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Top Reasons Your Period Is Irregular

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Written by Andrew Le, MD.
Medically reviewed by
OBGYN at Mercy Health - St Elizabeth Youngstown Hospital
Last updated April 19, 2024

Irregular period quiz

Take a quiz to find out what's causing your irregular period.

An irregular period is when your cycle is too short or too long. It can also cause spotting in between periods, or be very heavy. It’s usually caused by hormonal imbalances.

Irregular period quiz

Take a quiz to find out what's causing your irregular period.

Take irregular period quiz

What is an irregular period?

Irregular periods are very common, with most women having an irregular period once in a while. It’s usually because of a disruption in the hormones that regulate menstruation.

The average adult menstrual cycle lasts 28 days, but anywhere between 21–35 days is considered regular. Bleeding usually lasts 4–7 days, causing about 3 tablespoons of blood loss. Menstrual cycles are most regular between the ages of 20–40. Irregular periods are more common in the first few years after you get your first period and in the last 10 years before menopause.

But every woman is unique. Some women get their period on the same exact day every month, while for others, it varies from month to month.

Pro Tip

Most women will experience an irregular period at least once in their life. It is actually uncommon to have only had regular periods every single month of your menstrual history. —Dr. Jessica Katz

Symptoms of an irregular period

Irregular menstruation can mean a missed, delayed, or not regular period. Signs of an irregular period include one that lasts for more than 7 days, cycles that occur more often than every 21 days or less often than every 35 days, and bleeding so heavy that you lose more than 5 tablespoons of blood.

Signs an irregular period is serious

Signs that an irregular period is a cause for concern include:

  • Missing your period for more than 3 months in a row, which can lead to precancerous or cancerous endometrial cells.
  • Bleeding heavily for more than 7 days, especially if you also have symptoms of anemia (shortness of breath, dizziness, light-headedness, and pale skin) due to prolonged blood loss.
  • Bleeding when you’re pregnant.
  • Having symptoms like abnormal vaginal discharge or odor, unexplained weight loss or weight gain, and fever.
  • Having pain before and/or during your period that’s severe enough to cause you to miss school or work.
  • Bleeding that occurs after menopause, which may be a sign of uterine cancer (also called endometrial cancer).
  • Bleeding after intercourse, which may be a sign of cervical cancer.

Make an appointment with your ob-gyn if you notice any of these signs or any other worrisome issues. You should go to the ER or an urgent care center immediately if you experience symptoms of anemia.

Dr. Rx

When someone has an irregular period, it is very important for me to understand her menstrual history. How old was she when she got her first period? How many days are usually between periods? Does she consider her periods heavy? How many pads or tampons does she have to change a day? Does she experience terrible cramping/pelvic pain? Has she always had irregular periods or is this something new? —Dr. Katz

Common causes

1. Polycystic ovarian syndrome (PCOS)

Polycystic ovarian syndrome is one of the most common causes of irregular periods. It occurs when the ovaries make a large amount of androgens, a male hormone. This causes a hormonal imbalance that triggers the formation of multiple cysts in the ovaries, which prevents the ovaries from regularly releasing eggs. Many women with PCOS have irregular periods or stop menstruating completely.

Common: PCOS affects anywhere from 5–15% of women of reproductive age [Source: National Institutes of Health].

Other symptoms you may have:

  • Weight gain
  • Infertility
  • Excess facial and body hair (hirsutism)
  • Thinning hair on the head
  • Acne

Treatment and urgency: If you’ve missed your period for 3 months in a row or have had irregular periods for 6 months in a row, see your ob-gyn. Treatments include:

  • Ovulation-stimulating medications if you are trying to get pregnant
  • Weight loss
  • Birth control pills
  • If necessary, metformin to control high blood sugar. Women with PCOS are often insulin resistant, leading to higher sugar levels in the blood.

2. Thyroid issues

The thyroid helps control your menstrual cycle. Irregular periods may occur when the thyroid produces too little thyroid hormone (hypothyroidism) or too much (hyperthyroidism). One of the first signs of a thyroid problem in women may be skipped or no periods or much heavier and longer periods than usual.

Common: More than 12% of the U.S. population will develop a thyroid condition in their lifetime. Women are 5 to 8 times more likely to have thyroid problems than men.

Other symptoms you may have:

Hypothyroidism and hyperthyroidism have different symptoms but include:

  • Weight loss or weight gain
  • Cold or heat intolerance
  • Brittle, dry skin or warm and clammy skin
  • Constipation or diarrhea
  • Sleep disturbances and fatigue
  • Dry hair and hair loss
  • Slow heart rate or heart palpitations

Treatment and urgency: If you have symptoms of a thyroid issue, see your doctor. Hypothyroidism is treated with thyroid hormone. Hyperthyroidism is treated with either a daily antithyroid medication, surgery, or radiation.

3. Pelvic inflammatory disease

Pelvic inflammatory disease (PID) is an infection of the female reproductive tract. It’s caused by a bacterial infection, usually a sexually transmitted infection like chlamydia. Bacteria enters the vagina and spreads to the uterus and fallopian tubes, leading to PID. Left untreated, PID can cause complications such as pelvic adhesions, chronic pain, and infertility.

Uncommon: It occurs in about 10–20 out of 1,000 women.

Other symptoms you may have:

Treatment and urgency: Some women may have only mild pelvic pain and vaginal discharge, but you should still see your doctor in the next 1–2 days if you have any symptoms of PID. If the pain is severe, you may need to go to an urgent care center or the ER, especially if you also have a fever.

While treatment cannot undo any damage that PID already caused to your reproductive system (such as adhesions or scar tissue), antibiotics can relieve your symptoms and prevent any long-term complications.

4. Perimenopause

Perimenopause is the time in a woman’s life when the body transitions to menopause. It usually begins in your mid to late 40s. As your ovaries produce less estrogen, your period might become irregular. Periods may occur more frequently or less than once a month, be heavier or lighter than usual, or shorter or longer than usual.

Common: All women experience it.

Other symptoms you may have:

Treatment and urgency: Irregular periods that occur during perimenopause are normal and expected so they don’t require treatment. But depending on the severity of symptoms, your doctor may recommend staying on or starting birth control pills (or other hormonal contraception) to help regulate periods.

You should see your ob-gyn if you have any of the following symptoms, which may be a sign of other issues:

  • Your bleeding is unusually heavy for you
  • You’re soaking through one or more pads or tampons an hour
  • You get your period more often than every 3 weeks
  • Your period lasts longer than usual
  • You bleed during sex or between periods

5. Uterine and cervical cancer

Both uterine cancer and cervical cancer can cause abnormal bleeding. If you’ve gone through menopause and experience bleeding, the chance that you have cancer is much higher.

Risk factors for uterine cancer include obesity, PCOS, starting your period at an early age, an imbalance of the hormones estrogen and progesterone, genetics, and never giving birth. Risk factors for cervical cancer include having several sexual partners, HPV infection, and smoking.

Uncommon: Cervical cancer is uncommon, affecting about 15,000 women each year. The prevalence of uterine cancer is estimated at 66,570 per year. [Sources: American Cancer Society; American Society of Clinical Oncology]

Other symptoms you may have:

Urgency and treatment: Although cancer is less likely to be the cause of irregular periods, you should see your ob-gyn to rule it out. Treatment for uterine cancer and cervical cancer may include surgery, radiation, and chemotherapy.

6. Extreme weight loss or eating disorders

Losing a lot of weight, through extreme dieting or intense exercise can cause irregular periods and, in some cases, stop them altogether. Having an eating disorder such as anorexia or bulimia can also cause irregular periods. When the body doesn’t have enough energy, the hormonal cycle that regulates your periods is disrupted.

Common: About 30 million Americans have these disorders. [Source: National Association of Anorexia Nervosa and Associated Disorders]

Other symptoms you may have:

  • Cognitive problems such as difficulty concentrating
  • Difficulty sleeping
  • Mood changes
  • Dizziness
  • Hair loss
  • Fatigue
  • Osteopenia (low bone density)
  • Night sweats

Treatment and urgency: The most effective treatment is returning to a healthy weight, which should cause your cycle to return to normal. It may take up to 6 months for your period to become regular once you reach a healthy weight. You may be referred to a therapist, psychiatrist, or eating disorder program if you have an exercise disorder or eating disorder.

7. Stress

When you’re under stress, your body produces a hormone called cortisol that can cause delayed or light periods. It’s difficult to say how much stress is too much because tolerance levels vary depending on the person, but the higher the cortisol levels, the more likely you are to have an irregular period.

Common: Most people experience stressors and it is common for your period to be irregular at some point in your life.

Other symptoms you may have:

  • Acne
  • Headaches
  • Fatigue
  • Insomnia
  • Rapid heartbeat
  • Sweating

Treatment and urgency: See your ob-gyn after three missed or dramatically different periods. They will rule out other conditions that could be causing your menstrual changes. Try to find ways to reduce stress, like exercising, eating a healthy diet, and meditation. The birth control pill may also be prescribed to correct the hormonal imbalance and regulate your cycles.

8. Hormonal birth control

Going on or off birth control can lead to abnormal bleeding. Some women have irregular or no periods for up to 6–12 months after stopping hormonal contraceptives (it’s more common with the Depo-Provera injection). Women who forget to take their contraceptive will have irregular bleeding or spotting. If your birth control pills contain only progestin or you use an IUD or implant, you may have abnormal spotting or bleeding for several months. Most people with the Mirena IUD stop having their period 6 months after insertion.

Very common

Treatment and urgency: If the symptoms bother you, your doctor can switch the amount of hormone or type of contraception.

9. Premature ovarian failure (POI)

If you are under age 40 and your period has become infrequent or has disappeared, it may be a sign of premature ovarian failure or “early menopause.” This is when your ovaries stop releasing eggs before age 40. Premature ovarian failure may be genetic, or caused by a chromosomal abnormality or cancer treatments.

Rare: The risk of POI before 40 years of age is 1% [Source: Menopause Review]

Other symptoms you may have:

  • Hot flashes
  • Night sweats
  • Anxiety, depression, or mood swings
  • Concentration or memory problems
  • Lower sex drive
  • Difficulty sleeping
  • Vaginal dryness

Treatment and urgency: See your ob-gyn if you’ve missed several periods in a row and if you are experiencing any of the symptoms of POI. A lab test can show if your hormone levels are in the menopausal range. It is important to know if your body no longer makes estrogen, so you can supplement it if necessary to improve your overall health.

10. Endometrial polyps

Endometrial polyps are small growths in the uterine lining or on the cervix. Polyps commonly affect a woman’s period, causing irregular cycles. They grow in response to estrogen. Risk factors for endometrial polyps include being menopausal or postmenopausal, obesity, hypertension, and taking tamoxifen, a drug that treats breast cancer. The vast majority of endometrial polyps are not cancerous.

Common: Endometrial polyps develop in 16–34% of women.

Other symptoms you may have:

  • Heavy or prolonged periods
  • Spotting between periods
  • Spotting after intercourse
  • Miscarriage or infertility

Treatment and urgency: Endometrial polyps are usually diagnosed using a special type of ultrasound or by looking into the uterus with a camera. Polyps can be removed surgically.

Pro Tip

Even if you are on birth control, the most common reason for an irregular period is pregnancy! It should always be ruled out first. I have had many patients with the diagnosis of PCOS who have never had a period without medical intervention get pregnant because they weren’t on birth control, thinking they would never be able to get pregnant. —Dr. Katz


Can you get pregnant if your period is irregular?

Yes, you can still get pregnant even if your period is irregular. But having unpredictable periods or skipping periods makes it harder to track when you will be ovulating, which is when you’re most fertile. Irregular periods also make it difficult to know if you are pregnant because you won’t know when you should be getting your period.

How irregular periods change during aging

It’s very common to have irregular periods before the age of 20 and after the age of 40. During the first few years after your first period, it’s normal to have irregular periods because the body’s system that regulates periods (the hypothalamic pituitary ovarian axis) is still maturing. By age 20, most women will have regular menstrual cycles.

Women usually go through the perimenopausal transition in their 40s, which causes irregular periods. As you approach menopause, periods get further apart until they stop for good. A woman is in menopause when she hasn’t had a period for a year.

How to track your periods

If anything about your menstrual cycle has changed, start keeping an up-to-date record of exactly when your period begins and ends, including the amount of flow and whether there were large blood clots.

It’s also a good idea to keep track of symptoms like bleeding between periods and pelvic pain. If you’re sexually active and haven’t gone through menopause, consider taking a home pregnancy test. If your cycle is still not normal after 3 months, you may want to call your doctor.


Ways to regulate your period include:

  • Taking hormones such as estrogen and progesterone. These hormones are found in different methods of birth control, including the pill, patch, and ring. Or you may take progesterone alone, which is available in pills, injections, an implant, and intrauterine devices (IUDs). The Mirena IUD works extremely well in women whose period or bleeding is not normal.
  • A non-hormonal medication called Lysteda may be recommended if you also have excessive menstrual bleeding.

Ways to prevent irregular periods

  • Try to maintain a healthy weight and lifestyle. If you want to lose weight, do it gradually and with the help of professionals. Exercise moderately and eat nutrient-dense foods.
  • If you’re an athlete, try to cut back on very long or intense workouts.
  • Try relaxation techniques to help with stress and with getting enough sleep.
  • Take prescribed birth control correctly. If you are forgetting to take a daily birth control pill, ask your doctor if you should switch to the patch, vaginal ring, implant, or an IUD like Mirena.
  • Use condoms to prevent STDs.
  • See a doctor for regular check-ups and don’t hesitate to bring up any questions or concerns you may have.
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OBGYN at Mercy Health - St Elizabeth Youngstown Hospital
Dr. Katz is a board-certified OBGYN, who is thrilled to have fulfilled a life-long dream of becoming a physician and helping women of all ages and backgrounds be in the best health possible and get access to top level care. She received her undergraduate degree in anthropology from the University of Michigan (2006) and graduated from Des Moines University of Osteopathic Medicine and Surgery (2011)...
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