form of Metformin is easier on the gastrointestinal system than the original formulation.
I had read on some online forums that others had similar experience with both forms of Metformin and they found that cracking or crushing the tablets helped with the symptoms. I decided to try cracking the tablets before swallowing and found some relief, but not enough to fully mitigate the symptoms.
My doctor switched my prescription to the original form of Metformin and it did help with both the GI upset and the fatigue, and I found that cracking the tablets even more helped to reduce my fatigue to where it was no longer a problem, and to where the GI upset was a minor inconvenience.
My thoughts are one of the buffering or binding agents of the capsule was causing the fatigue and extreme GI upset. I did some research and found this interesting article comparing the use of Metformin in capsule form as opposed to tablet:
Severity of Gastrointestinal Side Effects of Metformin Tablet Compared to Metformin Capsule in Type 2 Diabetes Mellitus Patients - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5463552/
The study shows there was an improvement in both reducing GI upset and glucose management - "Capsular form of metformin may result in decrement of GI side effects and intolerability in diabetic patients and may be an option for those that metformin is an appropriate medication for them but cannot tolerate it due to the mentioned side effects."
Unfortunately Metformin is not readily available, and most insurance companies will not pay for compound pharmacies providing Metformin in capsule form.
I will continue to research this subject and either add links to this article or post a new article. Feel free to comment on your experiences with Metformin.
Here is an interesting video I thought I would include from the Pharmacist Tips Youtube channel titled Metformin 500 mg and Side Effects