What counts as an irregular menstrual cycle
The cycle is counted from the first day of one period to the first day of the next. For many women it lasts about 28 days, but intervals of roughly 21 to 35 days are also considered normal. If periods come less or more often, the cycle length varies a lot from month to month, periods stop, or they become very heavy or last more than a week, the cycle is called irregular. A single change, for example after stress or an illness, is usually not a cause for alarm. See a doctor when it keeps happening for several months.
A missed period
The first thought for a woman who has sex is pregnancy, so start with a test. If the test is negative and you have had no period for more than a few weeks, you need a consultation. If the delay comes with lower abdominal pain, spotting, weakness or fainting, do not put off a visit: that is how an ectopic pregnancy can show itself. For more on pain, see Abdominal pain, and for discharge, Vaginal discharge.
Infrequent and frequent periods
An interval longer than 35 days or shorter than 21 days is most often hormonal. The causes include polycystic ovary syndrome, thyroid disease and high prolactin. These conditions often come with weight gain, excess hair growth, acne or hair loss, and a gynecologist or a gynecologist-endocrinologist looks into them.
Periods disrupted by stress, weight and exercise
The cycle is sensitive to stress, rapid weight loss or gain, strict diets, very intense training, travel across time zones and illness. It usually returns once the cause is gone, but if it has not within 2 to 3 months, get checked.
Periods with hormonal medicines and after childbirth
Hormonal contraception, including pills, injections and a hormonal coil, can change the nature of periods, even to the point of having none. The cycle can also shift after stopping contraception, after childbirth and while breastfeeding. If the changes bother you or raise questions, discuss them with the doctor who prescribed the method.
Irregular periods in teenagers and after 45
In the first years after periods begin, the cycle is often irregular as the body tunes its hormone system. But if there is no period by 15 or 16, or periods are very painful and heavy, have the girl seen by a gynecologist. After 45, cycle changes are often linked to approaching menopause, but heavy, long or in-between bleeding should be checked at any age.
Heavy and prolonged periods
If you need to change a pad more than once an hour, periods last longer than 7 days, come with clots, or you feel weak and dizzy, see a doctor. Over time, blood loss leads to anemia. If you suddenly feel much worse, call 112.
Irregular periods and pregnancy
For women planning a pregnancy, an irregular cycle makes it hard to tell when ovulation happens and can lower the chance of conceiving. If pregnancy has not happened within a year (six months after 35), see a doctor rather than waiting longer.
What you can do before the visit
- If pregnancy is possible, take a test.
- Keep a calendar: dates when periods start and end, how heavy they are, pain and spotting between them.
- Note your weight, changes in activity, medicines and contraception.
- Do not take hormonal medicines on a friend's or the internet's advice.
- With severe pain, heavy bleeding or weakness, do not wait for an appointment.
How a doctor looks for the cause
The doctor asks about the cycle, weight, stress and medicines, examines you and, if needed, orders a pregnancy test, blood tests for hormones and an ultrasound of the pelvis and thyroid. Treatment depends on the cause: sometimes a lifestyle change is enough, and in other cases medicine is chosen. Often no treatment is needed at all.