Cycles that shift in your 40s are usually the menopause transition at work. But "probably perimenopause" is a conclusion to reach after an evaluation, not instead of one. Here is what tends to change, what shouldn't be waved off, and what a gynecologist actually does to find out.
Heavier or less predictable periods are common during perimenopause because ovulation becomes less regular. But new or persistent abnormal bleeding should not automatically be attributed to perimenopause. Fibroids, polyps and other conditions can cause similar changes, so your age, bleeding pattern, medical history and other risk factors determine whether testing such as ultrasound or endometrial sampling is appropriate.
In a regular cycle, ovulation triggers progesterone, and progesterone is what keeps the uterine lining organized and brings on a period at a predictable time. In perimenopause, ovulation becomes hit or miss. In months when an egg isn't released, the lining keeps building under the influence of estrogen without progesterone to stop it, then sheds late, unevenly, and often heavily. ACOG describes exactly this pattern: lack of ovulation "can cause irregular, sometimes heavy, menstrual bleeding," and when ovulation is skipped for several cycles, areas of the lining can become too thick.
The practical result is a period that no longer behaves. Early in the transition, cycles often get a little shorter and flow may be heavier or lighter than it used to be. As the transition progresses, The Menopause Society notes that cycle length may vary by seven days or more, and later on women may skip 60 days or longer between periods. Along the way, a single very heavy period, a skipped month followed by a long one, and a few cycles of spotting are all common. Tracking bleeding on a calendar or an app turns that chaos into information a clinician can actually read.
Sources: ACOG, Abnormal Uterine Bleeding · The Menopause Society, Perimenopause
Variation is expected in the transition. Certain patterns are not, and they are the same patterns ACOG and the National Institute on Aging flag at any age. Be evaluated for bleeding that soaks through a pad or tampon every hour or two, periods that last more than seven days, cycles arriving closer than every three weeks, bleeding or spotting between periods or after sex, and periods that have stopped for three to six months without explanation. Symptoms of iron deficiency, such as fatigue that rest doesn't fix, dizziness, or shortness of breath with ordinary activity, count as a reason too, because heavy bleeding can quietly cause anemia.
Two rules have no exceptions. Any bleeding after 12 consecutive months without a period is postmenopausal bleeding and needs prompt evaluation, no matter how light; our guide to bleeding after menopause explains why. And bleeding at the pace of a pad or tampon an hour for more than two hours in a row, with chest pain, shortness of breath, or lightheadedness, is an emergency. Everything short of those is a reason to schedule, not to panic, but it is a reason to schedule. The Menopause Society puts it plainly: "Don't assume that any abnormal bleeding is simply part of normal menopause."
Sources: National Institute on Aging, What Is Menopause? · ACOG, Abnormal Uterine Bleeding · The Menopause Society, Symptoms
Perimenopause is the most common explanation for bleeding changes after 40, and it is also the easiest to hide behind. Uterine fibroids and endometrial polyps, both usually noncancerous, peak in exactly these years and cause heavy or irregular bleeding of their own. Adenomyosis, where lining tissue grows into the muscle of the uterus, classically produces heavy, painful periods in the 40s. Thyroid disease disrupts cycles at any age. Blood thinners and some other medications increase flow.
The reason gynecologists are careful here is the uterine lining itself. Years of estrogen without regular progesterone, the very mechanism behind perimenopausal bleeding, can lead to endometrial hyperplasia, a thickening of the lining that is sometimes precancerous. ACOG notes that abnormal uterine bleeding "can be an early sign of endometrial cancer." Most endometrial cancer occurs after menopause and most abnormal bleeding in the 40s is benign, but the group of women whose bleeding deserves a closer look is precisely this one, which is why age 45 shows up as a line in the guidance below.
Source: ACOG, Abnormal Uterine Bleeding
The workup starts with the story and a pelvic exam: how your bleeding has changed, your contraception, your medications, and your family history. A pregnancy test is checked when it applies, because pregnancy remains possible in perimenopause, and a complete blood count looks for anemia. Thyroid testing is added when the history suggests it. A transvaginal ultrasound is the usual next step for new heavy or irregular bleeding in your 40s. ACOG guidance calls for evaluating the uterus "at least with a screening transvaginal ultrasonography" when a structural cause is possible, and the scan shows fibroids, polyps, the thickness of the lining, and the ovaries in a few minutes without radiation or anesthesia.
The second question is whether the lining itself needs to be sampled. ACOG's guidance is specific: endometrial tissue sampling should be performed as a first-line test in women with abnormal uterine bleeding who are older than 45, and in younger women who have had long stretches of estrogen without progesterone (such as with obesity or PMOS, also known as PCOS), whose bleeding persists, or whose medical treatment hasn't worked. An endometrial biopsy is a brief office procedure in which a thin, flexible tube is passed through the cervix to collect a small sample of the lining. It causes cramping for a minute or two and gives a direct look at the tissue. When the ultrasound suggests a polyp or fibroid inside the cavity, saline-infusion sonography (ultrasound with a little fluid in the uterus) or hysteroscopy (a thin scope passed into the uterus) shows it clearly and can guide removal.
So, do you need an ultrasound for heavy bleeding? Not every woman with one heavy period does. But if bleeding is new, heavy, persistent, or between periods, or if the exam suggests an enlarged uterus, imaging is usually part of the answer, and at 45 or older the lining is usually sampled alongside it. At Sparrow Women's Health in Winter Garden, Florida, pelvic and transvaginal ultrasound are performed in the office by Dr. Megan Luciano, a board-certified gynecologist, at the same visit when they are needed, and endometrial biopsy is performed in the office as well.
Sources: ACOG Committee Opinion No. 557 · ACOG Practice Bulletin No. 128
When the evaluation shows a lining that is healthy and ovulation that is simply erratic, treatment aims at the bleeding itself, and ACOG notes that medications are usually tried first. The hormonal IUD is one of the most effective options for heavy bleeding, often reducing periods to light spotting or nothing, and it also provides the contraception that perimenopause still requires. Combined birth control pills, the patch, or the ring regulate cycles and lighten flow for women who can safely use estrogen. Progestin-only options, including cyclic oral progestin, thin the lining directly. Tranexamic acid, a nonhormonal tablet taken only during the period, and anti-inflammatory medications such as ibuprofen reduce flow without affecting hormones.
Hormone therapy itself can be part of the plan: ACOG notes it "can be helpful for heavy menstrual bleeding that occurs during perimenopause" while also treating hot flashes and night sweats, a choice our guide to hormone therapy during perimenopause covers in detail. Iron is replaced when bleeding has caused anemia. When a polyp or fibroid is the cause, removing it treats the problem at its source, and procedures such as endometrial ablation or hysterectomy are reserved for bleeding that medication cannot control in women who have finished childbearing. Because all of these choices depend on what was found, the evaluation isn't a formality; it is what makes the treatment fit.
Source: ACOG, Abnormal Uterine Bleeding
Age is the first variable, with 45 as the line where lining sampling becomes routine for abnormal bleeding. Weight, a history of PMOS (PCOS) or long stretches of irregular cycles, and diabetes all raise the likelihood of lining overgrowth and lower the threshold for a biopsy at younger ages. A family history of endometrial or colon cancer, especially Lynch syndrome, does the same. Blood thinners, a known bleeding disorder, or periods that have been heavy since adolescence point the workup in a different direction. And whether you want to avoid pregnancy, are open to an IUD, or can safely take estrogen shapes which treatments are even on the table. None of this makes the answer complicated; it makes it yours.
Source: ACOG Committee Opinion No. 557
Any of these in your 40s is a reason to be evaluated rather than to wait for menopause to sort it out.
The goal is a real answer about what is causing the bleeding, and a plan that treats that cause rather than a guess.
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