A normal menstrual cycle is the time from the first day of your menstrual period until the first day of your next menstrual period. The average length of a menstrual cycle is 28 days, but it can range from 21 to 35 days and still be considered normal. The duration of a period can last anywhere from 2 to 7 days, and the average person loses anywhere between 1-6 tablespoons of menstrual fluid during each period. It is normal for periods to be light or heavy, and for some people to have a menstrual period for only three days. The menstrual cycle can change from a persons teen years to their 40s or 50s, and it is normal to have longer cycles or a heavier period flow when first starting menstruation. It can take up to three years for young people to have regular cycles after they begin menstruating. If a persons menstrual cycle is longer or shorter than the average range, it can still be considered normal as long as it is regular. It is important to note that "normal" menstrual cycles can vary from person to person, and can change over a persons lifetime.