11 Sneaky Reasons Behind a Missed Period (Besides Pregnancy)

Updated: Feb. 10, 2021

An MIA Aunt Flo may feel like a blessing in disguise, but it's important to figure out why exactly your period has gone AWOL.

IUD birth control on a yellow table
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Your birth control method

Birth control pills, patches, rings, shots, and IUDs aren’t guaranteed to stop your cycle entirely, but a missed period is a recognized side effect of hormonal birth control—one many women are quite happy about. This is because hormonal birth control methods are designed to both inhibit ovulation and thin the lining of the uterus, explains Alyssa Dweck, MD, an ob-gyn in Mount Kisco, NY, and co-author of V is for Vagina: Your A to Z Guide to Periods, Piercings, Pleasures and So Much More. No egg to protect and no lining to shed means a lighter or non-existent period. The Mirena IUD and the Depo-Provera shot are the types most known for this side effect, along with pill packs, like Seasonique, that are designed for this express purpose.

Young woman running on a treadmill at gym while listening to music.
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You’re exercising too much

The “female athlete triad” refers to a pattern of undereating, amenorrhea (loss of periods), and osteoporosis that stem from an extreme workout routine. But despite the word “athlete” in the name, you don’t have to be bound for the Olympics to be at risk. It can affect women in any shape, form, or weight—not just the stereotypical “ballerina physique”—who are exercising too much. How much is too much? The answer is specific to each woman’s body and circumstances, but a good rule of thumb is if your workouts lead to a missed period, it’s too much for you.

Woman looking in the bathroom mirror, touching her face
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You have PCOS

Polycystic ovarian syndrome (PCOS) is an increasingly common cause of amenorrhea, says Renée Volny Darko, DO, a board-certified ob-gyn practicing in Duncansville, Pennsylvania. It can also cause weird periods, abnormal uterine bleeding, prolong periods and missed periods. PCOS is the most common hormonal endocrine disorder in women, affecting 5 to 10 percent of all women and is thought to be responsible for up to 70 percent of infertility. The syndrome is characterized by small, benign cysts  that grow on the ovaries (they represent non-ovulated eggs and show up on an ultrasound) and a rise in testosterone levels.  This extra testosterone prevents eggs from being released and can lead to symptoms like male-patterned baldness, acne, and excess facial hair. Other symptoms include insulin resistance, weight gain, and a lack of or irregular menstruation. As PCOS is linked with several serious health outcomes, it’s important to get this checked out if you have any of these PCOS symptoms.

Close up of woman's legs standing on a scale
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You lost weight too quickly

Weighing too much or too little are both known causes of amenorrhea, but losing weight very quickly can also lead to a missed period, even if your ending weight isn’t too low. Extreme weight loss is a shock to your metabolic system, which is closely tied to your reproductive system, according to the Mayo Clinic. Losing weight at a slower rate rather than trying to emulate the big results seen on some TV shows can fix this issue.

Woman sitting up in bed with her head leaning on her hand
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You’re sleep-deprived

Women who have irregular sleep may also have irregular periods. Researchers found that women who don’t get enough sleep or have poor-quality sleep end up with worse PMS and menstrual irregularities. Sleep plays a vital role in a woman’s health and well-being; when we skimp on sleep it’s not just under-eye bags we have to worry about—the rest of our systems suffer too. Don’t miss these other 13 mistakes that make your period more miserable.

Mature Woman Experiencing Hot Flush From Menopause
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You’re in perimenopause

Perimenopause, that strange no-(wo)man’s land between peak fertility and full-on menopause, starts earlier than you think, says Christine Northrup, MD, author of Women’s Bodies, Women’s Wisdom in Yarmouth, Maine. And a missed period is one of the most telltale signs you’re headed for The Change. Many women’s periods work like clockwork in their 20s, start to change in their 30s, and by their 40s are often quite irregular, she says. In addition to age, Dr. Northrup says you can recognize perimenopause symptoms as often like “PMS on steroids.”

stressed woman work computer

You’re under a crazy amount of stress

You may have written this one off as an old wives’ tale but it’s true. “Stress can definitely cause irregular or missing periods in a premenopausal woman,” Darko says, as being under a lot of pressure can mess with your hormone levels. Your body figures: If you’re this stressed out, then now is not the best time to have a baby, and temporarily shuts the fertility factory down, causing a missed period. These are other symptoms stress is making you sick.

Fresh Brussels sprouts in a bowl on a table.
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Your new diet is deficient

Many women find that when they drastically change their diet—say, by trying a ketogenic diet or a raw-foods vegan diet—they notice their periods become irregular or cease. If this is temporary it’s likely just your body adjusting but if it continues your diet might be the problem. One study found that clinical menstrual disturbances are more common in female vegetarians. While the authors cautioned against drawing any direct conclusions, they noted the association might be due to the lack of some nutrients that may be harder to get in certain diets, like iron. A separate study found that 45 percent of females on a low-carb diet experienced missing or irregular periods, often until they stopped the diet. But, like exercise, each woman’s body responds differently so what works for one woman may not work for you.

Woman blowing her nose into tissue

You’re fighting allergies

Birth control pills are the most obvious culprit when it comes to a missed period, but there are a host of other medications, both prescription and over-the-counter, that list period cessation as a possible side effect. Antidepressants, antipsychotics, chemotherapy drugs, allergy meds, and blood pressure pills are the top offenders, according to the Mayo Clinic. Learn more things every woman should know about her period.

Vitamins and supplements spilling out of a bottle onto a table
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You’re taking supplements

Just because it’s “natural” doesn’t mean it’s good for you. There are many herbs known to affect a woman’s hormones, fertility, and menstrual cycle, including raspberry leaf, black cohosh, forskolin, angelica root, sage, shepherd’s purse, and some types of ginseng. These herbs are all common ingredients in many popular supplement formulations for weight loss, PMS, menopause relief, breastfeeding, and other products targeted to women.

Sick man laying in bed under blanket and holding thermometer.

You have an underlying illness

Any condition that affects your ovaries, uterus, hypothalamus, or pituitary glands can mess up your monthly cycle. This can include illnesses like cancer, multiple sclerosis, hypothyroidism, and sexually transmitted diseases. It’s that last one you need to be particularly worried about, says David Diaz, MD, a reproductive endocrinologist and fertility expert at Orange Coast Memorial Medical Center in Fountain Valley, California. STDs like chlamydia, syphilis, and gonorrhea can fly under the radar, showing almost no symptoms at first while doing irreparable harm to your fertility. Don’t miss these other period problems you should never ignore.

Reader's Digest
Originally Published in Reader's Digest