Ferritin and heavy periods.

How many women, actually.

Several large U.S. and international studies place the prevalence of heavy menstrual bleeding at roughly 20% of menstruating women — about one in five. That's not the population of women who occasionally have a heavy day; that's the group meeting clinical criteria for HMB. By any reasonable count, this is among the most common chronic conditions affecting U.S. women in their reproductive years.

"One in five women bleed heavily enough to meet clinical criteria. Most have never been asked about it."

The downstream picture is just as consistent. Iron-deficiency anaemia is the most common nutritional deficiency in U.S. women of reproductive age. Iron deficiency without anaemia — ferritin low, haemoglobin still in range — is more common still, and routinely missed because standard annual panels don't include ferritin. The canonical ferritin guide covers what the marker measures; this page focuses on the menstrual side of the story.

What counts as heavy.

"Heavy" is one of the harder words in clinical conversation, because it is calibrated to what each woman has known. The clinical criteria are more concrete.

None of these are diagnostic by themselves. They are flags that a conversation with a qualified healthcare provider is worth scheduling. The heavy-periods hub walks through the broader symptom picture.

Why this gets missed.

The under-detection is the consistent finding. A few reasons, none flattering.

Normalisation.

Heavy bleeding has been normalised across multiple generations of women's health writing — "everyone has heavy months sometimes" — to the point where women often only realise their flow is unusual when they hear another woman describe theirs. The clinical criteria are not folk knowledge.

Ferritin isn't on the standard panel.

The default U.S. annual physical includes CBC, which measures haemoglobin and red cell indices. It does not include ferritin. Iron stores can be depleted for years before haemoglobin drops enough to flag anaemia. The signal of an early iron-depletion arc is invisible to CBC alone.

Symptoms map to multiple "causes."

Fatigue, hair shedding, brain fog, restless legs, exercise intolerance, palpitations on stairs — these are the classic symptoms of low iron. They are also the classic symptoms of low thyroid, low B12, perimenopause, depression, poor sleep and chronic stress. The differential is wide enough that "iron" can fall off the list before it's tested.

The bleeding question often doesn't get asked.

Time-pressured visits often skip the menstrual history, particularly when the visit was scheduled for something else. Women are often more willing to describe fatigue than to volunteer that they soak through overnight protection every cycle.

What a full iron workup looks like.

A useful workup pairs the CBC with full iron studies. A ferritin number alone, while better than nothing, is most informative read alongside the others.

A "low ferritin with low transferrin saturation and high TIBC" picture is classic iron deficiency. A "low ferritin with low TIBC" picture might suggest a different story — chronic disease, inflammation — and the workup adjusts accordingly. This is the kind of nuance a single ferritin can't deliver.

Iron supplementation, in plain English.

Three notes — all educational, not personalised guidance.

Forms.

Oral iron supplements are most commonly ferrous sulfate, ferrous fumarate, ferrous gluconate, ferrous bisglycinate (chelated forms) or polysaccharide-iron complexes. The forms differ in elemental iron content, absorption, and how well they're tolerated — chelated forms are often associated with fewer GI side effects, though they can be more expensive. The iron supplements review covers the four forms most worth comparing.

Vitamin C and absorption.

Non-heme iron (the form in plant sources and most supplements) is absorbed more efficiently in the presence of vitamin C. Some clinicians suggest taking iron supplements with a glass of orange juice or 200 mg of vitamin C. Conversely, calcium, coffee, tea and certain medications (PPIs, antacids) can blunt absorption — timing matters.

Every-other-day dosing — educational.

An emerging body of research suggests that alternate-day oral iron dosing may improve absorption and reduce GI side effects compared to daily dosing. The mechanism: daily iron transiently raises hepcidin, the hormone that blocks intestinal iron absorption, for roughly 24 hours. Spacing doses every other day may allow hepcidin to come down between doses, improving net absorption. This is a useful piece of context to bring to a conversation, not a personal protocol — the right schedule depends on degree of deficiency, tolerability and your provider's preferred approach.

IV iron.

For some women, oral iron is insufficient, poorly tolerated, or simply too slow to keep up with ongoing losses. IV iron under medical supervision is an option in these cases. The conversation about IV iron is one to have with a primary care physician, a haematologist, or a gynaecologist familiar with iron management.

When to escalate.

Persistent heavy menstrual bleeding deserves a workup. The standard list of causes a provider will work through generally includes:

• Structural: uterine fibroids, polyps, adenomyosis. Usually evaluated with pelvic ultrasound, sometimes saline-infusion ultrasound or MRI.
• Endocrine: thyroid dysfunction (both hypo- and hyperthyroidism can affect cycle), hyperprolactinaemia, PCOS-related cycle disruption.
• Coagulation: bleeding disorders such as von Willebrand disease — under-diagnosed in women, and worth considering particularly if heavy bleeding has been present since menarche.
• Pharmacological: anticoagulants, copper IUDs and certain other medications can increase bleeding.
• Pregnancy-related: miscarriage, ectopic pregnancy, retained tissue — always considered in the differential of acute changes.
• Malignancy: rare in younger women but always considered, particularly with intermenstrual or post-menopausal bleeding.

The work-up is not necessarily long or invasive — but it is worth having. The Royal College of Obstetricians and Gynaecologists (RCOG), the American College of Obstetricians and Gynecologists (ACOG) and other clinical bodies have explicit guidelines on HMB evaluation that your provider can draw on.

Questions to bring to your provider.