A normal period lasts between 3 and 7 days. If yours regularly stretches past 7 or 8 days, something is causing your uterine lining to shed longer than it should. The reasons range from simple hormonal shifts to underlying conditions worth investigating, and most of them are treatable once identified.
What Counts as “Too Long”
Most adult menstrual cycles fall between 21 and 34 days from start to start, with the actual bleeding portion lasting up to 7 days. A period is considered prolonged once it exceeds 7 to 8 days. Heavy menstrual bleeding, sometimes called menorrhagia, is defined as losing more than 80 mL of blood per cycle, roughly equivalent to soaking through a pad or tampon every two hours or less.
If you’re a teenager, longer and more irregular cycles are common in the first few years after your period starts. About 90% of cycles during that time fall between 21 and 45 days, and it can take three years for cycles to settle into a more predictable adult pattern. A long period at 14 is much less concerning than one at 30.
You May Not Be Ovulating
One of the most common reasons for a period that drags on is anovulation, meaning your body didn’t release an egg that cycle. When you ovulate normally, your ovaries produce progesterone, the hormone responsible for stabilizing your uterine lining and triggering a clean, predictable shed. Without ovulation, progesterone never rises. The lining keeps building under the influence of estrogen alone, becoming thicker and less stable. When it finally breaks down, it does so unevenly, leading to prolonged, irregular bleeding that can start and stop over many days.
Anovulation is extremely common. It happens occasionally in most women, but it’s more frequent during times of hormonal transition: puberty, the years before menopause (perimenopause), after stopping birth control, and during periods of significant stress or weight change. Conditions like polycystic ovary syndrome (PCOS) also cause chronic anovulation. The bleeding you experience during anovulatory cycles isn’t technically a true period. It’s sometimes called abnormal uterine bleeding, but it feels and looks like a period to the person experiencing it.
Thyroid Problems Can Disrupt Your Cycle
Your thyroid gland plays a surprisingly large role in menstrual regularity. When thyroid function is off, it disrupts the chain of hormonal signals between your brain and your ovaries. Specifically, changes in thyroid hormone levels can alter the hormones that trigger ovulation, shift the balance of sex hormones circulating in your blood, and raise levels of prolactin, a hormone that can suppress normal cycling. Both an underactive thyroid (hypothyroidism) and an overactive one can cause heavy or prolonged periods, though hypothyroidism is more commonly linked to longer, heavier bleeding. A simple blood test can check your thyroid levels, and it’s one of the first things worth ruling out if your periods have changed.
Adenomyosis and Endometriosis
Two structural conditions frequently cause periods to last longer than normal. Adenomyosis occurs when the tissue that normally lines the uterus grows into the muscular wall of the uterus itself. This makes the uterus enlarged and boggy, leading to heavy bleeding, severe cramps, and periods that stretch well beyond the usual timeframe. It’s most common in women in their 30s and 40s, particularly those who have had children.
Endometriosis, a related but distinct condition, involves similar tissue growing outside the uterus, often on the ovaries, fallopian tubes, or pelvic lining. Its hallmark symptom is pelvic pain that worsens during your period, though heavy and prolonged bleeding is also common. The two conditions overlap significantly in symptoms, and some people have both. Diagnosis typically requires imaging (ultrasound or MRI for adenomyosis) or, in some cases, surgery for endometriosis. Both are manageable with hormonal treatments or, in more severe cases, surgical options.
Fibroids and Polyps
Uterine fibroids are noncancerous growths in or on the uterus, and they’re remarkably common. By age 50, the majority of women will have at least one. Most fibroids cause no symptoms at all, but those that grow near the uterine lining can distort the cavity and increase the surface area that bleeds during a period. The result is heavier flow and longer bleeding. Uterine polyps, which are small overgrowths of the endometrial lining, cause similar symptoms. Both can be identified with ultrasound and treated if they’re causing problems.
A Bleeding Disorder You Might Not Know About
This one surprises most people. Among young patients who present with heavy menstrual bleeding as their only symptom, inherited bleeding disorders are found in roughly two-thirds of cases. About 26% of those involve von Willebrand disease, a condition where the blood doesn’t clot as efficiently as it should. Many women with von Willebrand disease go undiagnosed for years because they assume their heavy, prolonged periods are just “how their body works.”
Clues that a bleeding disorder might be involved include periods that have been heavy and long since they first started, a personal history of easy bruising, nosebleeds, or prolonged bleeding after dental work or surgery, and a family history of similar symptoms. Screening involves a standardized bleeding assessment and blood tests that measure clotting factors. If your periods have always been unusually heavy and long, this is worth bringing up with your doctor, particularly if other types of bleeding have been a pattern in your life.
Your IUD Could Be the Cause
If your periods got longer after having an IUD inserted, the device itself is the likely explanation. Copper IUDs are well known for increasing menstrual bleeding. In one study tracking bleeding patterns over the first 90 days after insertion, copper IUD users reported a median of 26 days of bleeding total during that window. That’s nearly one out of every three days. The hormonal IUD (levonorgestrel) actually caused more irregular spotting days initially (a median of 38 days in the same 90-day period), though it typically reduces overall bleeding significantly after the first few months.
For copper IUD users, the increased bleeding and longer periods tend to improve somewhat over time but may never fully return to pre-insertion levels. For hormonal IUD users, the initial irregular bleeding usually settles within three to six months, and many women eventually have very light periods or none at all.
When Long Periods Become a Health Risk
A period that lasts too long isn’t just inconvenient. Chronic heavy bleeding drains your iron stores over time, often leading to iron deficiency anemia. Iron deficiency is defined as a ferritin level below 15 to 30 micrograms per liter, and anemia is diagnosed when hemoglobin drops below 120 grams per liter in premenopausal women. Symptoms include fatigue that doesn’t improve with sleep, shortness of breath during normal activity, dizziness, difficulty concentrating, and pale skin. Many women with heavy periods develop iron deficiency so gradually they don’t realize how much their energy and cognitive function have declined until it’s corrected.
Certain signs during a period warrant urgent attention. Soaking through one or more pads or tampons every hour for several consecutive hours, passing blood clots the size of a quarter or larger, or feeling faint and lightheaded from blood loss all indicate bleeding that needs prompt medical evaluation.
Figuring Out What’s Behind It
Because so many different conditions can cause prolonged periods, the evaluation usually starts broad and narrows down. Tracking your cycle length, bleeding duration, and flow intensity (how often you change pads or tampons) gives your provider useful baseline information. From there, common first steps include blood work to check thyroid function, iron levels, and hormone levels, along with a pelvic ultrasound to look for fibroids, polyps, or signs of adenomyosis.
If initial testing is unremarkable and your bleeding has been heavy since your teen years, screening for a bleeding disorder like von Willebrand disease is a reasonable next step. The key point is that prolonged periods almost always have an identifiable cause, and most of those causes respond well to treatment. Hormonal options (birth control pills, hormonal IUDs, or other hormonal therapies) address the majority of cases related to anovulation, hormonal imbalance, or structural conditions. When a specific problem like fibroids or polyps is found, targeted procedures can resolve the issue more directly.