I have been working out again since mid January 2013. I am an almost 43 year old, female, 5 foot 5 inches, 134lbs (have gained approximately 6lbs of muscle). I am currently lifting weights along with some cardio at least 3 to 4 days per week. Last year I started lifting and stopped at about the 7 month range due to family obligations/time constraints. Since starting back this January, I have noticed my menstrual cycle is a little shorter. This is a great thing! My menstrual cycle has been crazy since having my last child who is 12. My average monthly cycle would be....on for 3 to 4 days, off 2 days, on another 3 to 5 days and I was starting every 21 days. It has been horrible. I have been to my Ob/Gyn, ultrasound shows nothing. She put me on 2 different medications but it didn t seem to help. I am not a medicine taker. I am and have never been on medication of any sort other than birth control 20 years ago that I couldn t take. My husband had a vasectomy 12 years ago. My question is, since I have started back lifting weights, I have started eating a decent amount of protein and taking Creatine . I am very happy with the results of exercising and watching what I am eating but I am wondering does Creatine in any way cause ones menstrual cycle to be abnormal. I should have started 2 weeks ago but haven t. And there is NO way I am pregnant. But I do have my usual cramps, my legs ache and I feel at any time I am going to begin my monthly cycle. Could this be pre- menopause at my age, exercise, supplements (creatine) or a combination of both? Thanks in advance for your help!