A period lasting more than seven days is classified as heavy menstrual bleeding, sometimes called menorrhagia. The typical period lasts four to five days, with total blood loss of about two to three tablespoons. If yours regularly stretches past a week, something is usually driving that extra bleeding, whether it’s a hormonal imbalance, a structural issue in the uterus, or a side effect of contraception.
How Long Is Too Long?
Seven days is the clinical cutoff. Periods lasting longer than that are considered abnormally heavy, and they often come with heavier flow too. People with heavy menstrual bleeding typically lose about twice as much blood as average. Other signs your bleeding has crossed into heavy territory include soaking through a pad or tampon every hour for several consecutive hours, needing to double up on pads, passing blood clots the size of a quarter or larger, or having to change pads overnight.
A single longer-than-usual period can happen to anyone and isn’t necessarily a problem. But if your periods consistently run past seven days, or you’re noticing the heavy-flow signs above, there’s likely an underlying reason worth identifying.
Hormonal Imbalances
The most common explanation for prolonged periods is a disruption in the balance between estrogen and progesterone, the two hormones that control how your uterine lining builds up and sheds each month. Normally, estrogen thickens the lining during the first half of your cycle, and then progesterone stabilizes it and triggers an organized, time-limited shed. When that system breaks down, bleeding drags on.
If you don’t ovulate during a cycle (something called anovulation), your body keeps producing estrogen without the progesterone surge that follows ovulation. The lining keeps growing in a disorganized way, and without progesterone to coordinate the shedding process, pieces of it break off at random intervals instead of all at once. The blood vessels in the lining don’t constrict the way they normally would, and bleeding can become both heavier and longer.
Anovulation is especially common during puberty, the years leading up to menopause (perimenopause), and in people with polycystic ovary syndrome (PCOS). Stress, significant weight changes, and intense exercise can also suppress ovulation and throw off this hormonal balance.
Thyroid Problems
Your thyroid gland plays a quiet but important role in regulating your menstrual cycle. When it’s underactive (hypothyroidism), periods can become longer, heavier, and more irregular. Studies have found that anywhere from 23% to 68% of people with hypothyroidism experience menstrual irregularities, with the variation depending on how the condition is defined and how severe it is. An overactive thyroid can also disrupt your cycle, though it more commonly causes lighter or missed periods rather than prolonged ones.
Thyroid issues are diagnosed with a simple blood test, and treating the underlying thyroid problem usually brings periods back to a normal pattern over time.
Uterine Fibroids and Polyps
Fibroids are noncancerous growths in or on the uterus, and they’re extremely common. Many cause no symptoms at all, but those that grow into the uterine cavity can increase the surface area of the lining and interfere with the uterus’s ability to contract and stop bleeding. The result is periods that are both longer and heavier. Uterine polyps, which are smaller growths on the lining itself, can cause similar prolonged bleeding and spotting between periods.
Both fibroids and polyps are typically detected through ultrasound. Treatment depends on how much they’re affecting your quality of life and can range from hormonal management to minor procedures that remove the growths.
Your IUD or Contraceptive Method
If your periods got longer after starting a new form of birth control, that’s a likely culprit. Copper IUDs are well known for making periods heavier and longer, especially in the first several months after insertion. These side effects typically ease up after three to six months, but for some people, heavier bleeding persists for as long as the device is in place.
On the flip side, progesterone-only contraceptives (the mini-pill, the hormonal shot, or the implant) can sometimes cause prolonged, irregular bleeding or spotting. This happens because without enough estrogen to maintain the uterine lining, it becomes thin and fragile, leading to frequent low-level bleeding. This pattern is different from a true heavy period but can feel like your bleeding never fully stops.
Other Possible Causes
Endometriosis, where tissue similar to the uterine lining grows outside the uterus, can cause longer and more painful periods along with spotting before and after the main flow. Adenomyosis, a related condition where that tissue grows into the muscular wall of the uterus, is another common cause of prolonged, heavy bleeding and is particularly prevalent in people over 35.
Bleeding disorders also deserve a mention. Conditions like von Willebrand disease affect the blood’s ability to clot properly and can cause periods that are heavy from the very first one in adolescence. If you’ve always had long, heavy periods and also bruise easily, bleed excessively from dental work or cuts, or have a family history of bleeding problems, a clotting disorder is worth investigating.
Rarely, prolonged bleeding can signal something more serious like precancerous changes or cancer of the uterine lining. This is more relevant for people over 45, those with a long history of irregular periods, or those with risk factors like obesity. It’s not the most likely explanation, but it’s one of the reasons persistent changes in your bleeding pattern are worth evaluating.
What to Expect at the Doctor
If your periods regularly last more than seven days, an evaluation usually starts with blood work to check your hormone levels, thyroid function, and iron levels (since chronic heavy bleeding commonly leads to iron-deficiency anemia). A pelvic ultrasound can identify fibroids, polyps, or other structural causes. In some cases, a thin scope is used to look directly inside the uterus for a clearer picture.
Treatment depends entirely on the cause. For hormonal imbalances, hormonal therapy is the standard first-line approach. This might mean birth control pills, which regulate the cycle and thin the lining, or a hormonal IUD, which delivers progesterone directly to the uterus and dramatically reduces bleeding for most people. For structural problems like fibroids or polyps, the options range from these same hormonal treatments to minor procedures that remove the growths. If a thyroid problem or bleeding disorder is identified, treating that underlying condition often resolves the period issues on its own.
One thing to watch for: if you’re soaking through a pad or tampon every hour for more than two hours straight, feeling dizzy or lightheaded, or passing very large clots, that level of bleeding warrants urgent medical attention rather than a routine appointment.