Metformin side effects?

I take one metformin at breakfast and feel fine. At lunchtime I don't take one and feel awful around an hour after eating, I feel dizzy and sick. Is this a side effect from the metformin, or is this being caused by a spike after eating? I am keeping to a low carb diet but feel dreadful after lunch, I feel queasy after evening meal but not as bad as at lunchtime. When I wake in the morning I feel ok, it's just after lunch.....