How Long Should a Period Last? The Honest Ranges

A typical period lasts about 2 to 7 days, and a typical adult menstrual cycle runs roughly 21 to 35 days from the first day of one period to the first day of the next. But "normal" here is defined less by hitting those numbers than by two other things: what is normal for you, and whether that has changed. Bleeding that regularly lasts more than 7 to 8 days is considered prolonged and warrants a look — not because a long period is automatically dangerous, but because it is a common signal of something specific and treatable underneath.

Almost every article on this question stops at the range. The range is the least useful part. What you actually need to know is why bleeding lasts as long as it does, because once you understand the mechanism, every abnormal pattern in this article stops being a random symptom and becomes a readable clue.

Why a period ends when it does: it is a repair time, not a drain time

A period is not the uterus emptying like a tank. It is a controlled demolition followed by a controlled rebuild, and the length of your bleed is essentially the length of the rebuild.

Here is the sequence. After ovulation, the collapsed follicle becomes the corpus luteum and produces progesterone. Progesterone acts on receptors in the endometrium (the uterine lining), converting it into a stable, secretory, "decidualised" tissue. If no pregnancy implants, the corpus luteum dies on schedule after roughly 11 to 14 days and progesterone falls off a cliff. That progesterone withdrawal is the trigger: it releases a cascade of matrix metalloproteinases — enzymes that dissolve the scaffolding holding the lining together — while the spiral arterioles feeding that lining clamp down and starve it of blood. The functional layer breaks up and is shed.

What stops the bleeding is the next cycle already starting underneath it. A new cohort of ovarian follicles begins producing estradiol, and estradiol acting on the surviving basal layer drives rapid re-epithelialisation — the raw surface is resurfaced from below. Bleeding stops when the floor is rebuilt, typically within a few days. Local haemostasis (platelet plugs, then fibrin) buys time while that happens.

So the honest answer to "how long should a period last" is: as long as it takes to shed a lining that was built under progesterone and to resurface the bed underneath it — usually 2 to 7 days. Every cause of a too-long or too-short period is a failure at one of those steps. Hold that in your head and the rest of this article reads itself. If you want the full cycle, see our menstrual cycle phases guide or the hormone anatomy tool.

The honest ranges, by duration

Cycle length — first day to first day — is the other half of the picture. Roughly 21 to 35 days is the adult range; teenagers in the first year or two after their first period, and women in perimenopause, both sit legitimately outside it. Track both numbers, not just one: our period and ovulation tracker and cycle explorer will do it for you.

Too long: what prolonged bleeding is actually telling you

Gynaecologists sort abnormal uterine bleeding into structural causes you can see on a scan and non-structural causes you cannot. Both change how long you bleed, by different routes.

Structural: fibroids, adenomyosis, polyps

Fibroids are benign smooth-muscle tumours of the uterine wall. The ones that matter most for bleeding are those bulging into the cavity: they enlarge the endometrial surface area, distort the arterioles that are supposed to constrict, and physically stop the uterus contracting down on itself to close off bleeding vessels. Adenomyosis is endometrial tissue growing inside the muscle wall itself — a boggy, enlarged uterus that contracts poorly and bleeds heavily and long, classically with worsening cramping. Polyps are focal overgrowths of lining with fragile surface vessels that bleed at the wrong times, often as spotting between periods as well as prolonged flow. See uterine fibroids, adenomyosis and uterine polyps.

The under-told one: bleeding disorders

This is the fact that most reproductive-health content skips. A meaningful minority of women with heavy menstrual bleeding — figures of roughly 1 in 10 to 1 in 5 are cited in specialist guidance — have an inherited bleeding disorder, and the commonest by far is von Willebrand disease. Von Willebrand factor does two jobs: it carries clotting factor VIII, and it is the molecular glue that lets platelets stick to damaged vessel walls. When it is deficient or dysfunctional, the raw endometrial bed cannot form platelet plugs efficiently — so the shed lining oozes for days longer than it should.

The reason this matters is that it is routinely missed. Women with a lifelong bleeding disorder have no comparison point: their heavy periods have always been their normal, so they never think to report them, and often their mother's periods were the same. Clues worth mentioning to a clinician: heavy periods since your very first one; easy bruising; frequent nosebleeds; prolonged bleeding after dental work, childbirth or surgery; a family history of any of the above. It is a blood test, not a mystery — and results are read against the testing laboratory's own reference range, because ranges vary by lab and by assay, and for cycle-dependent hormones (estradiol, progesterone, FSH, LH) they also depend on which day of the cycle the blood was drawn.

Thyroid disease

An underactive thyroid lengthens and heavies periods through several routes at once: it lowers sex hormone–binding globulin, disrupts the hypothalamic signalling that drives ovulation, raises prolactin, and reduces levels of several clotting factors including von Willebrand factor. An overactive thyroid tends to do the opposite — short, light, or absent periods. If your period changed and you are also exhausted, cold, constipated, or losing hair, read thyroid or menopause and thyroid problems in women.

Anovulation and unopposed estrogen — the perimenopause engine

Go back to the mechanism. If you do not ovulate, there is no corpus luteum, therefore no progesterone, therefore no synchronised progesterone withdrawal. But estradiol keeps coming. The lining goes on proliferating unopposed — thickening, outgrowing its own blood supply, becoming structurally fragile — and then sheds when and where it happens to break down: patchy, disorganised, unpredictable and often torrentially heavy, with no clean signal to start and no coordinated repair to stop. That single mechanism explains anovulatory bleeding in PCOS at 27 (see PCOS) and the flooding perimenopausal period at 47 (see irregular periods in perimenopause). It is also why unopposed estrogen sustained over years raises endometrial cancer risk — the lining never gets its progesterone-driven reset.

What "heavy" actually means — because the word is useless without a yardstick

Women systematically under-report heavy bleeding, for the simple reason that nobody can see anyone else's. If your period has always been heavy, you assume everyone's is. Use these instead of a feeling:

• You soak through a pad or tampon every one to two hours for several hours in a row.
• You pass clots larger than a 10p coin (about the size of a quarter), especially repeatedly. Clots form when bleeding outpaces the uterus's natural anticoagulants. See period blood clots.
• You double up — a tampon plus a pad, or a cup plus period pants — because one product cannot hold it.
• You wake at night to change protection, or you bleed onto the bed.
• It limits your life: you plan work, travel, exercise or clothing around your period, or you have flooded through clothes in public.

That last one is the criterion modern guidelines actually care about. Heavy menstrual bleeding is now defined by its effect on your physical, social and emotional quality of life — not by a laboratory measurement of millilitres. If your period is running your calendar, it counts, and you do not need to prove it with a measuring cup. Our bleeding decoder will help you translate a pattern into what to ask about, and heavy periods covers the workup and the options.

Too short or too light

A one-to-two-day, light period can be completely normal and always has been for you. It can also mean the lining never got thick enough to shed much — which happens when:

• You use hormonal contraception. Progestin thins the endometrium by design; a shorter, lighter bleed (or none) is the expected pharmacology, not a sign that something is "building up". Never start, stop or change a contraceptive on the basis of an article — that is a conversation with a clinician.
• Energy availability is low. Under-eating relative to training load suppresses the hypothalamic GnRH pulse generator, so LH and FSH fall, follicles do not mature, estradiol stays low and the lining stays thin. Periods get scant, then late, then stop. This is a physiological signal, not a convenience.
• PCOS or thyroid disease. Both disrupt ovulation, and both can present as infrequent, scanty bleeding. See PCOS symptoms.
• Sustained stress. The same hypothalamic brake, pulled by a different lever. See stress and cortisol.
• Perimenopause. As the follicle pool shrinks, some cycles produce little estradiol and you get a short, light bleed — often sandwiched between cycles that do the opposite.

One caution about testing at midlife: a single blood test is a poor way to settle the question. FSH, LH and estradiol swing widely from cycle to cycle in perimenopause, so one "normal" or one "menopausal" result proves very little on its own. Your bleeding pattern, tracked over months, is the better data.

The midlife angle: erratic is expected, heavy is not

In perimenopause, both numbers come loose at once. The follicle pool is depleting, FSH climbs, and the ovary responds erratically: some cycles surge estradiol far above the premenopausal range, some barely produce any, and an increasing proportion do not ovulate at all. So your cycle may run 21 days, then 40, then 24; your period may last 3 days, then 9. Persistent cycle-length variability of a week or more is one of the formal markers used to stage the menopause transition. It is not a malfunction; it is the transition itself. Check where you are with the menopause stage quiz, and read perimenopause symptoms and perimenopause vs menopause.

But there is a line that must not be blurred, and it gets blurred constantly. Erratic is expected. Heavy and prolonged is not something to simply endure until it stops. "It's just your age" is not a diagnosis. Two reasons:

First, iron. Heavy periods are the commonest cause of iron deficiency in women, and the deficiency arrives long before the anaemia does. Iron leaves storage first: ferritin falls while haemoglobin is still perfectly normal. That is the phase where you are exhausted, breathless on stairs, foggy, cold, losing hair — and told your blood count is fine, because only the blood count was checked. Ask for ferritin, not just a full blood count, and note that ferritin reference ranges vary between laboratories and that ferritin also rises with inflammation, so it is interpreted alongside context, not in isolation. See low ferritin, iron deficiency in women, and our lab-results explainer.

Second, the endometrium. Repeated anovulatory cycles mean repeated unopposed estrogen, which is exactly the exposure that drives endometrial hyperplasia and, over time, endometrial cancer. Prolonged, heavy or unpredictable perimenopausal bleeding is precisely the pattern that gets a scan and, where indicated, a biopsy — not because it is usually sinister (it usually is not) but because that is how the uncommon serious cause is caught early, when it is highly treatable. See endometrial cancer signs and endometrial biopsy.

And the absolute rule: any bleeding 12 or more months after your final period is never normal and always needs evaluation. Not a spot, not a smear, not "just once". Most postmenopausal bleeding turns out to be benign — usually a thin, atrophic lining — but roughly 1 in 10 cases is endometrial cancer, and the great majority of endometrial cancers announce themselves this way, which is why it is the one symptom that always earns prompt assessment. Read postmenopausal bleeding. (Scheduled or breakthrough bleeding on hormone therapy is a different situation with its own rules — see bleeding on HRT — but it is still worth reporting rather than assuming.)

When to see a doctor

Book an appointment if any of these apply:

• Bleeding lasts more than 7–8 days, repeatedly.
• Your period is heavy by the yardstick above — soaking a pad or tampon every one to two hours, coin-sized clots, doubling up on protection, waking at night to change, or a period that restricts your life.
• Anything has clearly changed from your own long-standing baseline: longer, heavier, more painful, or bleeding between periods or after sex. See spotting between periods.
• Cycles shorter than 21 days or longer than 35 days in an adult who is not in the menopause transition; or periods that stop for 3 or more months without pregnancy.
• Any bleeding at all 12+ months after your final period. This week, not "next time I'm in".
• Symptoms of iron deficiency — fatigue, breathlessness on mild exertion, palpitations, hair shedding, restless legs, cracked corners of the mouth, or craving ice. Ask specifically for ferritin.
• Signs pointing to a bleeding disorder — heavy periods since your very first one, easy bruising, frequent nosebleeds, prolonged bleeding after dental work, childbirth or surgery, or a family history of the same.

Seek urgent care if you are soaking through a pad or tampon every hour for two hours or more, passing very large clots with light-headedness, or you feel faint, breathless or have chest pain while bleeding.

Take data, not adjectives. Two or three tracked cycles — start date, days of bleeding, products used per day, clots, and what you had to cancel — will get you further in a ten-minute appointment than any description of "heavy". Decide in advance what you want out of the visit, too: a ferritin level, a scan, or a name for what is happening.

This article is for information and does not replace individual medical advice. Do not start, stop or change any medication or contraceptive on the basis of it.