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Maybe your monthly visitor reminds you of that friend who always shows up late to drinks — and sometimes not at all. Periods do occasionally flake.

First of all, don’t freak out. Irregularities in menstrual cycles aren’t all that rare. Lots of people miss a period every once in a while. Studies show that 5 to 35 percent of menstruating women have irregular periods.Kwak Y, et al. (2019). Prevalence of irregular menstruation according to socioeconomic status: A population-based nationwide cross-sectional study. DOI: 10.1371/journal.pone.0214071

When you have a menstrual cycle that extends to 6 weeks or more but is less than 6 months, it’s called oligomenorrhea. If your period disappears for 6 months or longer, that’s called secondary amenorrhea.

And while your initial — and very valid — thought about skipping a cycle or two might be that you’re pregnant, a number of lifestyle and health factors can also prompt your menses to take a mini-vacay.

Still, if you’re sexually active, never wait to take an OTC pregnancy test or visit your doc for a blood or urine test to rule out a potential bun in the oven. And if you’ve skipped three or more periods and you’re sure you aren’t pregnant, pay a visit to your OB-GYN, primary care physician, or an endocrinologist.

In the meantime, here are nine common reasons your period could be AWOL — and what you can do to get things back on track.

Chronic stress takes a serious bite out of our well-being, and it’s one of the primary causes of secondary amenorrhea.Meczekalski B, et al. (2014). Functional hypothalamic amenorrhea and its influence on women’s health. DOI: 10.1007/s40618-014-0169-3

Too many stress hormones coursing through your bloodstream can signal your brain to slow down or temporarily halt reproductive function until your environment or situation improves.

One study looked at female students in Saudi Arabia. Among the students surveyed, 27 percent had irregular menstruation. The researchers found a link between fluctuation in cycles and the students’ perceived level of stress.Rafique N. (2018). Prevalence of menstrual problems and their association with psychological stress in young female students studying health sciences. DOI: 10.15537/smj.2018.1.21438

So whether you’re having a tough time during finals, struggling with work-related stressors, going through a breakup, or dealing with a major trauma like abuse, your body may react by sending your period on hiatus.

What to do:

If you’re facing everyday stressors, take a look at how you can alleviate them. Try meditation and other ways to relax. You’ll likely be once again surfing the crimson wave next month.

BTW, if you’re experiencing domestic violence seek help immediately. Find resources for assistance and make a game plan for getting out of the relationship. If you’ve been sexually assaulted, these resources for survivors can help.

What you eat can play a big role in keeping your cycle on an even keel. A review of existing scientific studies suggests a link between nutritional deficiencies and menstrual cycle irregularities, and also a delayed start to menstruation.Jahangir A. (2018). Do nutritional deficiencies lead to menstrual irregularities? http://biocoreopen.org/articles/Do-nutritional-deficiencies-lead-to-menstrual-irregularities.pdf

Not noshing a balanced diet deprives the body of key macronutrients — think protein, fat, and carbs. Plus, certain micronutrients, aka vitamins and minerals, are required to make sex hormones. Those include calcium, magnesium, iron, and zinc.

Having nutritional deficiencies and not eating enough calories can stress your body and send your period packing.

Meal times are important as well. A 2014 study of 300 females ages 17 to 22 found a link between those who skipped breakfast and those who had irregular menstrual cycles.Eittah HF, (2014). Effect of breakfast skipping on young females’ menstruation. http://www.hsj.gr/medicine/effect-of-breakfast-skipping-on-young-females-menstruation.pdf

What to do:

If you suspect your diet is the culprit for your departed red sea, talk to your health care provider. Your doctor can test you for nutritional deficiencies and help you find a solution to get your body back on track.

Keep in mind that conditions that affect the gut, like celiac disease, can cause nutrient malabsorption and may be to blame for a period that’s playing hooky. Talk to your doctor before going gluten-free, however.

Exercise is good for you, but it burns energy. And if you don’t properly refuel to keep up with the demands you place on your body, it may react by turning off reproductive processes.

Although amenorrhea is reported in 37 percent of female athletes, you don’t have to train like a gold medalist for your period to take a hike.

A small study of untrained women linked menstruation disturbances to a daily energy deficit of 500 to 800 calories created with diet and exercise over the course of three menstrual cycles. Issue frequency was greatest in those who had the largest energy deficits.Williams NL, et al. ( 2015). Magnitude of daily energy deficit predicts frequency but not severity of menstrual disturbances associated with exercise and caloric restriction. DOI: 10.1152/ajpendo.00386.2013

Even if we’re able to eat enough to offset unnecessary weight loss, research shows exercise lowers the amount of female sex hormones — namely estrogen and progesterone — swimming around in our systems.Ennour-Idrissi K, et al. (2015). Effect of physical activity on sex hormones in women: a systematic review and meta-analysis of randomized controlled trials. DOI: 10.1186/s13058-015-0647-3

When we go overboard on exercise, and these hormones dip too low, we dampen part of the chemical communication chain that normally gives rise to predictable periods.

What to do:

If you’re wondering if you’re experiencing too big of an energy deficit, talk to your doctor or enlist the help of a registered dietitian specializing in fitness nutrition.

You can also take a look at your exercise regimen. Do you need to dial back your running, cycling mileage, or your days at the gym?

This isn’t a side effect to ignore, says Nichole Tyson, M.D., an OB-GYN at Kaiser Permanente and member of the American College of Obstetricians and Gynecologists.

Some women with amenorrhea related to eating disorders or excessive exercise can also be predisposed to heart disease, osteopenia, and osteoporosis later in life, she says.

Having a low weight can make Aunt Flo stop in her tracks.

Less fat means lower levels of leptin — a hormone produced by fat cells that plays a huge role in triggering ovulation and menstruation, says Sherry Ross, M.D., an OB-GYN and women’s health expert at Providence Saint John’s Health Center in Santa Monica.

Too much body fat might also disrupt the menstrual cycle because having overweight may cause leptin resistance.Chou SH, et al. (2014). 20 years of leptin: Role of leptin in human reproductive disorders. DOI: 10.1530/JOE-14-0245

What to do:

Get an evaluation from your physician. There’s no specific weight above or below which you’re guaranteed to stop ovulating or menstruating or a specific weight that will dictate the return of your cycle, Tyson says.

“Everyone has their own set point,” she explains. So don’t stop seeking answers for why your cycle’s out of whack simply because you’re a few pounds heavier or lighter than your friends.

Having an under- or overactive thyroid can also give rise to unreliable menses, says Dena Harris, M.D., OB-GYN, and founder of Maiden Lane Medical in New York City.

According to the American Thyroid Association, approximately 20 million Americans have some kind of thyroid disease — with women being five to eight times more likely than men to be diagnosed.

Hyperthyroidism is characterized by heart palpitations, weight loss, intolerance of heat, and increases in appetite, sweating, and bowel movements.

Hypothyroidism symptoms include weight gain, lethargy, depressed mood, facial puffiness, constipation, and a slower heart rate.

A condition called polycystic ovary syndrome (PCOS) may also be a cause for missed or irregular periods, Tyson says. PCOS affects one in 10 women, according to the Office on Women’s Health.

In PCOS, there are imbalances in estrogen, progesterone, and androgen — a male hormone women usually produce in far smaller amounts — which can lead to irregular or infrequent ovulation.

Symptoms vary but can include acne, thinning hair, increased face and body hair, obesity, and type 2 diabetes, explains Jaime Arruda, M.D., an OB-GYN.

Finally, premature ovarian failure (POF) — aka early menopause — may also explain why a younger woman’s periods may be absent for many months.

What to do:

If any of these above signs ring a bell, see your doc ASAP. “Women with PCOS can have long-term risks of serious health conditions, such as heart disease and diabetes,” Tyson says.

Some over-the-counter (OTC) pain relievers — like aspirin, ibuprofen, and naproxen — have been found to screw with menstrual cycles, Ross says. As can some thyroid medications, since they alter the levels of hormones that interact with initiating ovulation and menstruation.

Certain antidepressants like Prozac and Zoloft can increase our body’s levels of prolactin — a hormone that normally promotes lactation following pregnancy but also shuts down our menstrual cycle, Harris adds.

Opioids (prescription pain relievers), blood pressure medications, and antipsychotics can also affect menstrual cycles, according to Arruda.

What to do:

Ask your physician if any of the medications you’re taking could have kidnapped your period.

Most birth control pills and patches prevent pregnancy by halting ovulation. Sometimes this results in a few periods jumping ship as well. This is totally normal in many cases, Ross says.

IUDs, on the other hand, do not halt ovulation. Ross notes: “You still ovulate, but IUDs create an inflammatory reaction in the uterus that prevents sperm from accessing the fallopian tube, where fertilization would take place.” Curious? Here’s how to decide if an IUD is right for you.

What to do:

If you go off the pill and don’t resume a red alert within 3 months, something else may be going on in your body. Ross says the pill can mask underlying issues that only surface once you stop taking it. It’s important to talk to your doctor.

Likewise, see your health care provider if you’ve always had regular periods on the pill, but they’ve suddenly gone on hiatus.

If you’re a smoker, you may be more prone to skipped periods. In one study, researchers found smoking to be a risk factor for menstrual irregularity.Bae J, et al. (2018). Factors associated with menstrual cycle irregularity and menopause. DOI: 10.1186/s12905-018-0528-x

What to do:

Talk to your doctor about finding a way to quit that’s right for you.

A bout of the flu or other illness could throw off your cycle and result in a missed period. Although, scientific research is lacking on the exact reason, we can theorize that it’s the resulting physical and mental stressors that can make your period go bye-bye.

And illnesses can pack that double whammy. Not only does the flu make you miserable, you may also be stressed about missing school or work or worried about your health in general.

What to do:

See a doctor for an illness when necessary, and focus your energy on getting well. That means rest up and get plenty of fluids.

If you’ve missed more than one period, you’re sure you’re not pregnant, and you’ve exhausted all possibilities, make an appointment with your OB-GYN to figure out the mystery.

However, it’s important to remember that an occasional missed red badge of courage can be completely normal and not cause for concern. If you’ve only skipped one, it’s possible, and even likely, that your period ghosted for no reason at all.