Skip to main content

Tests & procedures · UK

Iron screening for heavy periods

Why heavy periods so often cause iron deficiency, the tests that detect it before anaemia, and treatment options.

Key points

  • The screen pairs a full blood count with ferritin, the measure of iron stores, and sometimes full iron studies; ferritin detects deficiency long before anaemia appears on the blood count.

  • No fasting is essential, though morning samples are ideal; mention any iron supplements already taken, and recent illness, which falsely raises ferritin.

  • Results typically return within 1 to 2 working days.

  • A doctor should review results and, importantly, the periods themselves, since treating the iron without addressing the bleeding invites relapse.

About this test

Published 2026-09-27 · Next review 2027-09-27

Heavy menstrual bleeding is the most common cause of iron deficiency in younger women, and the deficiency stage before anaemia, low ferritin with a normal blood count, already causes fatigue, poor concentration, hair shedding and restless legs, yet is missed by a blood count alone. Anyone flooding, passing clots, or changing protection hourly deserves both the iron screen and a proper conversation about the bleeding, for which effective treatments exist.

Testing is available same-week via private GPs and labs, and gynaecology review for the bleeding itself, NHS or private, should follow where periods are genuinely heavy. Waiting lists for NHS outpatient assessment remain long in much of the UK, and many of these checks are not offered on the NHS at all unless you meet strict criteria. Private clinics can usually see you within days on a self-pay basis, with no GP referral needed in most cases.

Frequently asked

Common questions about Iron screening for heavy periods.

Quick, plain-English answers to what people ask us most.

  • What is an iron screen for heavy periods?

    This is a set of blood tests, usually including a full blood count, ferritin and sometimes other iron markers, used to check whether heavy menstrual bleeding has led to iron deficiency or anaemia.

  • Why would a doctor order this screen?

    Heavy periods are a common cause of iron deficiency, so this screen helps confirm whether symptoms like fatigue, breathlessness or dizziness are related to low iron, and to what degree, guiding whether treatment such as iron supplementation is needed.

  • Do I need to prepare for this test?

    No fasting is usually required, though it's helpful to mention the pattern and heaviness of your periods and whether you're currently taking any iron supplements, as this can affect interpretation.

  • What happens during the test?

    It's a simple blood draw from a vein in your arm, taking just a few minutes, with no special aftercare needed.

  • Does it hurt or carry any risks?

    There's minimal risk, similar to any standard blood test, with possible brief discomfort or a small bruise at the needle site.

  • How long do results take?

    Results are usually available within a few days, though this can vary depending on the laboratory and clinic.

  • What do abnormal results mean, and what happens next?

    Low ferritin or haemoglobin can confirm iron deficiency or anaemia related to heavy bleeding, in which case treatment might include iron supplements, dietary advice, or investigation and treatment of the underlying cause of heavy periods. Your doctor will discuss the best next step based on your specific results and symptoms.

  • Is this test available on the NHS, and how much does private testing cost?

    It's routinely available through the NHS as part of investigating heavy periods, though appointment availability can vary. Private testing typically offers results within days, reviewed by a doctor, with cost varying by provider.

  • How reliable is this iron screen?

    Combining several markers, such as ferritin alongside a full blood count, gives a more reliable picture of iron status than any single test alone, since ferritin especially can be affected by inflammation as well as iron levels.

  • How do I book this test privately?

    You can book a private blood test directly, often without a GP referral, with results typically reviewed by a doctor within a matter of days.