Ferritin is the storage protein for iron. It reflects the body's iron reserves more accurately than serum iron alone. Ferritin levels track total body iron status: low when iron is depleted, high when iron is abundant.
Ferritin is the most useful single marker for iron status. Low ferritin confirms iron deficiency even before anemia develops, making it the earliest detectable sign. Elevated ferritin can indicate iron overload (hemochromatosis) but also rises with inflammation, liver disease, or excessive alcohol. It's an acute-phase reactant as well as an iron marker. The longevity perspective targets ferritin in the mid-range (50-150 ng/mL in men, 30-100 in women), with both low and high values carrying health implications. Sex-stratified ranges apply strongly. Women typically run much lower due to menstrual iron loss.
Optimal Ferritin: 50-150 ng/mL.
Typically re-tested every 10 weeks.
That double meaning is the whole reason ferritin is interesting. It is one of the few single numbers that can tell you about a nutrient reserve and an inflammatory state at the same time, depending on what surrounds it.
Ferritin is a hollow, shell-shaped protein that holds iron in a stable, non-reactive form inside cells and releases it when the body needs it.
Iron is useful and reactive in equal measure. Your body needs it to build hemoglobin, to run the electron transport chain in mitochondria, and to support enzymes involved in thyroid hormone production and neurotransmitter synthesis. Free iron floating loose in tissue, however, drives oxidative reactions. Ferritin solves that problem by caging thousands of iron atoms inside a protein shell, keeping them inert until they are withdrawn.
Most ferritin sits inside the liver, spleen, bone marrow and macrophages, which are not places a routine blood draw can reach. A small fraction leaks into the bloodstream, and in a person without active inflammation that circulating amount moves in rough proportion to total body iron stores. That is what a ferritin blood test measures, a proxy for the size of the reserve rather than a direct count of it.
The complication is that ferritin is also an acute-phase reactant. During infection, injury, recent surgery or chronic inflammation, the body raises ferritin production as part of its response, partly to withhold iron from pathogens. So the same number that reads as a full tank in one context can read as an inflammatory signal in another. This is why clinicians interpret ferritin with iron, transferrin and saturation values rather than on its own.
Ferritin matters because iron stores empty long before a standard blood count notices, and because iron that accumulates without control is associated with organ damage over years.
On the low side, the sequence is predictable. Stores deplete first, ferritin falls, then iron available for red cell production drops, and only later does hemoglobin fall far enough to register as anemia. Research on iron deficiency anemia describes ferritin as the most useful single marker of depleted stores in the absence of inflammation[1], and clinical reviews treat low ferritin as the earliest reliable signal in the sequence[2]. That gap matters for anyone who feels flat, breathless on stairs or unable to recover from training while being told their blood count is normal.
Iron status also reaches beyond red cells. Studies indicate that low iron stores are associated with restless legs syndrome, and iron status is part of the standard evaluation in that condition[3]. In cardiology, research suggests that iron deficiency defined partly by ferritin is common in people with chronic heart failure and tracks with worse functional capacity, which has prompted work on how best to define the deficiency in that population[4].
On the high side, the concern is cumulative. Persistently raised ferritin with raised transferrin saturation can reflect genuine iron loading, where excess iron deposits in the liver, pancreas, heart and joints over time. Haematology guidance on investigating a raised serum ferritin emphasises distinguishing true iron overload from the far more common reactive elevations caused by inflammation, alcohol, metabolic dysfunction or liver injury[5].
So ferritin is less a pass or fail number and more a dial. Too far in either direction, held there for years, is associated with consequences worth catching early.
A typical lab reference range for ferritin spans a wide band, while FitScript's optimal range is narrower and sits inside it.
| Group | Standard lab reference range | FitScript optimal range |
|---|---|---|
| Adults (general) | 20 to 400 ng/mL | 50 to 150 ng/mL |
| Women | 10 to 200 ng/mL | 30 to 100 ng/mL |
More than 22,000 adult health check-up results from Zhejiang, China were used to set ferritin ranges. Men ran much higher than women, and women's ranges rose with age.[13]
| Sex | Age | Reference range (ng/mL) |
|---|---|---|
| Men | 20 to 92 | 68.8 to 495.5 |
| Women | 20 to 45 | 10.4 to 132.5 |
| Women | 46 to 58 | 13.8 to 241.6 |
| Women | 59 to 90 | 43.7 to 348.8 |
These are the CLSI EP28 (EP28-NP) intervals from the paper: one band for men and three age bands for women. Ferritin results also depend on the assay, so your own lab's printed range is the one to read your result against.
Reference ranges vary by laboratory, assay, age and sex, so always read your result against the range printed on your own report. FitScript's optimal ranges are optimization targets, not diagnostic cut-offs, and a result outside them is not a diagnosis of anything.
The width of the standard range is the point worth sitting with. A ferritin of 22 ng/mL and a ferritin of 380 ng/mL both print as normal, yet they describe very different iron situations. Reviews of iron deficiency note that values in the low end of the reference range can still be consistent with depleted stores, particularly where inflammation is raising ferritin at the same time[2]. The reverse holds too. A single mildly raised value after a recent viral illness often says more about the immune response than about iron.
A high ferritin result means there is more ferritin in circulation than expected, which may reflect iron accumulation, an inflammatory or acute-phase response, liver stress, alcohol intake or metabolic dysfunction.
Related: High Ferritin With Normal Iron? What It Usually Means
What people report. Mildly raised ferritin frequently produces no symptoms at all and is picked up incidentally on routine bloodwork. Where iron loading is established, people describe persistent fatigue, aching joints (often the hands), abdominal discomfort, reduced libido, irregular heartbeat or a bronzed cast to the skin. None of those symptoms is specific, and each has many other explanations.
Common causes. Reactive elevation from infection, recent surgery, injury or chronic inflammatory conditions is the most frequent explanation, because ferritin rises as part of the acute-phase response. Fatty liver and metabolic dysfunction, regular alcohol intake, and other causes of liver inflammation also raise it. Genuine iron overload is less common. Hereditary hemochromatosis, an inherited disorder of iron absorption, leads to iron accumulating in tissue over decades and is a recognised cause of a persistently raised ferritin with a raised transferrin saturation[6]. Iron loading also occurs in people with transfusion-dependent or chronically anemic conditions such as thalassemia, where the balance between iron accumulation and chelation is an active clinical question[7]. Recent iron supplementation or an iron infusion can also lift a result temporarily. Very high values, in the thousands, are sometimes seen in intense inflammatory states such as macrophage activation syndrome[8], and results at that level are worth discussing with a clinician promptly.
Why it matters over time. Where the elevation is reactive, the long-term issue is usually whatever is driving the inflammation rather than the iron itself. Where it reflects true loading, iron deposition in the liver, pancreas, heart and joints is associated with organ injury over years, which is why haematology guidance centres on separating the two early using transferrin saturation, liver markers and clinical context[5]. A high ferritin is a suboptimal finding to investigate, not a verdict, and never one to ignore.
A low ferritin result almost always means iron stores are depleted, because ferritin is rarely low for any reason other than a genuinely empty reserve.
What people report. Tiredness that sleep does not fix, breathlessness or a racing heart during exercise that used to feel easy, cold hands and feet, hair shedding, brittle or spooned nails, headaches, poor concentration, low mood, and sometimes unusual cravings for ice or non-food items. Restless, crawling sensations in the legs at night are also associated with low iron stores and form part of the standard workup in that syndrome[3]. Many people notice declining training performance before they notice anything else.
Common causes. Blood loss is the leading mechanism in adults, whether from heavy menstrual bleeding or from slow gastrointestinal losses. Intake can be the issue in diets low in bioavailable iron, and absorption can be the issue in people with celiac disease, prior gastric surgery, chronic gastritis or long-term acid suppression. Demand rises in pregnancy, in rapid growth, and in high-volume endurance training. Frequent blood donation draws the reserve down steadily. Clinical reviews stress that in adults, and particularly in older adults, unexplained iron deficiency warrants a search for a source of blood loss rather than supplementation alone[9], a point long-standing primary care guidance has made as well[10].
Why it matters over time. Left unaddressed, depleted stores progress toward iron deficiency anemia, with reduced oxygen-carrying capacity and the functional consequences that follow[1]. In people with chronic heart failure, iron deficiency is associated with worse symptoms and exercise capacity, and intravenous iron has been studied in that setting with reported improvements in symptoms and function[11]. Repletion strategies vary, and research continues to examine which oral supplementation regimens work best and for how long[12]. What form of repletion is appropriate, if any, is a decision for a licensed provider who has seen your full picture, since iron given to the wrong person can push stores in the wrong direction.
Several everyday factors move ferritin independently of your true iron reserve, which is why timing and context matter when a sample is taken.
Acute illness is the biggest one. An infection, a recent vaccination, a fresh injury or surgery can raise ferritin for days to weeks through the acute-phase response, which may mask a genuinely low reserve. A very hard training session or a marathon can produce a short-lived rise through a similar mechanism. Where the result looks odd, repeating it once the acute event has passed is usually more informative than acting on the first value.
Recent iron intake matters too. Supplements taken shortly before a draw, and especially a recent intravenous iron infusion, can lift ferritin well above baseline for a period. Regular alcohol intake and liver inflammation push it up. Significant weight change and metabolic status can shift it in either direction. Menstrual timing and recent blood donation shift it down.
Laboratory factors are real as well. Different analysers and assays produce slightly different numbers, so tracking a trend at one lab is more reliable than comparing single values across providers. Fasting is not strictly required for ferritin, but keeping the conditions consistent (same lab, similar time of day, similar state) makes a trend readable.
Among medications, long-term acid-suppressing drugs may reduce dietary iron absorption, and drugs that increase the chance of gastrointestinal bleeding may deplete stores over time. These are general associations rather than certainties for any individual, and any change to prescribed medication is a conversation with the prescriber, not a self-directed experiment. This page stays at the level of interpretation. The practical question of how to raise or lower a result is covered in depth in FitScript's dedicated iron-status guide.
Ferritin is measured as part of an iron panel, drawn alongside serum iron, total iron-binding capacity and transferrin saturation, because those four values only make sense together.
Within a FitScript membership, ferritin sits inside a broader program of 150+ biomarkers tested per year, so the result is read against inflammatory markers, a full blood count and nutrient status from the same draw rather than in isolation. Repeat testing across the year is what turns a single number into a trend, and a trend is what distinguishes a transient inflammatory bump from a reserve that is steadily emptying.
Atlas, the AI health advisor, interprets the result in the context of your other markers, your symptoms and your history, and writes that interpretation into your FitScript. Where a result suggests a pattern worth acting on, any prescription therapy or infusion is evaluated and decided by a licensed provider who reviews the member first. No lab value on its own determines a treatment.
This article is educational and is not medical advice. Discuss your own results and any treatment with a clinician or licensed provider before acting on them.
Ferritin answers how much iron is stored. The markers around it answer how much is circulating, how hard the body is working to carry it, and whether red cell production is affected yet.
Serum Iron shows the iron currently in transit, a value that swings with recent meals and time of day. TIBC reflects how much carrying capacity is available and typically rises as stores fall. Iron Saturation combines the two and is the key value for separating reactive ferritin elevations from genuine iron loading. Hemoglobin shows whether oxygen-carrying capacity has been affected, and MCV describes red cell size, which tends to fall as iron deficiency progresses. Vitamin D (25-OH) is worth seeing alongside these because fatigue rarely has a single nutrient explanation. Testing these together, as in a Longevity Nutrients panel, gives a far more interpretable picture than ferritin alone.
Ferritin is your iron savings account, reported as a blood value. Low usually means the account is drawn down and the reason deserves investigation, particularly in adults where blood loss is the common mechanism. High means something is adding to the signal, most often inflammation, alcohol or liver and metabolic stress, and less often genuine iron accumulation. Neither result is a diagnosis, and both are read against saturation, blood count and inflammatory markers before anything is concluded. The most useful habit is simple, test consistently, look at the trend, and take an out-of-range value to a clinician rather than to a search bar.
It measures the amount of the iron-storage protein ferritin circulating in your blood, which acts as a proxy for how much iron your body has in reserve. It does not measure the iron in your red blood cells directly, which is why it is read alongside serum iron, TIBC, iron saturation and hemoglobin.
A typical lab reference range runs from roughly 20 to 400 ng/mL, though ranges vary by laboratory, assay, age and sex. FitScript's optimal range is narrower, 50 to 150 ng/mL for adults generally and 30 to 100 ng/mL for women. Optimal ranges are optimization targets rather than diagnostic cut-offs.
Yes. Because ferritin rises with inflammation, infection or recent injury, a value sitting in the lower part of the reference range can coexist with depleted stores. Clinical reviews note this overlap, which is why iron saturation, TIBC and inflammatory markers are checked at the same time rather than relying on ferritin alone.
The most common cause is a reactive rise from inflammation, infection, recent surgery or injury. Alcohol intake, fatty liver, other liver inflammation and metabolic dysfunction also raise it. Genuine iron overload, including hereditary hemochromatosis and transfusion-related loading, is a less frequent but important cause that iron saturation helps identify.
A single mildly raised value is often a suboptimal finding with a benign explanation, such as a recent illness. It still deserves follow-up rather than dismissal, because persistent elevation with raised transferrin saturation can reflect iron accumulation. Very high values are worth discussing with a clinician promptly.
Commonly reported symptoms include fatigue that rest does not resolve, breathlessness or a racing heart with exertion, cold extremities, hair shedding, brittle nails, headaches, poor concentration and restless sensations in the legs at night. None of these confirms iron deficiency on its own, since each has several possible explanations.
Fasting is not strictly required for ferritin, but consistency helps. Using the same laboratory, a similar time of day and a similar state each time makes a trend readable. It is also worth avoiding testing during an acute illness or within days of hard exercise or a recent iron infusion.
Retesting frequency depends on why it was checked and what the result showed, and is a decision for the clinician reviewing your case. A trend across repeated draws over a year is far more informative than a single value, because it separates a transient inflammatory bump from a reserve that is steadily changing.
That is a decision for a licensed provider rather than a self-directed one. Low ferritin in an adult often means the underlying cause, frequently blood loss, needs identifying first, and iron taken by someone who does not need it can push stores the wrong way. Bring the result to a clinician for evaluation.