A late period can be cause for concern to some. It might be due to life stresses, but could also signal a health problem. Periods can be late due to peri-menopause, premature menopause, thyroid problems or pregnancy — or, it could be due to long-distance running or overtraining.
Long-distance running can cause metabolic stress, resulting in a delayed or absent period. Excessive exercise puts a lot of stress on a woman's body — so much so, that your hormones get out of whack and your period is delayed or disappears altogether for months on end.
Running a moderate amount, such as 30 to 45 minutes several days per week, is unlikely to cause your period to come late. However, if you're obsessed with running and go dozens upon dozens of miles per week without proper recovery, it can interfere with your cycle. Combine excessive running with restrictive dietary habits and low body fat, and you might just have found the reason why you're still waiting on Aunt Flo.
Athletic amenhorrea describes the condition experienced by many female athletes in which their intense, athletic lifestyles cause a cascade of hormonal changes so their periods are intermittent, or absent. It's often due to excessive exercise stress and can have a psychological component, too, especially if you're training for a big event or meet.
When your period's not just late, but absent for months — or even years — at a time, you could be suffering from the female athlete triad. The female athlete triad describes three distinct conditions: disordered eating, amenorrhea and low bone density.
Read More: Amenorrhea Side Effects
Consider Your Eating Habits
Exercise, specifically running, doesn't mean you're on route to the female athlete triad, nor does one late period. If you're driven to succeed in your running, however, and limit your food intake to get lean so you can run farther and harder, there's reason to be concerned.
Restricting your caloric intake, especially when you're burning lots of calories in your daily runs, puts your body into a state of alarm — so much so, that you're predisposed to menstrual abnormalities. Your system feels it doesn't have the reserves necessary to support a fetus were you to get pregnant, and your period — meaning your fertility — goes away.
If you're a runner — and especially if you're training for a race or competition — make sure your fuel plan works for your health, not against it. Eat enough calories to keep your body at a healthy weight.
See a Doctor
If you're a runner who is older than 16, but haven't yet started menstruating, consult a doctor. Women of any age who have missed three consecutive periods, or experience them more than 35 days apart, should also seek medical advice.
Read More: Reasons for a Missed Period and Not Pregnant