The short answer: There is no official optimal ferritin level for women. According to expert consensus, a ferritin below 30 µg/l means iron deficiency.[1] From 100 µg/l, iron deficiency is unlikely in otherwise healthy adults. That is the view of the German guideline on fatigue (DEGAM) and of the IMD Berlin laboratory, whose decision limits I use as my guide.[2,12] In between, from 30 to 100 µg/l, it depends on your symptoms, your transferrin saturation and your CRP.[12]
Even so, many women with a ferritin of 18 or 22 are told: “Everything’s normal.” That may be technically true and still not help you. Why becomes clear once you know how your iron metabolism works.
How your iron metabolism works
| Step | What happens there |
|---|---|
| Absorption in the gut | Iron is absorbed in the duodenum, the first section of the small intestine, and better from animal sources than from plant sources. Plant iron needs stomach acid to dissolve. The liver hormone hepcidin controls how much gets through: after a dose of iron it rises and slows down the next round of absorption.[3] |
| Handover into the blood | For iron to leave the gut cell and bind to transferrin, copper-containing enzymes are needed (hephaestin, ceruloplasmin).[14] |
| Transport in the blood | Transferrin carries iron to the cells. Transferrin saturation shows how fully loaded these transporters are. |
| Storage | Ferritin stores iron, mainly in the liver, spleen and bone marrow. The ferritin level in your blood reflects these stores.[4] To release iron again, the body needs vitamin B2, among other things.[15] |
| Use | Haemoglobin for oxygen transport, myoglobin in muscle, iron-containing enzymes for energy production and thyroid peroxidase (TPO) in the thyroid[5] |
Think of the iron in your blood as the cash in your pocket and ferritin as your bank account. Your pocket can be full while your account is empty. That is why serum iron on its own tells you very little.
The three stages of iron deficiency
| Stage | Findings | What you notice |
|---|---|---|
| 1 · Stores fall | Ferritin drops, transferrin saturation and haemoglobin still normal | often not much yet |
| 2 · Iron deficiency without anaemia | Ferritin and transferrin saturation low, haemoglobin normal | exhaustion, hair loss, lower stamina, shortness of breath on exertion, an urge to move the legs in the evening (restless legs syndrome)[6,7,12,16] |
| 3 · Iron deficiency anaemia | haemoglobin and MCV low as well | marked breathlessness on exertion, pallor, palpitations |
The key point: symptoms already start at stage 2. A routine blood count only picks up stage 3.
Ferritin cut-offs at a glance
| Ferritin | Who says so? | What it means |
|---|---|---|
| 10–15 µg/l | common lower limit on lab reports | lab reference; strongly dependent on the lab and method |
| below 30 µg/l | Canadian expert consensus (Delphi study);[1] IMD Berlin[12] | iron deficiency confirmed, treatment indicated |
| 30–50 µg/l | IMD Berlin[12] | iron deficiency likely, especially with symptoms or transferrin saturation below 20% |
| below 50 µg/l | randomised trial in 198 women[6] | iron eased fatigue even without anaemia |
| 50–100 µg/l | IMD Berlin[12] | iron deficiency possible, especially with inflammation or low transferrin saturation |
| below 70 µg/l | WHO, only with inflammation[8] | sign of iron deficiency despite an apparently normal level |
| below 75 µg/l | restless legs syndrome guidelines[16,17] | iron treatment recommended for restless legs |
| from 100 µg/l | DEGAM guideline on fatigue;[2] IMD Berlin[12] | iron deficiency unlikely in otherwise healthy people – this is what I go by |
The other iron markers
| Marker | Lab reference (example) | How to read it |
|---|---|---|
| Transferrin saturation | 15–45% | below 20% with a ferritin of 30–100 µg/l points to a deficiency that needs treatment;[12] my functional guide value 25–35% |
| CRP | below 5 mg/l | ferritin rises with inflammation and can hide a deficiency[4] |
| Haemoglobin, MCV | depends on the lab | only fall at stage 3; an MCV below 80 fl points to iron deficiency |
| Serum iron | 50–170 µg/dl (about 9–30 µmol/l) | fluctuates a lot, not meaningful on its own |
Lab reference: typical example values; your lab’s range applies. My functional guide value: based on experience from my coaching, not an official reference value.
What studies show about low ferritin symptoms
Fatigue: In a French study, 198 women aged 18 to 53 with fatigue, a ferritin below 50 µg/l and normal haemoglobin took either iron or a placebo for twelve weeks. Fatigue fell by 47.7 per cent with iron and by 28.8 per cent with placebo.[6]
Hair loss: In a meta-analysis of 36 studies with more than 10,000 participants, women with hair loss had markedly lower ferritin levels than women without. The authors conclude that women with hair loss may benefit from higher ferritin levels.[7]
Restless legs: In my coaching I very often see restless, tingling legs in the evening, easing only with movement, in women with a ferritin below 50 µg/l. Iron deficiency in the brain is considered one of the mechanisms behind restless legs syndrome. For this reason, the International Restless Legs Syndrome Study Group (IRLSSG) and the American Academy of Sleep Medicine recommend measuring ferritin and transferrin saturation in people affected, and starting iron even at a ferritin of 75 µg/l or below.[16,17]
Shortness of breath: The IMD Berlin laboratory lists shortness of breath, muscle weakness and lower stamina among the possible signs of iron deficiency.[12] Oxygen is carried not only in the blood but also in muscle, by iron-containing proteins.
Thyroid: Thyroid peroxidase contains haem and needs iron. Without enough iron it works more slowly, and the thyroid makes less T4.[5] On your results this shows up mainly as a low fT4; the control centre in the brain responds, and TSH rises. A meta-analysis of ten studies found lower fT4 and fT3 levels in iron deficiency.[10] In a study of 2,581 pregnant women, those with iron deficiency had a higher TSH and a lower fT4 than women with full stores.[11] That is why I always check iron stores in Hashimoto’s.
Why women are affected so often
Before the menopause, periods and pregnancies are the most common causes of iron deficiency anaemia.[4] In the years before the menopause, bleeding often becomes longer and heavier: in the US SWAN study, just over a third of women reported heavy bleeding lasting three or more days on at least three occasions.[9] Plant-based diets, intensive exercise and poor absorption in the gut add to this.[12]
After the menopause, and in men, things are different. Here, the cause of iron deficiency must always be investigated by a doctor; it may, for example, be bleeding in the digestive tract.[4]
When you take iron and your ferritin doesn’t go up
This is one of the most common questions in my coaching. Usually one of these causes is behind it:
| Cause | What happens |
|---|---|
| Hepcidin | Inflammation and daily dosing make hepcidin rise; it blocks absorption in the gut.[3] |
| Low stomach acid | Plant iron needs stomach acid. In a large study, new iron deficiency was more than twice as common with acid-suppressing medication taken for more than two years.[13] Inflammation of the stomach lining can also slow absorption.[12] |
| Gut disorders | Coeliac disease and inflammatory bowel disease are among the typical causes of iron deficiency.[12] |
| Copper deficiency | Without copper, the enzymes that hand iron over from the gut cell into the blood are missing.[14] |
| Vitamin B2 deficiency | There are indications that a lack of riboflavin impairs iron absorption and its release from the stores.[15] |
| How you take it | Coffee, tea or calcium at the same time slow absorption. |
If your level stays low despite taking iron, the cause needs to be checked by a doctor.
If your ferritin is low
- Have the cause checked. Heavy bleeding, diet, absorption problems or blood loss: work out with your doctor what is behind it.
- Don’t take iron on a hunch. Too much iron can do harm, especially with an iron overload disorder such as haemochromatosis.[4] Test first, then act on the result.
- Plan how you take it. In two randomised trials at ETH Zurich, women with empty stores (ferritin up to 25 µg/l) absorbed more iron when they took it as a single morning dose every other day: a cumulative 21.8 per cent instead of 16.3 per cent. Splitting it into two daily doses brought no advantage but did raise hepcidin.[3] Discuss the product and dose with your doctor.
- Plan a follow-up test. The authors of the fatigue study suggest checking your blood levels after about six weeks.[6]
Patterns I often see in my coaching
| Pattern | Typical findings | What may be behind it |
|---|---|---|
| Exhausted, blood count “fine” | Ferritin 15–40 µg/l, haemoglobin normal | iron deficiency without anaemia |
| Restless legs in the evening | Ferritin below 50 µg/l | iron deficiency making restless legs worse |
| Ferritin fine, still signs of deficiency | Ferritin 80 µg/l, CRP raised, transferrin saturation below 20% | inflammation hiding a deficiency |
| Thinning hair, borderline thyroid | Ferritin below 50 µg/l, fT4 at the lower end, TSH above 2.5 | iron deficiency slowing thyroid hormone production |
| Taking iron, level barely rises | acid-suppressing medication, bloating, daily dosing with coffee | check stomach acid, gut, hepcidin, copper or B2 |
These patterns are pointers from my coaching experience, not diagnoses.
Where to start
- My free self-check shows you whether your signs point more towards your thyroid, perimenopause or the stress axis. You’ll then receive the starter guide that matches your result.
- Your free clarity call: 20 to 30 minutes on Zoom. Together we look at where you stand and which next step suits you.
Frequently asked questions
Is a ferritin level of 20 normal?
According to many lab reports, yes, because the lower limit is often 10 to 15 µg/l. According to expert consensus, though, a level below 30 µg/l already means iron deficiency.[1] If you have symptoms, it’s worth talking to your doctor.
What ferritin level rules out iron deficiency?
From 100 µg/l, iron deficiency is unlikely in otherwise healthy adults, according to the German guideline on fatigue (DEGAM) and the decision limits of the IMD Berlin laboratory.[2,12] With inflammation, a deficiency can still be present above that; in that case, transferrin saturation helps to clarify things.
Are low ferritin and hair loss linked?
Yes. In a meta-analysis of 36 studies, women with hair loss had markedly lower ferritin levels than women without hair loss.[7] If your hair is getting thinner, always ask for ferritin to be tested, together with CRP.
Can low ferritin cause restless legs?
Iron deficiency is considered an important aggravating factor. Guidelines recommend measuring ferritin and transferrin saturation in people with restless legs and starting iron even at a ferritin of 75 µg/l or below.[16,17] In my coaching I very often see restless legs at levels below 50 µg/l.
Why is my ferritin not going up even though I take iron?
Common reasons are raised hepcidin, too little stomach acid (for example from acid-suppressing medication), a gut condition such as coeliac disease, and a lack of copper or vitamin B2.[3,12–15] Have the cause checked by your doctor.
Why should CRP be tested at the same time?
Ferritin rises with inflammation and can hide a deficiency.[4] When inflammation is present, the WHO considers a ferritin below 70 µg/l in adults to be a sign of iron deficiency.[8]
Should I take iron every day?
In studies, women with empty stores absorbed more iron when they took it as a single morning dose every other day.[3] Discuss the dose and product with your doctor.
Can ferritin be too high?
Yes. A high ferritin can point to inflammation, liver disease or iron overload.[4] Raised levels should always be checked by a doctor.
Read on
- Perimenopause, thyroid or iron deficiency?
- Always tired? These blood tests are worth checking
- Understanding your thyroid blood tests
This article does not replace medical advice. Diagnoses are made by your doctor; changes to medication belong in medical hands.
Sources
- Naveed K et al. Defining ferritin clinical decision limits to improve diagnosis and treatment of iron deficiency: a modified Delphi study. Int J Lab Hematol 2023;45:377–386. doi.org/10.1111/ijlh.14016 · Delphi expert consensus
- DEGAM: S3-Leitlinie Müdigkeit [S3 guideline: Fatigue]. AWMF reg. no. 053-002, version 2023-01 (valid until 31 December 2027), long version (recommendation 5.3.1; sections 4.2.1, 4.2.5, 4.2.6). register.awmf.org · Guideline (Germany)
- Stoffel NU et al. Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women. Lancet Haematol 2017;4:e524–e533. doi.org/10.1016/S2352-3026(17)30182-5 · Two RCTs
- Trost LB, Bergfeld WF, Calogeras E. The diagnosis and treatment of iron deficiency and its potential relationship to hair loss. J Am Acad Dermatol 2006;54:824–844. doi.org/10.1016/j.jaad.2005.11.1104 · Review
- Zimmermann MB, Köhrle J. The impact of iron and selenium deficiencies on iodine and thyroid metabolism. Thyroid 2002;12:867–878. doi.org/10.1089/105072502761016494 · Review
- Vaucher P et al. Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial. CMAJ 2012;184:1247–1254. doi.org/10.1503/cmaj.110950 · RCT (n = 198)
- Treister-Goltzman Y, Yarza S, Peleg R. Iron deficiency and nonscarring alopecia in women: systematic review and meta-analysis. Skin Appendage Disord 2022;8:83–92. doi.org/10.1159/000519952 · Meta-analysis (36 studies, n = 10,029)
- World Health Organization. WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations. Geneva 2020 (recommendation 1.2). ncbi.nlm.nih.gov/books/NBK569877 · Guideline (WHO)
- Paramsothy P et al. Bleeding patterns during the menopausal transition in the Study of Women’s Health Across the Nation (SWAN). BJOG 2014;121:1564–1573. doi.org/10.1111/1471-0528.12768 · Prospective cohort study (n = 1,320)
- Garofalo V et al. Relationship between iron deficiency and thyroid function: a systematic review and meta-analysis. Nutrients 2023;15:4790. doi.org/10.3390/nu15224790 · Meta-analysis (10 cross-sectional studies)
- Li S et al. The relationship between iron deficiency and thyroid function in Chinese women during early pregnancy. J Nutr Sci Vitaminol 2016;62:397–401. doi.org/10.3177/jnsv.62.397 · Cross-sectional study (n = 2,581)
- IMD Institut für Medizinische Diagnostik Berlin-Potsdam. Ferritin bei Eisenmangel und Eisenmangelanämie: Neue Entscheidungsgrenzen ermöglichen eine differenziertere Beurteilung [Ferritin in iron deficiency and iron deficiency anaemia: new decision limits allow a more differentiated assessment]. Diagnostik-Information Nr. 400, Version 1. imd-berlin.de · Laboratory information (based on Naveed 2023 and the Swiss Delphi consensus 2019)
- Lam JR et al. Proton pump inhibitor and histamine-2 receptor antagonist use and iron deficiency. Gastroenterology 2017;152:821–829. doi.org/10.1053/j.gastro.2016.11.004 · Case-control study (77,046 cases)
- Myint ZW et al. Copper deficiency anemia: review article. Ann Hematol 2018;97:1527–1534. doi.org/10.1007/s00277-018-3407-5 · Review
- Powers HJ. Riboflavin (vitamin B-2) and health. Am J Clin Nutr 2003;77:1352–1360. doi.org/10.1093/ajcn/77.6.1352 · Review (mainly animal and mechanistic data)
- Allen RP et al. Evidence-based and consensus clinical practice guidelines for the iron treatment of restless legs syndrome/Willis-Ekbom disease in adults and children: an IRLSSG task force report. Sleep Med 2018;41:27–44. doi.org/10.1016/j.sleep.2017.11.1126 · Guideline (IRLSSG)
- Winkelman JW et al. Treatment of restless legs syndrome and periodic limb movement disorder: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med 2025;21:137–152. doi.org/10.5664/jcsm.11390 · Guideline (AASM)
