Does metformin 500 cause missed periods?was put on it for pcos but had regular cycles before tht.was also diagnosed with hypothyroid but under control

No: Assuming you have pcos you shouldn't have amenorrhea. Take a pregnancy test.

Generally no: Metformin is used to induce normal menses if you have pcos. Usually you need at least 1000-2000 mg/day in divided doses. Hypothyroidism can also affect periods, as can many other disorders, including pregnancy, if the metformin was able to restore your fertility, which is common.

No!: I have never seen metformin interrupt menses. However, the underlying metabolic syndrome, causing pcos may have gotten worse. Also, a low thyroid which you had causes excessive periods and bleeding. Correcting this may have given the impression that your menses were normal. Finally, if you are over treated with thyroid-you will be amennorheac.