If you just started your period or are age 45 or older, it's normal to skip periods.
"But if a woman who has been menstruating regularly misses a period, she needs to know why and needs to realize it carries a risk of bone loss," says Prior.
Thinning bones can lead to osteoporosis and eventually bone fractures. While missing a period now and then isn't a major concern, you should tell your doctor if it happens frequently. The problem may be that you don't weigh enough to be menstruating properly.
Speak to your doctor if you're having heavier-than-usual periods, especially if they're outside of your regular cycle. Heavy menstruation may lead to iron deficiency anemia, which can play havoc with your productivity, feelings of self-worth and ability to exercise, says Prior.
According to Feldman, increased menstrual flow may be a result of infection or a symptom of hypothyroid, a condition in the thyroid gland that controls the body's metabolism. There's also a small chance that heavy menstruation outside of your regular cycle might be a sign of uterine cancer.
Change in your period pattern
Be mindful of your monthly flow, including how it usually feels and how strong your cramps normally are. If your menstrual cycle has been delayed and heavy bleeding follows, it might mean that you've had a "spontaneous miscarriage and need to see a doctor," explains Prior.
Some women brush off bleeding outside of their regular period days, excusing their bodies by saying they were simply "stressed out" that week. However, "stress doesn't really cause bleeding," says Feldman. "Bleeding outside of your cycle isn't generally normal and you should talk to your doctor about that."
Having your period outside of your regular cycle could be a sign of a thyroid problem or a sexually transmitted infection or tubular pregnancy if you have had unprotected sex.