A normal period lasts between 2 and 7 days. If yours is stretching beyond that window, or if it’s noticeably longer than what’s typical for you, something has shifted in your body’s usual rhythm. The causes range from simple hormonal fluctuations to underlying conditions worth investigating, and most of them are treatable once identified.
How Hormonal Imbalance Extends Bleeding
The most common reason for a longer-than-usual period is a disruption in the balance between your two main reproductive hormones: estrogen and progesterone. Together, these hormones control how thick the uterine lining grows each month and when it sheds. When the balance tips, the lining can build up more than it should, and shedding that extra tissue takes longer and produces heavier flow.
One specific way this happens is when your body skips ovulation during a cycle. Normally, releasing an egg triggers a surge of progesterone, which is the hormone most responsible for keeping periods regular and predictable. If no egg is released, progesterone stays low, and the lining keeps thickening under estrogen’s influence. When it finally sheds, the result is prolonged or unexpectedly heavy bleeding. You may not even realize you skipped ovulation, since bleeding still occurs. It’s just driven by a different mechanism than a true period.
PCOS and Skipped Ovulation
Polycystic ovary syndrome is the single biggest driver of skipped ovulation, responsible for roughly 70% of anovulation cases. PCOS causes your body to produce excess androgens (sometimes called “male hormones,” though everyone has them). These elevated androgens prevent the follicles in your ovaries from maturing properly, so an egg is never released. Without ovulation, progesterone stays low, the uterine lining builds up unchecked, and when bleeding eventually comes it can last well beyond a week.
Other signs that PCOS might be involved include irregular or unpredictable cycles, acne, thinning hair on your head, or excess hair growth on the face and body. If several of those sound familiar alongside your longer periods, it’s worth bringing up with a healthcare provider.
Thyroid Problems
Your thyroid gland helps regulate your menstrual cycle, so when it’s producing too much or too little hormone, your periods feel the impact. An underactive thyroid (hypothyroidism) is linked to heavier, longer menstrual bleeding. An overactive thyroid tends to do the opposite, making periods lighter and less frequent. Thyroid disorders are common in women and often go undiagnosed for years because symptoms like fatigue, weight changes, and mood shifts are easy to attribute to other things. A simple blood test can check thyroid function.
Fibroids and Polyps
Structural growths inside or on the uterus are another frequent culprit. Uterine fibroids are noncancerous muscle tissue growths, while polyps are overgrowths of the uterine lining itself. Both can physically increase the surface area that bleeds during a period, making it last longer and flow heavier.
Polyps are estrogen-sensitive, meaning they grow in response to estrogen levels in your body, and they’re especially common during or after perimenopause. Fibroids can range from tiny to quite large. Either type can cause periods that feel unpredictable in length and heaviness, along with spotting between cycles. An ultrasound is typically the first step to identify them.
Perimenopause
If you’re in your late 30s or 40s, the hormonal shifts of perimenopause could easily explain a change in your period length. During this transition, your ovaries gradually produce less estrogen, which throws off the balance with progesterone. Ovulation becomes less reliable, sometimes happening and sometimes not, which makes cycles erratic. You might have a short, light period one month and a long, heavy one the next. Some cycles stretch out to 40 or 50 days between periods; others arrive early. This phase can last several years before menopause.
Your IUD or Medications
A copper IUD is well known for making periods heavier and longer, especially in the first three to six months after insertion. Because the copper IUD doesn’t use hormones, it doesn’t suppress your natural cycle, but the device itself can cause the uterus to produce more inflammation, leading to extended bleeding and stronger cramps. These side effects typically ease over time, but for some people they persist.
Blood-thinning medications are another documented cause. Abnormal uterine bleeding is a recognized side effect of anticoagulant drugs, and the incidence varies depending on which type you’re taking. If you started a blood thinner and noticed your periods getting longer or heavier, that connection is real and worth discussing with whoever prescribed it.
When Longer Periods Signal Something Serious
A period that runs a day or two longer than usual once in a while is rarely cause for alarm. Stress, travel, illness, or a single skipped ovulation can all throw off a single cycle. But certain patterns and symptoms call for prompt attention:
- Soaking through pads or tampons fast: Bleeding through two or more pads or tampons per hour for two to three consecutive hours is a sign you need medical care right away.
- Large blood clots: Passing clots the size of a quarter or bigger more than once or twice during a period is considered abnormal.
- Periods consistently over 7 days: Clinically, monthly bleeding that exceeds 7 days or totals more than 80 milliliters (roughly 5 to 6 tablespoons) meets the definition of heavy menstrual bleeding, or menorrhagia.
- Fatigue and dizziness: These can signal iron-deficiency anemia from ongoing blood loss, which is one of the most common complications of prolonged periods.
How Longer Periods Are Evaluated
If your periods have been consistently longer or heavier than normal, a provider will typically start with blood work to check for anemia, thyroid dysfunction, and clotting disorders. From there, the investigation depends on what those results suggest.
An ultrasound can reveal fibroids, polyps, or other structural changes in the uterus. A more detailed version called sonohysterography involves injecting a small amount of fluid into the uterus during the ultrasound to get a clearer picture of the lining. If there’s concern about abnormal cells, an endometrial biopsy takes a small tissue sample from inside the uterus to check for precancerous or cancerous changes. A hysteroscopy, where a thin camera is inserted through the cervix, lets a doctor look directly at the uterine lining.
None of these tests are routine for a single longer-than-usual period. They become relevant when the pattern repeats, when bleeding is very heavy, or when other symptoms point toward a specific cause. The goal is to identify what’s driving the change so treatment can target the actual problem rather than just managing the bleeding.