Use to get severe tommy ache when I started taking Metformin (modified release) tablets especially when it was increased to 4 tables a day (i.e. 2 at am and 2 at pm). I seldom have tommy ache and diarrhoea now. My blood sugar is well controlled with just 4 tables a day. I eat a lot of fruits/veg and carbohydrates such as rice, potatoes, yam. My blood sugar (fasting ranges between 5.1 - 6.7 most mornings. I only have problems (tommy aches, weakness/tiredness) if I eat late or miss my lunch or dinner.