10 min - BioSense Team - 2025-01-09
- level:understanding
- ferritine
- fer
- inflammation
- foie gras
- CRP
- biomarqueurs
- carence martiale
Ferritin is the protein that stores iron: its level, measured by a blood test, reflects your iron stores. A low ferritin generally means reduced iron stores. A high ferritin reflects inflammation, fatty liver or alcohol more often than genuine iron overload, which is why it is read alongside CRP and transferrin saturation.
Ferritin is a very commonly ordered blood test. And yet it is also one of the most poorly understood. Is a low ferritin always serious? Does a high ferritin mean "too much iron"? Why does your doctor sometimes order a transferrin saturation or a CRP at the same time?
Here is what this marker really tells you about your stores, and how to read it in light of your situation.
What is ferritin?
Ferritin is a protein that stores iron in your cells, mainly in the liver, spleen and bone marrow. The blood ferritin level reflects your iron stores: the higher the ferritin, the larger your stores; the lower it is, the more depleted your stores.
Important: ferritin measures neither the iron circulating in your blood (called serum iron) nor the amount of iron actually available to produce red blood cells (assessed with transferrin and its saturation). It assesses the stock, not the flow. This is why a complete iron panel, when it is indicated, includes several tests together.
Another essential point: ferritin is also an "acute-phase" protein. With inflammation, infection, liver damage or certain chronic diseases, it rises independently of iron stores. This is what sometimes makes it tricky to interpret.
Key point - Ferritin reflects your iron stores, but not circulating iron or its availability. It also rises with inflammation, independently of stores. Hence the importance of reading it in context.
Low ferritin: what it can mean
A low ferritin generally reflects a decrease in iron stores. The "normal" range printed by US laboratories varies widely: MedlinePlus lists 13 to 150 ng/mL (13 to 150 µg/L) for women and 30 to 400 ng/mL (30 to 400 µg/L) for men, while the January 2026 ABIM reference ranges list 24 to 307 ng/mL for women and 24 to 336 ng/mL for men (same figures in µg/L). MedlinePlus adds that the lower the level, even within the normal range, the more likely it is that stores are too low.
An important caveat, already raised in our article on reference ranges: a lab's lower limit is not a diagnostic cutoff. And guideline cutoffs differ:
- In the US, the American Society of Hematology (ASH, 2026) suggests diagnosing iron deficiency at a ferritin of 30 ng/mL (30 µg/L) or below in most adults, and up to 50 ng/mL (50 µg/L) in some situations, such as symptoms, heavy periods or pregnancy with anemia. Most of these recommendations are conditional and rest on low- or very low-certainty evidence. They do not mean supplements are automatic.
- Also in the US, the American Gastroenterological Association (2020) uses a ferritin below 45 ng/mL (45 µg/L) in people with anemia.
- In the UK, the British Society of Gastroenterology (2021) notes that a ferritin below 30 µg/L (30 ng/mL) generally reflects low stores and mentions 45 µg/L (45 ng/mL) as a practical compromise.
In other words, a ferritin of 25 ng/mL (25 µg/L) may be displayed as "normal" on the report and yet explain genuine fatigue.
The most common causes of low ferritin
* Losses: heavy periods, chronic digestive bleeding (sometimes silent), repeated blood donations, endurance training (digestive microbleeding and exercise-related hemolysis). * Insufficient intake: restrictive diet, iron-poor diet (particularly in poorly planned vegetarian or vegan diets), malabsorption (celiac disease, chronic gastritis). * Increased needs: pregnancy, breastfeeding, growth in adolescents.
Possible symptoms of low ferritin
Persistent fatigue, breathlessness on exertion, paleness, hair loss, brittle nails, restless legs, concentration problems. These symptoms can appear well before anemia sets in: this is iron deficiency without anemia. This is why low iron stores deserve to be taken seriously even without overt anemia.
Iron deficiency and iron deficiency anemia: not the same thing
Iron deficiency (low iron stores, low ferritin) comes before iron deficiency anemia (low hemoglobin due to lack of iron). Not everyone with iron deficiency is anemic. Often, unexplained fatigue leads to a ferritin test, and the deficiency is managed before it becomes anemia.
Key point - A low ferritin signals a decrease in iron stores. Depending on your context (symptoms, profile, lifestyle), a ferritin between 20 and 50 ng/mL (20 and 50 µg/L) may be too low even if it is displayed as "normal." The conversation with your doctor starts there.
High ferritin: it does not always mean "too much iron"
This is the great nuance of this marker, and the main source of confusion. A high ferritin points to two clinically very different situations.
High ferritin with iron overload: hemochromatosis
The best-known cause is hereditary hemochromatosis, a genetic disorder that causes excessive iron absorption. It then translates into a high ferritin with a high transferrin saturation. More rarely, overload can follow repeated transfusions or certain blood disorders. In these cases, the excess iron can accumulate in the organs and requires specialist care.
High ferritin without iron overload: the most common case
According to the American College of Gastroenterology (2019), fatty liver disease and alcohol-related liver disease are more common than hemochromatosis in people with a high ferritin who do not carry the main at-risk genotypes. Often, a moderately high ferritin is not due to excess iron, but to its rise as an acute-phase protein or to liver cell damage. Several common situations can be responsible:
* Low-grade chronic inflammation (slightly elevated CRP). * Metabolic fatty liver (MASLD, formerly nonalcoholic fatty liver disease), often associated with metabolic syndrome (excess weight, prediabetes, high blood pressure). * Excessive alcohol use, which often raises ferritin and GGT together. * Chronic inflammatory conditions (autoimmune diseases, persistent infections).
This is why a high ferritin should be read alongside CRP, liver enzymes (ALT, AST), GGT, and ideally transferrin saturation. A high ferritin on its own, without context, cannot be acted upon.
Key point - A high ferritin reflects inflammation, fatty liver or alcohol use more often than genuine iron overload. Transferrin saturation and CRP help sort it out.
How to interpret ferritin with the rest of your blood work
You have seen it throughout this article: ferritin is a valuable but ambiguous marker. An identical ferritin can mean radically different things depending on your profile and on the other results of the panel.
Three principles for interpreting it usefully:
* A low ferritin with symptoms (fatigue, breathlessness, hair loss) deserves a discussion even if it sits in the laboratory's "low normal" range. * A high ferritin is not interpreted without CRP, liver enzymes and transferrin saturation. Without them, you risk a misreading. * Your personal context (age, sex, history, treatments, lifestyle, reason for the test) changes the interpretation. That is the whole point of a contextualized reading.
With inflammation, the reading shifts again. ASH considers iron deficiency possible in adults with inflammation (cancer, inflammatory bowel disease, infection) when ferritin is below 100 ng/mL (100 µg/L) or transferrin saturation is below 20%. So a "normal" ferritin does not always rule it out in these situations.
The BioSense method
Ferritin is an excellent example of a biomarker where contextual reading changes everything. BioSense cross-references this result with your health questionnaire (age, sex, menstrual cycles, lifestyle, treatments, reason for the test, any symptoms), with the other iron and inflammation markers when available. Your results are also tracked over time.
*ChatGPT answers you. BioSense knows you.* *BioSense, your prevention companion.* BioSense does not provide a diagnosis and does not replace your doctor. It is a prevention companion that helps you understand, ask the right questions and act day to day.
Ferritin: three questions to ask your doctor
If your ferritin raises questions, low, high, or simply "borderline", here are three questions to prepare for your next visit:
* Given my profile and any symptoms, is my ferritin right for me, or only "within average"? * If it is borderline or abnormal, which additional tests are indicated (transferrin saturation, CRP, liver enzymes, serum iron)? * What change over time should be monitored, and how often?
This preparation steers the visit toward a genuine interpretation, rather than a simple observation about the number.
Frequently asked questions
What ferritin level is considered high?
There is no single cutoff: the range printed on your report remains the reference. In people with the most common genetic form of hemochromatosis (C282Y homozygotes), the 2022 European EASL guidelines suggest iron overload above a ferritin of 200 ng/mL (200 µg/L) in premenopausal women and 300 ng/mL (300 µg/L) in men and postmenopausal women, with a raised transferrin saturation.
Is high iron on a blood test the same as high ferritin?
No: serum iron measures the iron circulating in the blood, whereas ferritin reflects the stock. Serum iron varies a lot from one moment to the next, so it is usually read together with transferrin (or total iron-binding capacity), to calculate transferrin saturation. Your provider may ask you to fast before these tests.
High CRP and high ferritin together: what does it mean?
This combination first suggests inflammation, which raises ferritin independently of iron stores. CRP signals inflammation without giving its cause. Your doctor may suggest a repeat test once the acute episode has passed.
Does high ferritin mean hemochromatosis?
Most often not. Hemochromatosis typically comes with a raised transferrin saturation, which makes it the first test to look at. Looking for a genetic cause is a decision for your doctor.
Import your blood test into BioSense and receive a plain-language reading of your ferritin and all your biomarkers, contextualized to your personal profile and tracked over time. Your data is hosted on servers located in France.
[→ Import my report](/en/onboarding/upload)
Sources and methodology
United States
* Powers JM, Lim MY, Achebe MO, et al. American Society of Hematology 2026 guidelines for diagnosis of iron deficiency. Blood Advances 2026. DOI 10.1182/bloodadvances.2025015950. * American Family Physician. Iron Deficiency Anemia: Guidelines from the American Gastroenterological Association. 2021. Summary of Ko CW, et al. Gastroenterology 2020. DOI 10.1053/j.gastro.2020.06.046. * Kowdley KV, Brown KE, Ahn J, Sundaram V. ACG Clinical Guideline: Hereditary Hemochromatosis. American Journal of Gastroenterology 2019. DOI 10.14309/ajg.0000000000000315. * National Institute of Diabetes and Digestive and Kidney Diseases. Hemochromatosis. * MedlinePlus. Ferritin blood test, January 2026; Ferritin Blood Test. * American Board of Internal Medicine. Laboratory Test Reference Ranges. January 2026.
United Kingdom
* Snook J, Bhala N, Beales ILP, et al. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut 2021;70(11):2030-2051. DOI 10.1136/gutjnl-2021-325210.
Europe
* European Association for the Study of the Liver. EASL Clinical Practice Guidelines on haemochromatosis. Journal of Hepatology 2022;77(2):479-502. DOI 10.1016/j.jhep.2022.03.033. * Rinella ME, Lazarus JV, Ratziu V, et al. A multisociety Delphi consensus statement on new fatty liver disease nomenclature. Journal of Hepatology 2023;79(6):1542-1556. DOI 10.1016/j.jhep.2023.06.003.
*BioSense methodology: our content is based on guidance from US authorities and medical societies (such as the USPSTF, CDC, NIH, FDA, ACC/AHA and ADA), UK bodies (NICE, NHS), European societies and the WHO. Sources are listed by country, and differences between countries are stated when they matter.*
Going further
* Persistent fatigue after 40: which biomarkers to explore first * Blood test reference ranges: why "within range" isn't enough * Why the same blood result doesn't mean the same thing for everyone
*This article is for informational purposes only and is neither medical advice nor a diagnosis. For any questions about your health, consult your doctor. It does not replace a medical visit.*