What Are The Side Effects Of Taking Metformin?

for the past 4 years I have been on 2000 milligrams of metformin to the morning and 2 at night. since then I've had a baby. for the past 6 months my cycles have been at 28 days. I figured because of this I could cut back on the metformin so now I'm only taking 1000. 1 in the morning and 1 at night of 500 ea. will it change like this commonly delay a period, because now I'm a week late. also what is a dosage that is typical of this type of behavior?