Why your periods change in your 40s

The big 4-0 might bring on a lot of changes—physically, mentally, emotionally—but a big one to look out for is the way your period changes in your 40s. Due to a phenomenon called perimenopause, most women will start noticing some changes in their cycle this decade. “Perimenopause is the four to maybe 10 years of hormonal volatility [before menopause] where your ovulation may be a little bit erratic and therefore, hormone levels—estrogen, progesterone, even testosterone—are variable,” explains Alyssa Dweck, MD, a gynecologist in Westchester County, New York.

Periods and perimenopause are inextricably linked: “One of the first symptoms people will notice is a change in their cycle,” says Dr. Dweck. And while these changes to your period are perfectly normal and to be expected, it helps to have an understanding and road map of what might be changing, exactly, and how it might change. Consider this your guide to the weirdness that is your period in your 40s.

How periods change in perimenopause

While changes to your period in your 40s are practically inevitable, there is no one way these changes typically happen. “The changes could be a skipped cycle (or two, or three or four); it could be an added cycle in the middle of your typical one-month cycle; it could be the amount of blood or the duration of blood that changes; or that the nature of the blood changes,” says Dr. Dweck. Most commonly, she says, her perimenopausal patients reach out because they’ve skipped a cycle or they’ve bled twice in one month. You also might notice increased or more uncomfortable cramping, says Dr. Dweck. Anything in this area—longer periods, shorter periods, heavier flows, lighter flows, and changes in cycle length— is par for the course during perimenopause.

Some environmental factors may contribute to the changes in your period and how perimenopause affects you, as well. “Smokers may have an earlier or worse experience with menopause,” says Dr. Dweck, meaning perimenopause will begin earlier as well. Research has also found that Black and Hispanic women have more hot flashes than women of Caucasian or Asian descent.

If someone in your immediate family—your mom, or an older sister—has been through menopause, this can be a great way to get some indication of what’s in store for you as far as changes to your period. “We do know that the age of onset is, in part, genetic, so you may get some insight from them,” says Dr. Dweck.

Lastly, while it’s super common to notice changes in your period in your 40s, it’s also normal not to, particularly if you’re on hormonal birth control. Medications like oral contraception or a long-acting reversible contraception like an IUD may “mask” the symptoms of perimenopause and make everything seem like business as usual. “Contraception equilibrates the hormone status throughout the month,” says Dr. Dweck. This is a good thing, so don’t stress if you’re on birth control and haven’t noticed any big changes.

While there’s no hard and fast cutoff for using hormonal birth control, Dr. Dweck says you can absolutely be on it during your perimenopausal years—they usually recommend people phase it out in their early 50s, so you’re doing the right thing by keeping your regimen if it’s working for you.

Is it perimenopause or something else?

If you’re noticing changes in your cycle and you’re over 40, the most likely cause is perimenopause, but that doesn’t mean it’s not worth seeing your doctor if things are beginning to shift. To determine what’s causing the differences in your period, your doc will look for other symptoms that indicate perimenopause, such as hot flashes, night sweats, change in sex drive, and mood changes and irritability. “Having no tolerance or patience may be a clue that hormonal changes are happening,” says Dr. Dweck.

While changes in your period are indicative of changes in ovulation as Dr. Dweck described, you can still get pregnant during perimenopause.  “If you are a person who is perimenopausal and you are having sexual relations [especially without birth control], you can get pregnant,” says Dr. Dweck. So one thing your doctor will want to do is rule out pregnancy, as it can cause irregular bleeding and (of course) missed cycles.

Sometimes perimenopause can cause other medical issues: If your period has gotten significantly heavier, it can trigger anemia in some women because of the extra blood loss. “This is something that definitely needs to be addressed because anemia can make people tired and fatigued,” says Dr. Dweck.

Occasionally, unusual periods will be caused by a thyroid imbalance. “An overactive or underactive thyroid can affect menstruation,” says Dr. Dweck. Medication can help improve these symptoms by synthetically producing the hormones your thyroid is meant to be responsible for, so this is another case where talking to your doctor is crucial.

In rare cases, irregular menstrual bleeding can be a sign of certain cancers—most typically, uterine cancer, though it could also be cervical or ovarian cancer. Only your doctor can evaluate if one of these cancers is causing your irregular periods, but if you’re concerned, make an appointment ASAP—they can do an ultrasound, biopsy and blood work to help rule this out.

Periods in your 40s: What you can do

First, don’t be afraid to contact your doctor. While changes to your cycle, mood and hormones are standard in your 40s, that doesn’t mean you have to suffer. “When those things become distressing to you or they start to interfere with your day-to-day life, that’s a time to check in with your provider,” says Dr. Dweck.

The easiest way to manage perimenopausal symptoms and erratic periods is hormonal therapy. “A natural suggestion for many people would be to use oral contraceptive pills, because not only do you get control of your cycle, but you also get the contraceptive benefit if it’s something that you need,” says Dr. Dweck. A hormonal intrauterine device (IUD) can be another great option, as they are known to be especially helpful with the heavy periods that can accompany perimenopause. You can always use over-the-counter pain medicines for increasingly painful cramps. Dr. Dweck also notes there are lots of options for mood changes, including low-dose antidepressants that can really help improve irritability.

More extreme symptoms may be treated with surgery, including dilation and curettage (D&C), which cleans the lining of the uterus “for both therapeutic and diagnostic purposes,” says Dr. Dweck, or a uterine ablation, “which is like a cauterization of the inside of the uterus to help control bleeding habits that are problematic during perimenopause.” In the most severe cases of bleeding, some people do get hysterectomies, says Dr. Dweck, but she notes those don’t help with the hormonal fluctuations that cause things like hot flashes. 

While the unknowns of perimenopause can be scary, the best thing you can do to prepare is to really try and get to know yourself, your body and your cycle. “Keeping a calendar or logging your cycle in an app is helpful because it gives you a picture of what’s going on repetitively and not something that’s just a one-off,” says Dr. Dweck. To the best that you can, keeping track of other changes to your routine—sleep, diet and exercise—can also give you insight into why you may be feeling crummy or out of sorts. In short, the more info you have, the better. “We may be a little bit better prepared for changes in the future because of this data we keep on ourselves.”

Featured expert

Alyssa Dweck, MD, is a board-certified gynecologist in Mount Kisco, New York, and the co-author of three books, including The Complete A to Z for Your V. She can be found at drdweck.com.


Dotlic J, Markovic N, Gazibara T. Patterns of smoking and menopause-specific quality of life: Smoking duration matters more. Behav Med. 2021; doi:10.1080/08964289.2021.1958739

Green R, Santoro N. Menopausal Symptoms and Ethnicity: The Study of Women’s Health across the Nation. Women’s Health. 2009; doi:10.2217/17455057.5.2.127