Life stage

Period health: cycles, heavy periods and PMS

A typical menstrual cycle is often described as around 28 days, but a normal range is much wider, from about 21 to 35 days. Heavy periods (menorrhagia) are covered by NICE guideline NG88, and the standard first step for assessment is a diary tracking flow and any clots or flooding across at least two cycles. PMS is common and usually eases once a period starts; PMDD is a more severe, less common condition, and the two are covered in more detail on our dedicated PMDD vs PMS guide. This is information, not medical advice.

The menstrual cycle, briefly

A typical cycle is often described as around 28 days, but a normal range is much wider, from about 21 to 35 days, and it is also normal for length to vary somewhat from month to month. Rather than comparing yourself to a fixed number, it is more useful to know your own usual pattern, since a change from your own normal is often what is worth flagging to a GP.

Heavy periods (menorrhagia)

Heavy menstrual bleeding, sometimes called menorrhagia, is covered in the UK by NICE guideline NG88 on heavy menstrual bleeding assessment and management (nice.org.uk/guidance/ng88). If bleeding is affecting your daily life, work or wellbeing, that is reason enough to see a GP, regardless of how it compares to anyone else's experience.

The NHS-recommended way to help a GP assess heavy bleeding is to keep a diary tracking your flow (light, medium or heavy) and any clots or flooding across at least two cycles before your appointment. This gives a clearer picture than trying to describe it from memory, and it is worth starting the diary as soon as you notice a pattern that concerns you rather than waiting for the appointment to be booked.

PMS (premenstrual syndrome)

The NHS describes premenstrual syndrome (PMS) as the physical and emotional symptoms that many women experience in the days before a period, including mood changes, bloating, breast tenderness, irritability and low energy (nhs.uk/conditions/pre-menstrual-syndrome). PMS is common, and for most women symptoms ease once a period starts.

A minority of women experience something more severe than typical PMS, where premenstrual mood symptoms seriously affect daily life, relationships or work. This is a distinct, recognised condition called PMDD (premenstrual dysphoric disorder). We cover what distinguishes it, why the cycle-linked timing matters, and when to see a GP in our dedicated guide: PMDD vs PMS.

Read more

• Trying to conceive: preconception nutrition and NHS-recommended supplements.
• Perimenopause: the transition years and what changes.
• Menopause: symptoms, evidence and what helps.
• Iron for women: heavy bleeding can contribute to iron loss, so this is worth reading if your periods are heavy.

Frequently asked questions

This is information, not medical advice, and is not a substitute for a registered clinician. If you are concerned about your periods, cycle or mood, speak to your GP.

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Iron Strips

Heavy periods can contribute to iron loss, as noted above. Her Vitals' own iron is an oral dissolving strip rather than a capsule, providing 19 mg of iron (as ferric saccharate) plus 400 mcg folate. That is above the NHS's 17 mg supplemental guidance, so confirm low iron with a blood test before starting, and see a GP if heavy bleeding is affecting your life.

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