Some people have quite severe side effects, others experience fairly mild side effects that disappear after a while, many tolerate Metformin really well and do not suffer any side effects at all.
Metformin is a mild drug that helps a little but if you are waiting to see a noticeable improvement, you may be disappointed.
Metformin works by restricting the amount of stored glucose released into your blood from your liver, it also helps to improve your insuln resistance a little.
What it will not do is make much of a difference to the sugar that gets into your blood from your diet.
The glucose you get from eating carbs will cause your blood sugar to rise, Metformin can not help with that.
To actively reduce blood sugar levels, more effective drugs are needed, like insulin or drugs that force your pancreas to produce more insulin.
Most of us find that reducing the amount of carbs in our diet is a far more effective way to reduce our levels.