Almost every woman has a period that arrives early, late or heavier than usual now and then. An irregular menstrual cycle is different: a pattern of periods that come too often, too rarely, unpredictably, or with bleeding that is much heavier or longer than normal for you. It is common, and in many cases the cause is straightforward and treatable. But because irregular bleeding can also be the first sign of a hormonal condition, a thyroid problem or a change in the lining of the uterus, it deserves a proper evaluation rather than guesswork.
Our gynecologists see irregular cycles in women of every age, from the first years after periods begin through the transition to menopause. The goal of the visit is simple: find out why your cycle has changed and match the treatment to that cause.
What counts as normal and what counts as irregular
The average cycle, counted from the first day of one period to the first day of the next, is about 28 days, but a normal cycle can range from 21 to 35 days, according to the NICHD. Bleeding usually lasts two to seven days. Some variation from month to month is expected.
Cleveland Clinic describes cycles as irregular when periods come fewer than 21 or more than 35 days apart or last longer than seven days. Other patterns worth attention include missing three or more periods in a row, bleeding or spotting between periods or after sex, bleeding heavy enough to soak through protection quickly or pass large clots, and any bleeding after menopause.
Common causes of irregular periods
The first possibility we always rule out is pregnancy, including in women who use contraception. After that, the most common causes fall into a few groups.
Hormonal and ovulation problems are the largest group. Polycystic ovary syndrome causes infrequent or absent ovulation, often with acne, excess hair growth or weight gain. An underactive or overactive thyroid can shorten or lengthen cycles, and a raised prolactin level, sometimes from a medication or a small benign pituitary growth, can stop periods. Stress, significant weight loss or gain, and intense exercise can switch off ovulation for months. In the forties, perimenopause brings cycles that become shorter, longer or heavier as ovulation becomes less regular.
Structural causes inside the uterus, such as polyps and fibroids, tend to cause heavy periods or bleeding between periods. Bleeding disorders, including von Willebrand disease, are an often-overlooked cause of heavy periods, especially when they have been heavy since the teenage years. Medications also matter: starting, stopping or changing birth control, a hormonal IUD, blood thinners and some psychiatric medications can all change the pattern of bleeding.
How we evaluate irregular periods at NYMD Center
We begin with a detailed history: when the change started, how often and how heavily you bleed, pain, pregnancy plans, weight changes, stress, exercise, medications and symptoms such as acne, hair growth, fatigue, heat or cold intolerance, or milky nipple discharge. A pelvic exam follows.
Testing is targeted to what the history suggests. Most women need a pregnancy test, a TSH to check thyroid function, a prolactin level and a complete blood count to look for anemia from heavy bleeding. When PCOS is suspected we add androgen levels such as testosterone. If periods are heavy, clotting studies may be part of the workup, as MedlinePlus notes. A pelvic ultrasound, done in our office, looks for fibroids, polyps, a thickened lining and the multiple small follicles typical of PCOS.
Some women need a sample of the uterine lining. We recommend endometrial sampling for women 45 and older with abnormal bleeding, and for younger women with risk factors for overgrowth of the lining, such as years of infrequent periods, obesity or bleeding that persists despite treatment. The sample is taken in the office through a thin tube and takes only a few minutes. When the ultrasound suggests a polyp or fibroid inside the cavity, hysteroscopy lets us look directly inside the uterus and often remove it at the same time.
Treatment follows the cause
There is no single treatment for irregular periods, because the right answer depends entirely on why they are irregular and on whether you are hoping to become pregnant.
Treating an underlying condition
When a thyroid problem or high prolactin is the cause, treating it usually restores a regular cycle. Our internal medicine physicians manage thyroid disease alongside us. For PCOS, weight loss of even a modest amount can restart ovulation, and medication can help when it does not. When stress, under-eating or heavy training is responsible, adjusting those factors is the treatment.
Hormonal regulation
For many women, combined birth control pills, a progestin, or a levonorgestrel IUD regulate bleeding, reduce heavy flow and protect the lining of the uterus from overgrowth when ovulation is infrequent. Our contraception and IUD page reviews those options. Their main trade-off is that they prevent pregnancy, and some women have spotting in the first months.
Non-hormonal options and procedures
For heavy periods, non-hormonal medications taken only during the period can reduce blood loss, and iron replaces what has been lost. Polyps and some fibroids can be removed through hysteroscopy. Larger fibroids may be treated with medication, uterine fibroid embolization or surgery, depending on their size and location and your plans for pregnancy.
What to expect at your visit
Before your appointment, track your bleeding for two or three cycles if you can, noting the start and end dates and how heavy each day is. A period-tracking app works well. At the visit we review that record, take your history, examine you and order the tests that fit your situation. Many results are back within days, and we then meet again to explain the cause and agree on a plan.
When to seek care urgently
Go to an emergency room or call 911 if you are soaking through a pad or tampon every hour for several hours in a row, if you feel faint or dizzy or pass out, or if you have bleeding with a known or possible pregnancy, especially with one-sided pelvic pain. These can signal dangerous blood loss, a miscarriage or an ectopic pregnancy.
Questions patients ask
How irregular is too irregular?
A normal cycle ranges from about 21 to 35 days, with bleeding lasting up to about seven days. It is worth an evaluation if your periods come more often than every 21 days or less often than every 35, if you miss three or more in a row, if bleeding lasts longer than seven days, or if you bleed between periods, after sex or after menopause.
Can stress really make my period late?
Yes. Significant stress, rapid weight loss, under-eating and intense training can all suppress the hormonal signals that trigger ovulation, delaying or stopping periods. It is still important to rule out pregnancy, thyroid problems, high prolactin and PCOS before settling on stress as the explanation, and a simple set of blood tests usually does that.
Does an irregular cycle mean I will have trouble getting pregnant?
Not necessarily, but irregular cycles often mean you are ovulating less often, which can make timing harder. Causes such as PCOS, thyroid disease and high prolactin are treatable, and treating them frequently restores regular ovulation. If you are trying to conceive, tell us at the first visit, because it changes which treatments we recommend.
Why would I need a biopsy of the uterine lining?
When ovulation is infrequent or bleeding is abnormal, the lining of the uterus can overgrow. We recommend sampling for women 45 and older with abnormal bleeding and for younger women with risk factors such as years of infrequent periods or obesity. The sample is taken in the office through a thin tube in a few minutes, and most results are reassuring.
Are irregular periods normal in my forties?
Often, yes. In perimenopause, ovulation becomes less regular and cycles may become shorter, longer or heavier. But fibroids, polyps and changes in the uterine lining also become more common at this age, so new heavy or irregular bleeding in your forties should be evaluated rather than assumed to be perimenopause.