Soaking through products every hour, passing large clots, or bleeding for more than a week — heavy periods affect roughly 1 in 3 women and are always worth investigating.
Heavy menstrual bleeding — medically known as menorrhagia — is one of the most common reasons women visit their GP. Yet many people assume that heavy periods are something they simply have to endure. In reality, heavy bleeding often has an identifiable cause, and effective treatments exist for most of them.
Understanding whether your bleeding falls into the "heavy" category is the first step. Flow is subjective, and everyone's baseline is different — but there are clinical markers that help define when bleeding warrants attention.
Clinically, heavy menstrual bleeding is defined as blood loss of more than 80ml per cycle. Since measuring blood volume isn't practical, doctors use the following practical indicators:
If two or more of these apply to your periods consistently, speak to a doctor. Heavy bleeding that goes unaddressed can lead to iron deficiency anaemia, which affects energy, concentration, immune function, and overall wellbeing.
Heavy periods rarely appear out of nowhere. Here are the ten most common underlying causes, ranging from hormonal imbalances to structural changes in the uterus.
The uterine lining (endometrium) is built up each cycle under the influence of oestrogen and then shed when progesterone levels drop. When this hormonal interplay is disrupted — for example, if ovulation doesn't occur — the lining can become thicker than usual, resulting in heavier bleeding when it eventually sheds. Hormonal imbalances are particularly common at the extremes of reproductive life: in the years after the first period begins (when ovulation isn't yet consistent) and in the perimenopausal transition (when ovulation becomes less frequent). Thyroid dysfunction and elevated prolactin can also disturb this balance.
Fibroids are non-cancerous growths made of muscle and fibrous tissue that develop within or around the wall of the uterus. They are extremely common — affecting up to 70% of women by the age of 50 — though many cause no symptoms at all. Fibroids that grow into the uterine cavity (submucosal fibroids) or that are embedded within the muscle wall (intramural fibroids) are most associated with heavy bleeding. They can also cause prolonged periods, pressure or pain in the pelvis, and frequent urination. Fibroids are typically diagnosed by ultrasound.
Uterine polyps are small, soft growths that form on the inner lining of the uterus (endometrium). Unlike fibroids, they are made of endometrial tissue rather than muscle. They can cause heavy or irregular periods, bleeding between periods, and spotting after sex. Polyps are usually benign but in rare cases can be precancerous — which is one reason they're worth investigating. They are diagnosed via ultrasound or hysteroscopy and are typically removed with a simple outpatient procedure. Removal usually resolves the associated heavy bleeding.
Adenomyosis occurs when the tissue that normally lines the uterus (endometrium) grows into the muscular wall of the uterus (myometrium). This causes the uterine wall to thicken, leading to heavy, prolonged, and often very painful periods. The uterus itself may become enlarged and tender. Adenomyosis is most common in women in their 40s and those who have had children, though it can occur at any age. It often co-exists with endometriosis. Diagnosis is increasingly made via MRI or specialist ultrasound, and treatment options range from hormonal therapies to surgery.
PCOS causes irregular or absent ovulation. When ovulation doesn't occur regularly, the uterine lining continues to build up under the influence of oestrogen without the opposing signal from progesterone that would normally trigger a timely shed. When a period does eventually arrive, the lining that has built up over a longer period sheds all at once — resulting in a heavier than usual bleed. This is why people with PCOS may experience long gaps between periods followed by very heavy bleeding episodes.
The thyroid gland regulates metabolism and its hormones interact closely with reproductive hormones. An underactive thyroid (hypothyroidism) is a frequently overlooked cause of heavy, prolonged periods. When thyroid hormone levels are low, the hormones controlling the menstrual cycle become imbalanced, often leading to irregular, heavier, or more frequent periods. Other signs of hypothyroidism include fatigue, weight gain, feeling cold, constipation, and dry skin. A simple blood test (TSH and free T4) can detect a thyroid disorder, and treatment with thyroid hormone replacement typically normalises periods.
Von Willebrand disease is the most common inherited bleeding disorder, affecting roughly 1% of the population — and many cases are undiagnosed. It impairs the blood's ability to clot properly, which can manifest as heavy menstrual bleeding from the very first period. Other clotting disorders, including platelet dysfunction and haemophilia carrier status, can also cause heavy periods. This cause is often missed because it's not routinely tested for; if you have always had very heavy periods and have a personal or family history of easy bruising or prolonged bleeding, ask your doctor about testing for a bleeding disorder.
The copper IUD (intrauterine device) is a highly effective non-hormonal contraceptive — but it is well-documented that it can increase menstrual flow, particularly in the first several months after insertion. The copper works partly by causing a local inflammatory reaction in the uterus, which can increase prostaglandin production and result in heavier, longer, and often more crampy periods. For many people this settles somewhat after six to twelve months, but for others heavier periods persist for as long as the IUD remains in place. This is important to factor in when choosing a contraceptive method.
As the body transitions toward menopause — a process that can span several years — fluctuating oestrogen and progesterone levels cause the menstrual cycle to become increasingly unpredictable. Cycles may become shorter or longer, and periods may become heavier before eventually stopping. Skipped ovulation (anovulatory cycles) becomes more frequent, allowing the endometrium to build up and then shed more heavily. While perimenopausal heavy bleeding is common, any sudden worsening of bleeding in women over 40 should be evaluated to rule out endometrial hyperplasia or other uterine changes.
Anticoagulant medications — such as warfarin, rivaroxaban, apixaban, or heparin — reduce the blood's ability to clot, which can significantly worsen menstrual bleeding. Aspirin at higher doses has a similar effect. If you've started a new medication and noticed a corresponding increase in your menstrual flow, this connection is worth flagging with your prescribing doctor. In some cases the dose can be adjusted or an alternative contraceptive or cycle management strategy can be added alongside the anticoagulant. Never stop prescribed anticoagulants without medical guidance.
Track your flow heaviness, duration, and symptoms each month. Your data gives your doctor a clearer picture — and helps you spot when something has changed.
Start tracking free →When you see a doctor about heavy periods, they will typically start with a detailed history — asking about your cycle length and duration, the severity of your flow, any associated pain, and whether there have been any recent changes. They will also ask about your personal and family medical history and any medications you take.
Common investigations include:
Treatment is tailored to the underlying cause, your age, whether you want to preserve fertility, and the severity of your symptoms. Options include:
Tranexamic acid is a non-hormonal medication taken only during your period. It works by stabilising the clotting mechanism in the uterus, reducing blood flow by up to 50% in many women. It does not affect fertility and can be taken alongside other medications. It is usually the first-line treatment for heavy bleeding without an obvious structural cause.
The combined oral contraceptive pill thins the uterine lining over time, leading to significantly lighter periods — often with less pain too. The progestogen-only pill and hormonal implant can also reduce or stop periods in many users. These options also provide contraception, making them particularly suitable for those who don't wish to become pregnant.
The Mirena is a small T-shaped device inserted into the uterus that releases a low dose of levonorgestrel (a progestogen) locally. It is highly effective at reducing heavy bleeding — around 80% of users experience significantly lighter periods, and many find their periods stop altogether within the first year. It also provides contraception for up to five years and is one of the most recommended long-term treatments for menorrhagia.
When medical management is insufficient or not suitable, surgical options are available. Endometrial ablation destroys the uterine lining using heat, cold, or microwave energy — resulting in lighter periods or none at all. It is a day procedure but is only suitable for those who have completed their family, as pregnancy after ablation is not recommended. Myomectomy (fibroid removal) and polypectomy (polyp removal) address specific structural causes. Hysterectomy — removal of the uterus — is a definitive cure but is typically reserved for severe cases that haven't responded to other treatments.
Yes — heavy menstrual bleeding is the most common cause of iron deficiency anaemia in women of reproductive age. When you bleed heavily each month, your body may not be able to replenish iron stores fast enough, leading to depleted levels over time. Symptoms of iron deficiency anaemia include fatigue, weakness, breathlessness, pale skin, difficulty concentrating, and hair loss. If you have heavy periods and experience these symptoms, ask your doctor for a blood test to check your full blood count and ferritin levels. Iron supplementation alongside addressing the underlying bleeding is the usual approach.
Small clots (smaller than a 50p coin) during the heaviest days of your period are considered normal. They form when blood pools in the uterus and the body's natural anticoagulants can't break them down fast enough. Larger clots, or clots passed regularly throughout your period, suggest you may be losing more blood than is typical. If you frequently pass clots the size of a 50p coin or larger, this is worth mentioning to a doctor — it's a useful marker for distinguishing heavy from normal flow.
Perimenopausal changes frequently cause heavier and more irregular periods for women in their 40s. However, heavy periods after 40 should not simply be assumed to be "normal" age-related changes without investigation. This age group also has a higher incidence of fibroids, adenomyosis, and endometrial thickening. Any sudden or significant worsening of bleeding in your 40s warrants at least a pelvic ultrasound and a conversation with your GP. Most causes are very manageable once identified.
Yes — the Mirena IUD (hormonal coil) is one of the most effective treatments for heavy menstrual bleeding available. It releases a small amount of progestogen directly into the uterus, thinning the lining and dramatically reducing blood flow. Studies show it reduces bleeding by around 80–90% in most users, and many women find their periods stop entirely within a year of insertion. It is a long-acting reversible contraceptive (effective for up to five years) and is recommended by NICE in the UK as a first-line option for heavy periods.
Seek emergency care if you are soaking more than one thick pad per hour for several consecutive hours and feel faint, dizzy, or significantly weak. These may be signs of acute blood loss requiring immediate medical attention. Also seek emergency care if you are pregnant and experiencing heavy bleeding, as this can indicate a miscarriage or ectopic pregnancy. Outside of these acute situations, heavy periods that are a recurring issue are best addressed with a planned GP appointment rather than emergency care.