Period questions: What may cause an irregular cycle and when to see your doctor

Your period comes at the same time every month -- except when it doesn't and you're not pregnant. Millions of women wonder why it doesn't always run like clockwork, and when to see a doctor. Truth is, there's nothing fun about getting your period. Still, when it arrives on time a lot of women think of it as a sign that all is well on the inside. But what about when there's something not quite right about it?

"I tell patients, if (an irregularity) just happens once out of blue, first take a home pregnancy test. If it's negative, give it another month," says Cape Girardeau gynecologist Dr. Tami Williams. "If it becomes a persistent problem, see your doctor. Everyone has an off period once in a while."

Period irregularities range from when -- or in some cases if -- it arrives, how long it lasts and how heavy or light the flow is.

"Women tend to complain about bleeding too much or too little," says Kathy Blevins, women's health nurse practitioner and forensic health director of Beacon Health Center. "As ironic as it sounds, both are perceived as abnormal to most women. In reality, there are some variances in women's normal period cycles, and due to the vast use of oral contraceptives, we have forgotten what normal cycles were like."

As for Williams, she says a heavy flow is the biggest complaint she hears, but not the only one. "I get a lot of questions about small blood clots," she says. "Those are normal. Large ones are not."

The first step women need to take is educating themselves on what constitutes a normal period. The menstrual cycle, which is counted from the first day of one period to the first day of the next, isn't the same for every woman. Most women have a period every 21 to 35 days that lasts about two to seven days.

"As long as there are 21 days between periods, that's OK," Williams says. "Less is concerning."

As for the duration and flow of your period, Blevins offers these guideline: "As a general rule, periods which last longer than seven days and bleeding which saturates a pad an hour is too much bleeding and can lead to anemia."

So what happens when your period is, for example, heavier than normal one month?

First, don't jump to the worst-case scenario. "Irregular periods and the character of the bleeding is triggered by hormones which are greatly affected by stress and general health and well-being," Blevins says. "Illness, medications, stress can all play a role in character of periods."

Weight is also a factor, Williams says. "If you're overweight, that will cause heavy flow because estrogen is a fertilizer," she says. "Fat cells produce estrogen, which leads to a thicker (uterine) lining." Because the uterine lining is shed during your period, thicker lining equals heavier flow.

If a heavy period persists for more than one month, it is time to see the doctor because it could indicate other health issues.

Williams lists some of the possible causes as thyroid disorders (from 30s onward), polyps on the uterus, a bleeding disorder (potential cause for young girls with heavy flow) or adenomyosis.

"Adenomyosis is very common cause," Williams says. Adenomyosis is a condition in which endometrial tissue grows into the muscular walls of the uterus. "Instead of 5 to 7 milliliters (of lining) to shed, the pockets are 1 to 2 centimeters."

Hyperplasia, an abnormal thickening of the uterine lining, is another common cause of heavy periods. Though often begin, it can be a precancerous disorder.

As with heavy flows, a missed period can have underlying health factors. Pregnancy is the most common cause of a missed period, Blevins says. But for women who can rule out that possibility, there can be other causes.

In some cases, high levels of stress may disrupt your menstrual cycle. Excessive exercise could cause periods to stop for a while. Extreme weight loss and eating disorders can affect your cycles, as well. Another cause could be polycystic ovary syndrome, which occurs when a hormone imbalance interferes with normal ovulation.

"If it's occasionally you miss a month or two, you shouldn't be concerned," Williams says.

The onset of menopause can be another reason for missed periods.

"Menopause, which is defined by no menses for 12 months, usually happens around age 51," Williams says. "Bleeding after menopause is a matter of concern and should be evaluated by a health care professional."

The important thing to remember when confronted with an irregular period is to not panic. Just note any inconsistencies with your regular cycle, and consult your doctor if they happen again.

Additional sources: Mayo Clinic, Johns Hopkins, ARA Content