My endo added the time release 500mg metformin to my regimen of diabetic meds in January. As he was gradually building me to 2000mg (if needed), he used the time release metformin. I was building it 500mg very 2 weeks and not taking the same total in am and pm when I was at the 500 and 1500 mg levels,so he said he wanted to use the time release tablets. Now that I am at 1000mg in am and 1000mg in pm, he will switch me to the 1000mg metformin tabs that are not time release to save me $10 on every 3 month fill. .That savings is because I dont use insurance and these are on those '$4 lists" and that is how the pricing works out. Not a big savings,$40 a year, but every dollar helps.