Ferritin: Iron Stores and What the Test Shows
Iron deficiency is one of the most widespread micronutrient shortfalls in the world, and it’s disproportionately common in women of reproductive age. The paradox is that the classic marker — haemoglobin — can remain perfectly normal while the body’s iron stores are already depleted. That’s why doctors increasingly order ferritin alongside a complete blood count: it reflects the body’s actual iron reserves, not just the iron currently in transit. Knowing what the numbers on your report mean is a meaningful step toward understanding your health more accurately.
What Ferritin Is (vs. Hemoglobin and Serum Iron)
Ferritin is a storage protein that holds iron inside cells. A small amount circulates in the bloodstream at all times, and it’s this serum ferritin that the test measures — it reliably reflects the body’s total iron stores.
The three iron-related markers each measure something different. Haemoglobin is iron currently “on the job”: it binds oxygen inside red blood cells and carries it to tissues. Serum iron is the iron in transit through plasma — highly variable, shifting throughout the day in response to meals and stress. Ferritin is the reserve tank. As long as the tank isn’t empty, the body compensates for current demand and blood parameters stay in range.
A useful analogy: haemoglobin is the fuel in the engine right now; ferritin is how much is left in the tank. The engine keeps running until the tank runs dry — but checking the fuel level regularly is a good idea regardless.
Ferritin Reference Ranges
Reference values for ferritin vary considerably depending on sex, age, and physiological state. The lower limit for women differs between laboratories — anywhere from 10 to 30 ng/mL — due to differences in methodology and reagents.
| Group | Ferritin (ng/mL) |
|---|---|
| Men | 30 – 400 |
| Premenopausal women | 15 – 150 |
| Postmenopausal women | 30 – 300 |
| Pregnant (varies by trimester) | 10 – 150 |
| Children | 7 – 140 |
WHO guidance (2020): serum ferritin below 15 ng/mL indicates depleted iron stores in non-pregnant adults. An important nuance: in the presence of inflammation or infection, ferritin can appear falsely normal — a level below 70 ng/mL alongside elevated CRP may still indicate functional iron deficiency.
Low Ferritin: Iron Deficiency
Ferritin is the first marker to fall — often long before haemoglobin drops or red cell indices change. This stage is sometimes called “latent” or “hidden” iron deficiency: reserves are running out while the blood count still looks normal.
The symptoms of latent deficiency are easy to attribute to stress or overwork: chronic fatigue (the most common complaint), hair loss and thinning, brittle nails, restless legs syndrome, persistently cold hands and feet, difficulty concentrating — and occasionally pagophagia, an urge to chew ice or starch.
The most common causes in adults are heavy menstrual periods, pregnancy and breastfeeding, insufficient intake of haem iron (a particular concern for vegetarians and vegans), and chronic gastrointestinal blood loss — from ulcers, polyps, or colorectal cancer. That last cause is the one not to miss. It’s why doctors often investigate further when ferritin is low without an obvious explanation. Ferritin is usually assessed alongside the full CBC, including red cell indices such as MCV and MCH, for a complete picture.
High Ferritin: Possible Causes
A key fact that’s often overlooked: ferritin is an acute-phase protein. It rises in response to any inflammation in the body — from a common cold to a chronic condition. That means elevated ferritin on its own is not a diagnosis; it needs to be interpreted alongside inflammatory markers (CRP, ESR).
The main causes of high ferritin include: acute or chronic infection or inflammation; liver disease (alcoholic liver disease, non-alcoholic fatty liver disease); hereditary haemochromatosis — a genetic condition causing iron overload that requires specialist input; repeated blood transfusions; and metabolic syndrome.
A ferritin level above 1,000 ng/mL warrants clinical investigation regardless of the suspected cause. Even a moderate elevation without symptoms isn’t a reason to panic — it’s a signal to discuss the result with your doctor, not to take matters into your own hands.
How to Prepare for the Test
Ferritin testing is straightforward. Blood is usually drawn in the morning, either fasting or after a light meal — diet doesn’t meaningfully affect ferritin, but most laboratories recommend standard preparation when the test is part of a broader panel.
The critical point: avoid testing during an acute illness, active infection, or within one to two weeks of surgery or trauma. During these periods ferritin is falsely elevated by the acute-phase inflammatory response, and the result won’t reflect your true iron stores.
For iron-deficiency screening, doctors typically order serum iron, ferritin, and a CBC together. If you’re being assessed as part of a basic screening panel, these markers are often already included or added on the doctor’s recommendation.
Iron, Ferritin, and Transferrin Together
Serum iron is an instantaneous snapshot: how much iron is circulating in plasma right now. It’s highly unstable — it shifts throughout the day and after meals — so it’s only meaningful in combination with other markers.
Transferrin and TIBC (total iron-binding capacity) represent the transport protein and its maximum carrying capacity. When the body senses an iron shortage, it produces more transferrin to capture whatever iron is available: TIBC rises. Low ferritin combined with high TIBC is the classic pattern of iron deficiency.
Transferrin saturation (serum iron ÷ TIBC × 100) is normally 20–50%. A low value (below 16%) points to deficiency; a high value (above 45%) may suggest iron overload.
| Condition | Ferritin | Serum Iron | TIBC | Saturation |
|---|---|---|---|---|
| Iron deficiency | Low | Low | High | Low |
| Iron deficiency with inflammation | Normal/Low | Low | Normal/Low | Low |
| Hemochromatosis | High | High | Normal/Low | High |
When to Retest
After starting iron supplementation, a follow-up test is typically done at 8–12 weeks — that’s how long ferritin takes to respond. Haemoglobin usually recovers sooner, often within 4 weeks.
During pregnancy with an initially low ferritin, retesting each trimester (or per the obstetrician’s guidance) is standard practice.
For people in at-risk groups — women with heavy periods, vegetarians, anyone with chronic gastrointestinal conditions — annual monitoring makes sense. Ferritin changes slowly, reflecting gradual shifts in iron reserves, so monthly testing adds no value. A practical approach is to check it alongside fasting glucose in an annual check-up: a single visit, a fuller picture.
When to See a Doctor
Most ferritin abnormalities don’t require urgent action, but some situations do call for a prompt conversation with your doctor.
See your GP or general practitioner if:
- Ferritin is below 15 ng/mL — investigate the cause (menstrual losses, diet, a gastrointestinal source). Don’t self-treat.
- Ferritin is above 300–400 ng/mL with no obvious inflammatory explanation — investigation is needed to rule out liver disease or haemochromatosis.
- You have symptoms: persistent unexplained fatigue, unexplained weight loss, unusual bleeding, or abdominal pain.
- You’re pregnant with low haemoglobin or ferritin — always escalate to your obstetrician.
The dose and duration of iron therapy are determined by a doctor after confirming deficiency and identifying the cause. Self-prescribing iron supplements can mask a serious underlying condition.
How HealthLab Helps You Track Ferritin
Ferritin is most informative as a trend: a single result tells you much less than comparing “before treatment” → “8 weeks in” → “6 months later.” Seeing whether iron stores have actually recovered after a course of supplements — or whether deficiency returns every autumn — is a question that a trend chart answers and a lone data point cannot.
HealthLab automatically recognises ferritin and other biomarkers from PDF lab reports issued by any laboratory and builds a trend chart over time. You can see the full picture at a glance — without manual data entry or spreadsheets.
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Frequently Asked Questions
Why is the normal ferritin range lower for women than for men?
Physiologically, women have smaller iron stores because of monthly menstrual losses, and higher iron demands during pregnancy and breastfeeding. Heavy periods are the most common cause of iron deficiency in women of reproductive age worldwide. That’s why the reference range for premenopausal women is lower — and why a ferritin that’s formally “normal” at 20–25 ng/mL can still be accompanied by real deficiency symptoms.
Can I test for ferritin during my period?
Yes. Unlike haemoglobin, which can temporarily dip during or immediately after menstruation, ferritin isn’t meaningfully affected by the phase of your menstrual cycle. Choose whatever day is convenient. The one restriction applies to everyone: avoid testing during an acute illness or active inflammation (fever, a cold or flu) — ferritin will be falsely elevated by the acute-phase response, and the result won’t reflect your actual iron reserves.
How can ferritin be low when hemoglobin is normal?
Because the body depletes its iron stores (ferritin) first, before blood parameters are affected. This is called latent or hidden iron deficiency: reserves are at a minimum, but the body is still compensating — haemoglobin and red cell indices remain normal. It’s a real, clinically meaningful, and very treatable condition. Dismissing it because “haemoglobin is fine” isn’t the right approach.
Should I take iron supplements on my own?
It’s strongly advisable not to. First, the wrong dose can cause significant gastrointestinal side effects — nausea, constipation, abdominal cramping. Second, self-treating can mask a serious underlying cause: low ferritin from a bowel polyp or tumour needs a completely different response, not just an iron course. Third, excess iron is toxic. Always confirm iron deficiency with blood tests and agree on a treatment plan with your doctor.
My ferritin is elevated but I have no symptoms — what should I do?
The first step is to repeat the test 2–4 weeks later, well clear of any acute illness or inflammatory state — even a minor cold can push ferritin up. If the elevation persists, see your doctor: they’ll likely order inflammatory markers (CRP, ALT, AST, ESR) and, if needed, transferrin saturation and genetic testing for haemochromatosis (HFE mutations). Asymptomatic persistently elevated ferritin isn’t a reason to panic — but it is a reason to investigate.
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