Single marker guide · Ferritin (iron stores)
Ferritin is the measure of how much iron your body has in storage, and it is the most common explanation for tiredness, hair shedding and breathlessness that "normal" blood tests keep missing. Many UK laboratories only flag it below 15 µg/L. Symptoms start well above that, and dermatologists want it over 70 before hair regrows. The gap between those numbers is where most iron deficiency lives.
Venous draw at 103 UK clinics or at home. UKAS-accredited laboratory. Report reviewed by a medical professional.
The short answer
Iron deficiency happens in stages. First your stores run down, which ferritin shows. Only later, once the stores are gone, does haemoglobin fall and anaemia appear on a standard blood count. The NHS full blood count checks haemoglobin, so it catches the last stage and misses the first. You can be exhausted, shedding hair and short of breath on stairs with a perfectly normal haemoglobin, because the problem is still at the storage stage.
Ferritin also has a trap of its own. It rises with inflammation, infection, fatty liver and heavy drinking regardless of iron, so a "normal" ferritin in someone with inflammation can be hiding a deficiency. That is why we test it alongside CRP, the full iron studies and a blood count, never on its own. One number tells you your stores. Five numbers tell you whether to believe it.
Reference ranges
| Ferritin result | Category | What it means |
|---|---|---|
| Below 15 µg/L | Depleted | Stores are essentially empty. The level most laboratories flag. Anaemia is likely or imminent, and treatment is needed. |
| 15 to 30 µg/L | Deficient | British Society for Haematology guidance defines iron deficiency as ferritin below 30. Often reported as "normal" by labs with a lower cut-off, which is how it gets missed. |
| 30 to 50 µg/L | Low stores | Not deficient by definition, but tiredness, hair shedding, restless legs and poor exercise recovery are common here, especially in women and endurance athletes. |
| 50 to 150 µg/L | Optimal | Comfortable stores. Dermatologists target above 70 for hair regrowth; restless legs guidance targets above 75. |
| 150 to 300 µg/L | Upper normal | Fine for most men. In women, or with a raised CRP or liver enzymes, worth understanding why. |
| Above 300 µg/L | Raised | Usually inflammation, fatty liver or alcohol rather than iron overload. If transferrin saturation is also above 45%, haemochromatosis needs ruling out with your GP. |
Laboratory ranges vary and many still use a lower limit of 13 to 15 µg/L. TrueVitals reports show your result against both the laboratory range and the optimal range, with the reasoning written out.
Symptoms
Iron carries oxygen and drives energy production inside cells. Low stores feel like a persistent heaviness that sleep does not fix. Ferritin is tested in fewer than one in ten NHS fatigue investigations, which is why so many tired people are told their bloods are fine. Always tired but tests normal?
Hair follicles are among the first tissues to lose out when iron is short. Diffuse shedding, a widening parting and more hair in the plughole are classic, and most people never think to test iron for it. Hair loss blood test guide.
Less iron means less oxygen delivered per heartbeat, so the heart works harder. Breathlessness on mild exertion and a pounding or racing pulse are the signs, and they often appear before haemoglobin drops.
An uncomfortable urge to move your legs at night is strongly linked to low iron stores in the brain. Sleep specialists treat restless legs with iron when ferritin is below 75, well inside most laboratories' "normal" range.
Iron is needed to make dopamine and to fuel the brain, which uses a fifth of your oxygen. Poor concentration, low motivation and flat mood are common with low stores and lift when they are corrected.
Endurance athletes lose iron through sweat, foot-strike red cell damage and gut microbleeds. Performance drops 3 to 4% before anaemia appears, which is why serious runners test ferritin routinely. Blood test for runners.
Who runs low
Women lose iron every month, and heavy periods are the single biggest cause of low ferritin in the UK. Pregnancy and breastfeeding draw stores down further. Vegetarian and vegan diets supply iron in a form the gut absorbs poorly, and tea, coffee and calcium taken with meals cut absorption again. Endurance training, regular blood donation, coeliac disease, inflammatory bowel disease and long-term use of acid-reducing medication all push the same way. Women's health blood test guide.
One group needs a different conversation. If you are a man, or a woman past the menopause, and your ferritin is low with no obvious dietary reason, the cause is usually slow blood loss from somewhere in the gut. That is not a supplement question, it is a GP question, and your TrueVitals report says so plainly rather than leaving it in a footnote.
Read it in context
Ferritin on its own tells you your stores. Read alongside the right markers, it tells you whether that number is honest, how far the deficiency has progressed, and what is causing it.
Ferritin rises with inflammation. A ferritin of 60 with a raised CRP may be a true ferritin of 25. Without CRP beside it, a normal-looking ferritin can hide a deficiency completely. Every TrueVitals panel tests both.
The rest of the iron studies. Transferrin saturation shows how much iron is actually in circulation and ready to use; below 20% supports deficiency even when ferritin is borderline, and above 45% with a high ferritin points to iron overload.
Tells you which stage you are at. Normal haemoglobin with low ferritin is early deficiency. Small, pale red cells (low MCV and MCH) mean it has been going on long enough to affect production. Anaemia means the stores have been empty for months.
The other nutrients that build red cells, and they cause the same fatigue. Iron and B12 deficiency together is common in vegans and in coeliac disease, and each can mask the other on a blood count. B12 blood test guide.
An underactive thyroid slows iron absorption and causes heavier periods, so low ferritin and a sluggish thyroid often arrive together. Correcting one without checking the other is why some people's iron never seems to rise. Thyroid blood test guide.
Undiagnosed coeliac disease is a classic cause of iron deficiency that will not correct with tablets. At the other end, a high ferritin with raised ALT or GGT usually means a fatty liver rather than too much iron. Coeliac antibodies are in the Ultimate panel. Liver blood test guide.
Which test
Advanced
74 biomarkers · £269
Ferritin, serum iron, transferrin and saturation, with a full blood count, hs-CRP, B12, folate, vitamin D, full thyroid with Free T3 and antibodies, liver, kidney, lipids and hormones. The right choice if tiredness or hair loss is the question.
View AdvancedMost chosen
Ultimate
114 biomarkers · £349
Everything in Advanced plus coeliac screening, immunoglobulins, complete hormones, fasting insulin and HOMA-IR, Lp(a), tumour markers and urinalysis. The panel that finds why iron is low, not just that it is.
View UltimateSignature
230 biomarkers · £799
Processed by Randox. Extended cardiovascular, autoimmune, digestive and neurological screening on top of everything above. The deepest private panel in the UK.
View SignatureClinic draw £19 at 103 UK clinics. At-home phlebotomist £39 across 200+ areas. Fast from 10pm the night before. Pay monthly available.
Honest comparison
If you have already been diagnosed with iron deficiency and want to check that your supplements or infusion are working, a standalone finger-prick ferritin test from Medichecks costs around £39, and an iron profile with saturation around £49. For monitoring a known problem, that is the sensible spend.
A panel is the better choice when you are testing because of how you feel, when nobody has checked why your iron is low, or when you want the CRP, blood count, B12, thyroid and coeliac context that decides whether a ferritin number can be trusted. The Advanced panel works out at under £4 per marker and the report tells you what each result means and what to do about it. See how every UK provider compares.
After the result
Iron deficiency. Your report explains the likely cause from the rest of your results and what to tell your GP. For men and post-menopausal women this always warrants a GP conversation about where the iron is going, before or alongside treatment.
Low stores worth correcting. A gentle iron such as ferrous bisglycinate taken on alternate days absorbs better and causes less stomach upset than daily ferrous sulfate. Take it with vitamin C, away from tea, coffee, dairy and calcium. If heavy periods are the cause, treating those matters more than any supplement.
Ferritin rises slowly, around 10 to 20 µg/L a month with consistent supplementation. Three months shows whether you are absorbing it; if the number has not moved, the cause needs finding rather than the dose increasing. Your second report compares against your first automatically.
This page is general information, not medical advice. Do not take iron supplements long term without testing: iron overload is as real a problem as deficiency.
FAQs
Ferritin is the protein that stores iron inside cells, and the amount in your blood reflects the size of your iron reserves. It is the earliest and most sensitive indicator of iron deficiency, falling long before haemoglobin does. Because it also rises with inflammation, it is interpreted alongside CRP.
Laboratory ranges typically run from about 13 to 300 µg/L, but the British Society for Haematology defines iron deficiency as ferritin below 30. Most clinicians consider 50 to 150 optimal, with targets above 70 for hair loss and above 75 for restless legs. TrueVitals reports show both ranges.
Yes, in two ways. A result of 15 to 30 is labelled normal by many labs but is deficiency by clinical guidance. And because ferritin rises with inflammation, a raised CRP can lift a genuinely low ferritin into the normal range. Transferrin saturation below 20% helps confirm deficiency in both situations.
Most often inflammation, infection, fatty liver or regular alcohol, none of which mean iron overload. Genuine overload (haemochromatosis) is suggested when ferritin is high and transferrin saturation is above 45%, and needs a GP referral for genetic testing. Metabolic syndrome is a very common cause of moderately raised ferritin in the UK.
GPs generally order a full blood count for tiredness, which checks haemoglobin but not iron stores. Ferritin is added when anaemia is found or specifically requested. One audit found it included in under 10% of fatigue blood requests. If you want stores checked, ask for ferritin by name. What to ask your GP for.
Not for ferritin itself, though serum iron is best measured in the morning before iron tablets. TrueVitals panels also include glucose, insulin and lipids, so we ask you to fast from 10pm the night before and drink water as normal. Take any iron supplement after your draw, not before.
A standalone finger-prick ferritin test is around £39 and an iron profile around £49. A TrueVitals Advanced panel is £269 and includes full iron studies with 70 other markers, a full blood count, hs-CRP, B12, folate, thyroid and vitamin D, with a venous draw and a fully written report.
With consistent, well-absorbed supplementation, ferritin typically rises 10 to 20 µg/L a month, so getting from 20 to 70 takes three to four months. If it does not move, the cause is usually ongoing loss (heavy periods, gut bleeding) or poor absorption (coeliac disease, acid-reducing medication), which is why the cause matters more than the dose.
74 to 230 biomarkers. Venous draw at 103 UK clinics or at home. A report that tells you what your results mean and what to do next.
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