11 Reasons Your Period Is Late When You Know You’re Not Pregnant

Believe it or not, the uterus or even the ovaries aren’t calling the shots to make your period happen each month, says Mary Jane Minkin, MD, clinical professor of obstetrics and gynecology at Yale University. “The control panel is in the brain,” she says. It’s the hypothalamus at the base of the brain that makes sure your reproductive hormones are in balance each cycle to do their respective jobs, so that you ovulate and menstruate every month, Dr. Minkin explains.

Any major deviation from the norm, including an influx of anxiety (say, from novel coronavirus-related issues like jobs on hold, sick relatives or friends, and being confined to your home), can mess with the delicate balance of hormones that regulate your cycle, and especially those that control ovulation. It might not be a coincidence that ovulation gets put on hold though, Dr. Minkin says. “From a philosophical point of view, maybe nature doesn’t want us to get pregnant if we’re really stressed.”

So…how much of a delay in your period is still considered normal?

“If you have one or two irregular periods it is definitely something to pay attention to,” says Sherry Ross, MD, an ob-gyn at Providence Saint John’s Health Center in Santa Monica, California. A period is considered late if it hasn’t started five or more days after the day you expected it to begin, according to Summit Medical Group. So if your period is, say, 10 days late, definitely take a pregnancy test and check in with your ob-gyn regardless of the results. In general, if your flow has been MIA for a week or more, that’s a sign you should take the test and also check in with your gyno to see what might be going on.

But again, you can miss a period and *not* be pregnant. If there’s no way you’re pregnant and/or your test comes back negative (though, you may be too early in your pregnancy to get a positive result just yet), one of these factors, including all the stress you might be under right now, may be to blame for your late period problems. Then, your next step is definitely calling your doc so they can help you suss out the best solution or treatment for your situation.

1. Stress

Significant stress—such as a divorce, death of a loved one, or, I don’t know, the effects of a global pandemic—can definitely disrupt your hormonal balance, creating delayed, irregular, and even heavy periods.

When all of that stress reaches the hypothalamus in the brain, which is supposed to be stimulating a series of hormone production, such as luteinizing hormone (which triggers ovulation), estrogen, and progesterone, that’s when things can go off the rails. The buildup of the stress hormone cortisol is also likely a factor in throwing off that balance, too, Dr. Minkin says. You need the estrogen and progesterone to prepare the uterus to receive a fertilized egg, but if those hormones aren’t in balance and you don’t end up actually ovulating, the whole system is off. Because of that lapse in timing, your period might not come on time either.

“You may skip periods altogether,” Dr. Minkin says, “or you may get a heavier period than usual.” The flow may be extra heavy because when you skip the ovulation stage, your body isn’t making the proper amount of progesterone, which regulates the thinning of the uterine lining, she says. If that doesn’t happen, your period is likely to shed more of the lining of the uterus, and therefore be heavier than normal.

2. Major weight loss

“We know excessive exercising, sudden weight changes and being underweight can offset your hormone levels,” says Dr. Ross. “One of these hormones is called leptin and is produced in fatty tissue. Excessive exercising and drastic weight changes can decrease the body fat causing this and other hormones (like estrogen) to drop, contributing to irregular periods.”

Talk to your doctor if you’ve had a major weight fluctuation recently so she can take that into account while solving your period probs.

3. Excessive exercise

Rigorous exercising, such as training for a marathon or triathlon, can cause physical stress, which may lead to a hormonal imbalance that screws with your period. Sound like you right now? Let your doctor know this information and what your workouts look like recently so she can help gauge whether they might be affecting your flow.

4. Polycystic ovary syndrome (PCOS)

PCOS is a medical condition caused by an imbalance of reproductive hormones, according to the Office on Women’s Health. It affects about 5 to 10 percent of women, says Dr. Ross.

“The hallmark of PCOS is irregular periods, excessive hair growth in places you would rather not see it, multiple cysts on the ovaries seen on a pelvic ultrasound, and infertility,” she says. “Your hormones—estrogen and testosterone—are completely lopsided and irregular.”

When you have PCOS, Dr. Ross says your periods can come every two weeks, every three to six months, or even just once a year. If you have any other symptoms of PCOS, take note and share them with your MD.

5. Your birth control

“One of the side effects of a low-estrogen birth control pill is a light or non-existent period,” Dr. Ross says. “For many, this is a welcomed side effect.” The same goes for methods like hormonal IUDs, implants, or shots, since many of those don’t contain estrogen at all.

But if you’ve just stopped taking the pill, then take note: Dr. Ross says it might take one to three months to return to your normal cycle. Still, pay attention to what your period looks like when it finally comes back. “It may be once you are off the pill you may find you have an underlying hormonal problem that was masked by taking the birth control pill,” says Dr. Ross.

If that’s the case for you, then it’s time to get in touch with your ob-gyn.

6. Thyroid dysfunction

The thyroid gland, located in your neck, regulates your metabolism, but it also interacts with many other systems in your body to keep things running smoothly. “If you’re dealing with any type of thyroid imbalance, whether it’s hypo- or hyperthyroidism, that can have implications for your period,” says Alyssa Dweck, MD, ob-gyn and co-author of V is for Vagina.

Dr. Ross says other hormonal causes that could lead to irregular periods include Cushing’s disease, poor control of diabetes mellitus, premature ovarian failure, and congenital adrenal hyperplasia (a condition that limits hormone production in the adrenal glands).

If you have any other symptoms, like fatigue or weight loss or gain, bring those up with your doctor, as they can help pinpoint whether a thyroid issue might be to blame. Then, your doctor will likely need to order blood tests and do a workup.

7. Miscarriage

If you took a pregnancy test and it showed you were pregnant, then your period (or something that looks like a period) arrived late and heavy, it could be a miscarriage, says Dr. Ross. Visit your doctor to discuss the bleeding and do an examination and ultrasound to confirm.

8. Certain medications

Whether you’ve been relying on certain OTC medications for an everyday headache or taking a prescription for a particular health issue, Dr. Ross says that some meds could be affecting your menstrual cycle. Aspirin, Coumadin (used to treat and prevent blood clots), and ibuprofen can all affect your cycle.

9. Pelvic inflammatory disease

This infection of the uterus, ovaries and/or fallopian tubes, which typically develops when chlamydia or gonorrhea is left untreated, can disrupt your cycle and cause irregular periods, according to Mayo Clinic.

10. Uterine fibroids

Uterine fibroids are noncancerous growths of the uterus, and they can cause heavy periods and super long periods, according to Mayo Clinic. This irregularity could make it seem like you’ve missed a period, too. If you have any other symptoms, like pelvic pain, frequent urination or even constipation, definitely bring those up with your doctor.

11. Premature menopause

When women under 40 have hormones misfiring in a significant way, they can go through premature menopause, also known as premature ovarian failure. Along with a missed period, signs of this condition include hot flashes, night sweats, and vaginal dryness.

But this shouldn’t be at the top of your list. “This isn’t very common, so you shouldn’t immediately worry about it,” says Dr. Dweck. If your ob-gyn rules out the many other potential causes for missed or late periods and thinks this may be the culprit, they’ll clue you in.

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