12 Less-Known Causes of Irregular Periods

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You know birth control, pregnancy, and certain health conditions can switch up your monthly cycle. But can alcohol affect your period — and what about smoking? These and more less-expected causes of irregular periods could be to blame, too.

01 of 13

Wondering Why Your Period Is Irregular?

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If your period changed — became heavier, lighter, longer, or less frequent — would you notice? Hopefully the answer is yes: Paying attention to irregularities in your cycle provides a clue into your overall health. While some issues, such as stress, may temporarily affect your period and resolve on their own, others may actually be serious health problems that need to be addressed.

"I always recommend patients download a period tracker app on their phone," says Eduardo Lara-Torre, M.D., an ob-gyn at Carilion Clinic in Virginia. "It's important to understand what's normal for you so you can identify when something isn't right," he adds. And take a look at these common causes of irregular periods, so you can begin tracking your cycle's changes ― addressing these menstrual changes early on can prevent them from getting worse, so you can sail smoothly through your monthly flow.

02 of 13

Overdoing the Alcohol

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Can alcohol affect your period? Turns out, frequent boozy nights out could leave you with more lasting effects than a string of killer hangovers. According to the National Institute on Alcohol Abuse and Alcoholism, chronic (the important factor here) heavy drinking can cause irregular periods. Still, a three-week study showed that a significant number of women who classified as "social drinkers," consuming about three drinks per day, also dealt with abnormal menstrual cycles, according to the Institute.

The reason this is one of the causes of irregular periods: Alcohol may temporarily increase levels of estrogen and testosterone, which may disrupt the normal hormonal fluctuations necessary for ovulation. As a result, your periods may become irregular or you may even skip them.

Researchers aren't sure how much alcohol it takes to disrupt your cycle — the quantity likely varies from person to person, but sticking to the guideline of one drink or less per day is the best way to keep your pinot from interfering with your period. (And if your bottle of red gets funky before you finish it, try one of these hacks to use up the leftover vino.)

03 of 13

A Serious Stressor

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You've heard that stress can mess with your cycle, but although they're not exactly good for you, daily hassles (you know: commuting, deadlines, presentations) are unlikely to be one of the causes of irregular periods. "It often takes a one-time extraordinarily stressful event to create an abnormal period," says Dr. Lara-Torre. Think: death of a family member, loss of your job, divorce, or illness.

There may be an evolutionary explanation behind this phenomenon: When you're focused on survival (whether the threat is a saber-tooth tiger or paying your mortgage) your body and brain shut down the hormones needed to make your body ovulate in order to prevent reproduction in a threatening environment, says Dr. Lara-Torre.

04 of 13

Excess Exercise

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Cool it in the weight room: Working out for hours a day may actually be your cause of irregular periods. Your body perceives excess exercise as an extreme stressor and may put the kibosh on the monthly hormonal symphony it's used to producing. "You need a certain amount of body fat to ovulate, so if your body fat dips too low you may stop ovulating," says Mary Jane Minkin, M.D., professor of obstetrics and gynecology at Yale School of Medicine. You may notice you don't get your period at all or you get it a few times per year on an unpredictable schedule. (If that doesn't convince you to lay off your daily 12-mile run every once in a while, these reasons will.)

05 of 13

Weight Gain or Loss

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Rapid weight gain, such as putting on 50 pounds over the course of a few months, can throw your hormones for a loop, making it one of the causes of irregular periods. "With weight gain, your ovaries start producing extra testosterone. This can prevent ovulation, so you may have very long cycles or skip your period altogether," says Dr. Minkin.

By the same token, extreme weight loss, especially as a result of an eating disorder such as anorexia or bulimia, also messes with your hormones and can even stop your periods altogether.

06 of 13


A woman dealing with cramping while laying on the couch

Can infection delay your period? While an infection won't impact your cycle on a hormonal level, it can cause bleeding and make you think you're getting your period more frequently than normal. "Bacterial infections, pelvic inflammatory disease, and sexually transmitted infections can cause the inside of your uterus to become inflamed and bleed," says Dr. Lara-Torre. "You'll still get your regular period, but you may bleed in between because of the infection," he continutes. Yikes.

You may even experience cramping because the uterus perceives bleeding as an irritant. If the bleeding seems random and you experience any other signs of an infection such as painful urination, pain or tenderness in your abdomen, pain or itching in your vagina, unusual discharge, fever, or vomiting, pay a visit to your gyno.

07 of 13

Antidepressants or Other Prescription Drugs

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One of the common causes of irregular periods, antidepressants and other medications can disrupt your cycle and make you skip periods or get them more frequently. "Many of these medications elevate a pituitary hormone called prolactin, which can alter other hormones in your body that regulate your cycle," says Dr. Minkin. (Hold on, can antibiotics make your birth control less effective?)

08 of 13

Shift Work

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Your late nights at the office could actually be switching up your cycle. In a study of 119,000 women, researchers found that those working evenings and nights had a 33 percent higher risk of menstrual problems, such as irregular periods and fluctuations in how long they lasted.

Plus, the more your work schedule fluctuates, the more likely you are to experience problematic periods. One study found that women who worked rotating shifts were 23 percent more likely to have very short cycles (less than 21 days) or very long ones (40 days or more) than those who followed a more set schedule (even if they worked nights), reports the journal Epidemiology. One explanation for this cause of irregular periods is that shift work disrupts your body's circadian rhythm, which controls a variety of biological functions — including your menstrual cycle.

09 of 13

Thyroid Disorder

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Irregularity in your cycle —especially amenorrhea, the terms for when periods stop for several months — can be the sign of an issue with your thyroid. Both over-productivity or under-productivity of the thyroid gland is strongly correlated with menstrual problems because the thyroid helps regulate the body's hormone production, according to the Office on Women's Health. Check with your doctor if you're seeing the red flag of a missed period, or if you have a family history of thyroid conditions that could be a cause of irregular periods. (Here's what you need to know about Graves' Disease, a disorder that leads to an overactive thyroid.)

10 of 13


A profile shot of a blonde woman smoking a cigarette
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Can smoking make your period irregular? For starters, period-havers who smoke experience much worse PMS than those who don't, according to researchers at the University of Massachusetts in Amherst. Your risk of developing PMS climbs the more you smoke and the younger you were when you first started puffing. Plus, those who smoke have shorter and more irregular menstrual cycles than non-smokers.

The good news: You can actually use your menstrual cycle to help you quit. Recent research shows that the decrease in estrogen from days 14 through 28 of your cycle (after ovulation and before your period arrives) can help keep withdrawal symptoms at bay so you can power through quitting.

11 of 13


Midsection of female healthcare worker explaining to young patient in medical clinic

Do you have long, unpredictable, or MIA periods? Polycystic ovary syndrome (PCOS) may be to blame. PCOS is the most common cause of infertility in people with vaginas because it is a hormonal imbalance where the body has high levels of androgens, which blocks ovulation. "When you don't ovulate, you don't get the release of progesterone, which causes you to get your period," says Dr. Minkin.

Here's the thing: Even if you had regular periods before, you may spontaneously develop PCOS for unknown reasons. In addition to being one of the causes of irregular periods, other signs of PCOS include acne, excessive hair growth, and weight gain. While birth control pills can help regulate your cycle, PCOS is associated with other serious health conditions such as obesity, diabetes, high blood pressure, heart disease, and more. Discuss your symptoms with your doctor if you think you might have PCOS.

12 of 13

High Amounts of Certain Hormones

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It's not the most-talked-about hormone, but prolactin plays a key role in the health of people with vaginas. The hormone causes breasts to grow during puberty, stimulates the production of breastmilk after childbirth, and helps control the menstrual cycle. But too much prolactin in the blood, a condition known as hyperprolactinemia, can be one of the causes of irregular periods. Other symptoms include vaginal dryness and production of breastmilk when you're not pregnant or nursing, according to the Endocrine Society.

Although growths or tumors in the pituitary gland of the brain (which makes prolactin) is the most common cause of the condition, some prescription medicines can also increase your levels of the hormone, including certain high blood pressure, depression, heartburn, nausea, and pain medications, per the Society. As always, talk to your doctor about any out-of-the-ordinary symptoms you're dealing with and the medications you're taking.

13 of 13

Uncontrolled Diabetes

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In addition to making your blood sugar levels go out of whack, uncontrolled type 1 and type 2 diabetes can cause irregular periods, according to the Office on Women's Health. What's more, uncontrolled diabetes in people with vaginas can delay the age that puberty begins and cause premature menopause, according to an article in the journal Women's Health. Luckily, better glycemic control and prevention of additional diabetes complications can improve period irregularities.

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