I have never missed a period before and my cycles are always between 27-34 days. I was perscribed metformin for PCOS and take 1 -500mg tablet daily. I have only been taking metformin for 9 days. I do ovulate, but show signs of PCOS including acne, hair growth, excess weight around my middle, and some pain. I started taking the metformin on day 29 of my cycle. I am now at day 38 and still no period. Can metaformin prevent or delay your period? I haven't taken a hpt yet because I don't want to be disappointed.