Doctor's Note: What's Normal and What's Not for Your Cycle

As a gynecologist, I am often consulted for menstrual cycle concerns. Daily, in fact. If you are dealing with problematic periods, you're in good company. About one-third of all visits to the gynecologist are regarding abnormal uterine bleeding.

Many times, women may not realize that their periods are abnormally heavy, or that the periods they thought were irregular are actually perfectly normal. I'm here to set the record straight on your Aunt Flo.

A healthy menstrual cycle

A menstrual cycle is typically 28 days in length, but a normal, healthy menstrual cycle can vary between 21 and 35 days.

After all, our bodies don't read textbooks, and certain events, such as illness or stress, can cause slight variations in normal. The flow should last between three and seven days and is usually heaviest on the second and third day of bleeding.

How it all works

Day 1 is the first day of bleeding, when you begin to shed the lining of your uterus as your monthly period. After you finish bleeding, a hormone called estrogen begins to rise, causing the lining of the uterus to build up again in preparation for a possible pregnancy.

Meanwhile, your ovaries are busy preparing an immature egg for ovulation. The immature egg lives inside an ovarian follicle, or fluid-filled sac, which is often seen on ultrasound and is a completely normal finding.

During the first half of the menstrual cycle, the immature egg gradually increases in size until ready for ovulation, which occurs mid-cycle. During ovulation, the mature egg is released from the ovary and captured by the fallopian tube, where it can be fertilized by sperm if the timing is right.

If the egg is not fertilized, then progesterone levels in your body drop, signaling your body to shed the lining of your uterus as your period, beginning the cycle all over again.

An abnormal period

Cycles that are considered abnormal fall outside the 21-to-35-day range or are heavier than "normal." However, average menstrual blood loss is difficult to define. The amount of blood loss is typically 2 to 3 tablespoons, according to the Centers for Disease Control and Prevention (CDC), but that can vary by individual.

If you are concerned about your flow, talk to your doctor, because they can best determine the health of your period.

In a nutshell, as long as your period is occurring approximately once a month, your flow lasts three to seven days, and you do not need to change your period protection more than every two hours, this is considered within normal limits.