Irregular and Heavy Periods in Perimenopause

Menstrual regularity depends on a predictable hormonal sequence: estrogen rises in the first half of your cycle, you ovulate, and then progesterone rises in the second half to stabilize the uterine lining. When your period comes, it's because both hormones drop in an organized way, signaling the lining to shed evenly.

During perimenopause, this sequence becomes unreliable. As your ovarian reserve declines, you begin to have cycles where you don't ovulate (anovulatory cycles). Without ovulation, there's no progesterone rise in the second half of the cycle. Estrogen continues to stimulate the uterine lining, which keeps thickening without the organizing influence of progesterone. When it finally sheds — often later than expected — the result is typically heavier, more prolonged, and less predictable bleeding.

Even in cycles where ovulation does occur, the hormonal signals may be weaker or mistimed. FSH (follicle-stimulating hormone) rises as the brain tries harder to stimulate aging ovaries, which can cause estrogen levels to spike higher than normal before crashing. This hormonal volatility explains why perimenopausal periods can alternate between surprisingly heavy and unusually light — sometimes within consecutive months.

The pattern typically evolves over time. Early perimenopause often brings shorter cycles (every 24-26 days instead of 28), while later perimenopause brings longer gaps between periods, with heavier flow when they do arrive.

It's important to distinguish between "heavier than your normal" — which is common and expected during perimenopause — and genuinely abnormal heavy menstrual bleeding (HMB) that warrants medical evaluation. The clinical definition of HMB is blood loss greater than 80 mL per cycle, but since no one measures their menstrual blood, practical indicators are more useful.

You should consider your bleeding abnormally heavy if you're soaking through a regular pad or tampon every 1-2 hours for several consecutive hours, passing blood clots larger than a quarter (about 2.5 cm), needing to double up on protection (pad plus tampon), experiencing periods lasting longer than 7 days, needing to set an alarm to change protection overnight, or if bleeding is interfering with your daily activities.

The reason heavy perimenopausal bleeding needs evaluation isn't just comfort — it's medical. Chronic heavy bleeding can cause iron-deficiency anemia, which manifests as fatigue, brain fog, dizziness, hair loss, and shortness of breath. Many women attribute these symptoms to perimenopause itself and don't realize they're anemic. A simple blood count (CBC) and ferritin level can identify this.

Additionally, heavy or irregular bleeding during perimenopause can sometimes indicate structural causes that need treatment — such as uterine fibroids, endometrial polyps, or in rare cases, endometrial hyperplasia or cancer. Evaluation typically includes a pelvic ultrasound and may include an endometrial biopsy, especially for women over 45 with persistent abnormal bleeding.

"Flooding" — the sudden, heavy gush of blood that can soak through clothing with little warning — is one of the most distressing perimenopausal period symptoms. It happens because of the anovulatory cycle dynamic: without progesterone to organize and stabilize the uterine lining, the endometrium builds up unevenly. When parts of this thick, disorganized lining finally break down, it sheds in large, irregular sections rather than in the controlled, gradual way of a normal period.

Blood clots during heavy perimenopausal periods are formed by the same mechanism. Your body produces anticoagulants to keep menstrual blood liquid, but when flow is very heavy, the blood exits faster than anticoagulants can work. The result is clots — which are essentially pieces of organized blood and endometrial tissue. Small clots (smaller than a dime) are generally not concerning, but larger or frequent clots suggest the bleeding is heavy enough to warrant evaluation.

The unpredictability of flooding is what makes it particularly stressful. Many women in perimenopause describe anxiety about being caught off guard — at work, on a long drive, in a meeting. Practical strategies include wearing period underwear as a backup layer, keeping a change of clothes available, using menstrual cups or discs (which hold more than pads or tampons), and tracking your cycle to anticipate when heavier episodes are likely.

If flooding is frequent or severe, medical treatment options include hormonal approaches (the Mirena IUD, which dramatically reduces menstrual bleeding, or cyclic progesterone) and non-hormonal options like tranexamic acid, which reduces blood loss by stabilizing clots.

The levonorgestrel intrauterine device (LNG-IUD), commonly known by the brand name Mirena, is one of the most effective treatments for heavy perimenopausal periods. It releases a small amount of progestin directly into the uterus, which thins the endometrial lining and dramatically reduces menstrual bleeding — most women see a 90% or greater reduction in blood loss within 3-6 months, and some stop bleeding altogether.

For perimenopausal women, the Mirena offers several advantages beyond period management. It provides reliable contraception (pregnancy is still possible during perimenopause until you've reached menopause), it protects the endometrium from the effects of unopposed estrogen (reducing the risk of endometrial hyperplasia), and if you later decide to use estrogen therapy for other perimenopausal symptoms, the Mirena can serve as the progestogen component of hormone therapy.

The LNG-IUD lasts up to 8 years for contraception and is generally well-tolerated. Side effects can include irregular spotting in the first 3-6 months, and some women report mood changes or breast tenderness, though systemic absorption is much lower than with oral progestins. For most perimenopausal women, the benefits of lighter periods, endometrial protection, and contraception make it a highly practical choice.

It's worth noting that the Mirena does not treat other perimenopausal symptoms like hot flashes, sleep disruption, or brain fog — those are driven by systemic hormonal changes that a local intrauterine device doesn't address. For comprehensive symptom management, the Mirena is often combined with systemic estrogen therapy.

Intermenstrual bleeding — spotting or bleeding between your regular periods — is common during perimenopause but should always be mentioned to your healthcare provider, particularly if it's new, persistent, or occurs after sex. While it's often caused by the same hormonal fluctuations that make periods irregular, it can also indicate conditions that need evaluation.

The most common benign causes of intermenstrual bleeding during perimenopause include breakthrough bleeding from hormonal fluctuations, cervical polyps (small, usually harmless growths on the cervix), and endometrial polyps. These are all treatable and not dangerous, but they need to be identified.

More concerning causes include endometrial hyperplasia — a thickening of the uterine lining that can result from prolonged exposure to estrogen without sufficient progesterone. Simple hyperplasia is common and treatable, but atypical hyperplasia requires closer monitoring or treatment because it can be a precursor to endometrial cancer. Endometrial cancer itself is relatively rare in perimenopausal women but is the reason that abnormal bleeding in women over 45 is taken seriously.

Your doctor will likely perform a pelvic exam, transvaginal ultrasound (to measure endometrial thickness and identify polyps or fibroids), and possibly an endometrial biopsy. The biopsy involves taking a small sample of the uterine lining — it's done in the office, takes a few minutes, and while uncomfortable, provides critical information about the health of your endometrium. If you're offered this evaluation, don't delay — early detection of any abnormality leads to better outcomes.

Tracking your cycle during perimenopause serves a different purpose than tracking during your reproductive years. You're no longer trying to predict a regular pattern — instead, you're building a record that helps you and your healthcare provider understand your hormonal transition and identify anything that needs evaluation.

Record the first day of each period, its duration, and an estimate of flow (light, moderate, heavy, flooding). Note any spotting between periods, clots, and whether you needed to change protection more frequently than usual. Many period-tracking apps allow you to log these details, though be aware that their prediction algorithms may become unreliable as your cycles grow irregular — don't rely on them for contraception during perimenopause.

Beyond bleeding patterns, tracking symptoms alongside your cycle provides valuable information. Note sleep quality, mood changes, hot flashes, headaches, breast tenderness, and energy levels. Over several months, you may begin to see patterns — for example, that your worst insomnia and anxiety occur in the week before a period, suggesting a progesterone-related pattern, or that hot flashes cluster around ovulation.

Bring this record to your medical appointments. A 3-6 month symptom diary is often more diagnostically useful than a single blood test. It helps your provider distinguish normal perimenopausal variation from patterns that suggest fibroids, polyps, thyroid dysfunction, or other treatable conditions. It also provides a baseline against which to measure the effectiveness of any treatment you start.