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    Periods during perimenopause: What to expect

    Updated 07 December 2023 |
    Published 27 August 2019
    Fact Checked
    Dr. Ruth Olumba
    Medically reviewed by Dr. Ruth Olumba, Obstetrician, gynecologist, and gynecologic and cosmetic surgeon, Texas, US
    Written by Abi Millar
    Flo Fact-Checking Standards

    Every piece of content at Flo Health adheres to the highest editorial standards for language, style, and medical accuracy. To learn what we do to deliver the best health and lifestyle insights to you, check out our content review principles.

    You might notice your periods changing during perimenopause. Knowledge is power, so here’s everything you need to know.

    Do you remember getting “the puberty talk” in health class? When your first period arrived, you hopefully knew roughly what to expect. But the same isn’t always true for perimenopause, the transitional phase before menopause (which you officially reach when you haven’t had a period for 12 months). 

    Perimenopause generally begins in your 40s but can start as early as your mid-30s. And one of the first signs you might notice is new changes to your period.

    If your period has arrived like clockwork all your life — only to start behaving more like a temperamental house guest — you may wonder what’s happening. “If we give young girls puberty talks, we should be giving women peri talks,” says obstetrician and gynecologist Dr. Sameena Rahman from Illinois, United States. She likes to give her patients a heads-up about perimenopause before they get there. 

    Side note: If you don’t have periods because, for instance, you take hormonal contraception continuously or have had your uterus surgically removed, you’ll still go through menopause transition.

    Think you might be perimenopausal?

    Tracking your symptoms can help you and your doctor work out what's going on

    Why do period changes happen in perimenopause?

    During perimenopause, your ovaries start producing estrogen erratically, meaning levels can surge very high before dropping dramatically. Progesterone, another hormone produced by your ovaries, gets thrown off-kilter, too. Once you reach menopause, the roller coaster stops, and estrogen levels stay low.

    Period changes don’t necessarily mean you’re in perimenopause. And some people have regular periods through to menopause. But if you’re in your late 30s or 40s, and especially if you’re experiencing other symptoms (such as hot flashes and mood changes), perimenopause is something to consider.

    What are periods like during perimenopause?

    Let’s look at some of those possible period changes you might experience. 

    Irregular periods

    Whether you’ve had a regular cycle all your life or your periods have always been variable, you probably have a baseline of what’s normal for you — especially if you’re regularly tracking them in Flo. Perimenopause can make your periods harder to predict. 

    In medical terms, “irregular periods” doesn’t just mean they’re out by a day or two. Instead, it’s when the length between cycles (the time between one period starting and the next) consistently varies by more than seven days. For instance, one cycle is 29 days, the next is 40 days, the next is 25, and so on.

    One Secret Chats community member described their cycle as “intermittently irregular.” “By that, I mean I will have my usual 26- to 28-day cycle for a few months, and then it will be 38 days. It really freaked me out the first time,” they said. 

    Longer or shorter cycles

    During perimenopause, you might also find that your cycle is longer or shorter than you’re used to.

    Two big studies (albeit from the 1960s) found that women in their 40s had an average cycle length of 26 days compared to 29 days for women in their 20s. This isn’t a huge change, but it’s big enough that you’d notice. But know this — if you’re not in your 40s and your cycle lasts an average of 26 days, that’s totally fine and not necessarily a sign of perimenopause. 

    Dr. Rahman says that in early perimenopause, it’s common to find that periods get closer together. “In later perimenopause, you may find that you have cycles that are spaced out, maybe 60 days apart or longer,” she adds.