24 Nov 7 Possible Causes of Irregular Menstruation Every Month
7 Possible Causes of Irregular Menstruation Every Month
By Island Hospital | Nov 24, 2025 3:16:57 PM
Having your period is one of those things to expect will happen to you every single month, for 30 or so years of your life. It is just part of the deal of having a female reproductive system.
For some, though, their monthly flow is unpredictable. Even for the lucky ones who get it like clockwork, irregularity strikes every now and then.
But you are not pregnant, and you are nowhere near menopause, so what is the deal?
In this article, we’ll help you understand the common causes of irregular menstruation and guide you on what to do next.
What Causes Abnormal Menstruation (Periods)?
1. Stress and lifestyle factors
Stress can cause something called anovulation, when your body does not release an egg every month like it is supposed to. It can suppress the hormones that regulate ovulation, or the release of an egg from one of the ovaries. If ovulation does not happen, a period will not happen either.
Gaining or losing a significant amount of weight, dieting, changes in exercise routines, travel, illness, or other disruptions in a woman’s daily routine can have an impact on her menstrual cycle.
2. Extreme Exercise
Intense or excessive exercise has been shown to interfere with the hormones responsible for menstruation. Working out for hours a day may put your periods on hold. Your body perceives excess exercise as an extreme stressor. Cutting back on your training and increasing your calorie count can help restore your periods.
3. Medications
Many medications can all cause irregular bleeding and in some cases make your period go away altogether and it may change your bleeding pattern, too.
Birth Control Pills
Birth Control Pills contain a combination of the hormones oestrogen and progestin (some contain progestin alone). The pills prevent pregnancy by keeping the ovaries from releasing eggs.
Whenever you start a new type of oral contraceptive or go off another, it can make your period irregular for up to a few months as your body adjusts to its new, pill-directed cycle. Also, many birth control pills have very low oestrogen content, which can cause irregular bleeding.
Going on or off birth control pills can affect menstruation. Some women have irregular or missed periods for up to six months after discontinuing birth control pills. This is an important consideration when you are planning on conception and becoming pregnant.
Other Medications
Anticoagulants (blood thinners) like heparin or warfarin can make your period heavier. Some antipsychotics, antidepressants, and the drug methadone can also cause irregular delayed periods. If a new medication seems to be messing with your cycle, talk about it with your prescribing doctor.
4. Existing medical conditions
Polycystic ovarian syndrome (PCOS)
Unpredictable or irregular delayed periods are a hallmark sign of polycystic ovary syndrome (PCOS), a hormonal imbalance that interferes with the body’s ability to ovulate normally (anovulating). In PCOS, the ovaries make large amounts of androgens, which are male hormones.
Small fluid-filled sacs (ovarian cysts) may form in the ovaries. These can often be seen on an ultrasound. The hormonal changes can prevent eggs from maturing, and so ovulation may not take place consistently.
Sometimes a woman with PCOS will have irregular periods or stop menstruating completely. In addition, the condition is associated with obesity, infertility, and hirsutism (excessive hair growth and acne).
This condition may be caused by a hormonal imbalance, although the exact cause is unknown. If you begin to skip periods completely, it could be a sign of PCOS. PCOS is also the most common cause of infertility in women, yet millions have it without knowing — so seeking treatment sooner rather than later is a smart part of family planning.
About 1 in 10 women with irregular menstrual cycles has PCOS.
Endometriosis
The endometrial tissue that lines the uterus breaks down every month and is discharged into the pelvis with the menstrual flow. Endometriosis occurs when the endometrial tissue starts to grow outside the uterus.
Often, the endometrial tissue attaches itself to the ovaries or fallopian tubes; it sometimes grows on the intestines or other organs in the lower digestive tract and in the area between your rectum and uterus. Endometriosis may cause abnormal bleeding, cramps, or pain before and during periods, and painful intercourse.
Thyroid Disorder
Such as hyperthyroidism (hy-pur-THY-roi-diz-uhm). Hyperthyroidism, or overactive thyroid, causes your thyroid to make more thyroid hormone than your body needs. Hyperthyroidism can also cause fewer and lighter menstrual periods than normal.
Thyroid disorders can cause irregular periods if blood levels of the thyroid hormone go too low or too high. Other health conditions that may cause an irregular cycle include sexually transmitted diseases, diabetes, fibroids, eating disorders, and endometriosis.
5. Benign Tumors and Other Growths
Certain harmless growths can crop up in your genital tract and affect your bleeding.
You might have polyps in the uterus or the cervix, for example. You could also have uterine fibroids — growths that are not cancerous but can cause pain and bleeding. Uterine polyps are small benign (noncancerous) growths in the lining of the uterus.
Uterine fibroids are tumors that attach to the wall of the uterus. There may be one or several fibroids that range from as small as an apple seed to the size of a grapefruit. These tumors are usually benign, but they may cause heavy bleeding and pain during periods. If the fibroids are large, they might put pressure on the bladder or rectum, causing discomfort.
6. Menopause (Perimenopause)
Perimenopause is the transition phase before you enter menopause. It usually begins in your 40s, but can occur earlier. You may experience signs and symptoms lasting from 4 to 8 years, beginning with changes to your menstrual cycle.
During a normal menstrual cycle, the levels of the hormones oestrogen and progesterone increase and decrease in a regular pattern. Ovulation occurs in the middle of the cycle, and menstruation occurs about 2 weeks later.
During perimenopause, hormone levels may not follow this regular pattern. As a result, you may have irregular bleeding or spotting. Some months, your period may be longer and heavier. Other months, it may be shorter and lighter. The number of days between periods may increase or decrease. You may begin to skip periods.
7. Premature Ovarian Insufficiency
This condition occurs in women under age 40 whose ovaries do not function normally. The menstrual cycle stops, similar to menopause.
This can occur in patients who are being treated for tuberculosis or cancer with chemotherapy and radiation, or if you have a family history of premature ovarian insufficiency or certain chromosomal abnormalities. If this condition occurs, see your physician.
Interested to learn more? Check out our article on 10 common women’s health issues.
When Is a Period Irregular?
Your menstrual cycle is not always like clockwork. While some women get their periods right on schedule every 28 days, other women’s cycles are not so predictable.
A normal menstrual cycle lasts 28 days, plus or minus seven days. Menstrual bleeding is considered irregular if it occurs more frequently than every 21 days or lasts longer than 8 days. Missed, early, or late periods are also considered signs of an irregular cycle.
Period irregularities are very common and chances are you will experience them at one time or another during your reproductive years. “Irregular” can refer to the schedule, frequency, or duration of your period.
It can also be about the amount of bleeding you experience, and/or the amount of pain you feel during that time of the month.
To determine whether your menstruation schedule is irregular, count from the last day of your previous period and stop counting on the first day of your next. Repeat this for three months.
Periods as either “normal” or “abnormal” based on three criteria:
- how regular your cycles are,
- how long the bleeding lasts, and
- how much you are bleeding.
If your menstrual cycle is irregular from time to time, it is probably no big deal.
When Should You Be Concerned About an Irregular Period?
A missed or irregular period may be the first clue that you have a condition that needs medical attention.
An irregular cycle can also make it more difficult to get pregnant, especially if you are not ovulating every month. Your doctor can run tests to see if you are ovulating. Women with irregular periods who are trying to have a baby are sometimes prescribed fertility drugs to increase ovulation.
While it is possible to get pregnant on your own if you have irregular periods, it is still a good idea to be checked out by a doctor just to make sure that nothing serious is going on.
For most women, their period then lasts from four to seven days. Your “normal” will likely be different from your friends, and that is perfectly okay.
“The thing I always tell patients is that it is really about your own perspective. If it feels like it’s abnormal and it is bothering you, then it is,” says Dr Mahalakshmi Ratnavale, of Island Hospital’s Obstetricians and Gynaecologists.
Not sure which health screening to get? We cover all this and more in our article on 8 essential health screenings for women.
Evaluation of Irregular Periods
History
There are often clues about the cause of amenorrhea in a woman’s personal and family medical history.
A woman should mention if she had any health problems during infancy or childhood, when her first period started (if there was a first period), and how frequently periods have occurred since. If known, the woman should also mention if there is any family history of irregular menstrual periods.
Other important points include the presence of discharge from the breasts, hot flashes, adult acne, facial or chest hair, and headaches or impaired vision. The doctors will also ask about any medications, herbs, and vitamins used; recent stress; recent gynecologic procedures; changes in weight, diet, or exercise patterns; and illnesses.
Physical Examination
During the physical examination, the doctor will examine the face, neck, breasts, and abdomen. A pelvic examination will also be performed.
Testing
Depending upon the individual, the doctor may order blood tests. Because pregnancy is the most common cause of secondary amenorrhea, a urine pregnancy test is usually recommended for women whose menstrual periods have stopped. Blood tests to measure hormone levels will also be ordered.
What Can I Do if My Period is Irregular?
- Mark on a calendar the dates when each period starts and stops. This information can help your healthcare provider make a correct diagnosis. Take the calendar to your appointment. Tracking your menstrual cycle is important. Consider using a calendar or app on your smartphone or tablet computer to help track irregularities in your menstrual cycle.
- Eat healthy foods and keep your weight steady*. If you are overweight, a balanced diet and regular exercise will help you lose weight slowly. If you are underweight, make sure you are getting enough nutrition.
- If you follow a strenuous exercise programme, consider cutting back until your periods come back. If you do not want to cut back on your exercise, see your healthcare provider to see if you need to cut back on exercise, eat more calories, or need treatment.
- If you have had sex, get a pregnancy test if your period is 5 or more days late. You might want to rule out pregnancy first. Take a home pregnancy test first.
- See if you can get some counseling if you are feeling stressed out.
*Note: Talk with your healthcare provider if you are not sure what your proper weight should be, or if others are worried about your weight. A nutritionist may also be able to give you helpful advice.
Schedule a Consultation at Island Hospital
A couple of irregular periods per year are usually nothing to worry about.
Any more than that and any changes should always be discussed with a doctor to be sure of an ovulation problem, because irregular periods can signal underlying medical conditions and potentially have long-term health consequences.
If you call your gynecologist, he or she may advise you to wait a few more cycles to see if the irregularity persists. If it does, then it’s time to see your doctor.
At Island Hospital, our gynecologists will be able to determine the cause of your irregular periods and help you figure out a treatment course to get your menstrual cycle back on track.
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