How to recognise heavy bleeding
The UK's National Health Service (NHS) lists these signs:
- changing your pad or tampon every one to two hours
- needing two period products at the same time
- periods lasting longer than seven days
- blood clots larger than about 2.5 cm
- bleeding through to clothes or bedding
- avoiding exercise or daily activities, or taking time off
- often feeling tired or short of breath
Why it's more than a nuisance
Heavy menstrual bleeding is one of the main reasons for iron deficiency in women, with and without anaemia. A 2023 review describes both as common and often dismissed as normal – by those affected as much as in doctors' surgeries. Both cost quality of life: the bleeding on the days of your period, the iron deficiency every day.
Why a normal blood count isn't enough is explained in our article on iron deficiency without anaemia.
What can be behind it
A 2025 meta-analysis looked at which causes are found in heavy bleeding when none is known at first. In 30% it was a bleeding disorder, such as von Willebrand disease – 39% in adolescents, 16% in adults. Thyroid disorders and polycystic ovary syndrome (PCOS) also occurred.
Heavy bleeding is also one of the common symptoms of endometriosis.