Hello, Metformins effects last for approx 10hrs @jim_bo230 so if you take them at night you're actually not getting much help during the day usually you are asked to take half the dose with breakfast and half with evening meal. If you can't cope with the nausea you could ask your doc to prescribe Metformin SR - slow release Metformin which can be gentler on the system, that might help. Taking the 1000mg at night is not doing you much good at all