An irregular period can refer to a few different things, but it generally refers to a disruption in the number of days in a menstrual cycle. The norm for a menstrual cycle is 28 days; this means that the first day of menstruation is counted as day one, and a woman can then logically expect to start menstruating again on day 28, which will then start over as day one. In an irregular period, then, the menstrual cycle may be longer or shorter than 28 days, and some women may skip one month or more, and not menstruate at all.
In addition, an irregular period can refer to the type of period that a woman has. A period one month might be very heavy, whereas the next month might be very light. The causes of irregular periods can vary, and include dietary changes, excessive exercise, hormonal changes, pregnancy, irregular ovulation, birth control, or other types of medication. Some types of cold or cough medicines, for example, can cause an irregular period one month.
Excessive dieting, weight loss, or extreme exercise is a common cause of an irregular period, or the cessation of a period altogether. This is known as amenorrehea, and is frequently seen in people who suffer from eating disorders. Birth control pills can also cause the cessation of a period, as well as some other medications. Hormone irregularities can also cause irregular periods. One of the most common causes of a missed period is pregnancy, however, and it is often a woman's first indication that she is pregnant.
Some women also do not get a period, or have an irregular period, while breastfeeding. During menopause, many women will experience irregular menstrual cycles before they stop menstruating altogether. A number of other factors can cause an irregular cycle, such as high levels of stress, an illness such as the flu, or even travel. It is best to keep track of one's cycle for at least a few months before becoming concerned; irregular periods are quite common among many women.
If the irregular periods continue, however, it may be a good idea to visit a doctor. It is important to visit a doctor once a year for a gynecological exam anyway, so this is a good time to mention irregular menstrual cycles. This is especially true if one is attempting to get pregnant, and is having difficulties; a doctor will be able to perform tests to check fertility.