How to Increase Ferritin Levels: What the Evidence Says About Iron Dosing, Food and Timing

Key Takeaways: How to Increase Ferritin Levels

• Confirm the deficiency first. The American Society of Hematology (ASH) 2026 guideline uses a ferritin threshold of 30 ng/mL (30 µg/L) or lower for adults, including menstruating and pregnant individuals, and 50 ng/mL or lower for selected high-risk groups; different criteria apply when inflammation is present.[1]
• Find the cause. The authors of one trial observed that iron-deficiency anemia relapsed easily when causes such as bleeding or impaired absorption were not investigated and addressed.[2]
• More iron per dose is not proportionally better. A sixfold increase in the oral dose produced only about a threefold increase in iron absorbed.[3]
• Alternate-day dosing may absorb better and be easier to tolerate. In women with iron-deficiency anemia, fractional absorption was 40–50% higher when the dose followed a day without iron.[4] In a later 6-month trial in iron-depleted women given the same total iron dose, ferritin was similar with alternate-day and daily dosing, but gastrointestinal side effects were less common with alternate-day dosing.[5]
• Vitamin C tablets did not improve the response to oral iron in a 440-patient randomized trial in iron-deficiency anemia.[2]
• Give it time and retest. Ferritin response is measured over weeks, not days; in the athlete trials reviewed, protocols shorter than about 6 weeks were ineffective.[6]
• Iron is a treatment for deficiency, not a booster. In athletes, oral iron raised ferritin mainly when it started very low.[6]
• Ferritin rarely explains fatigue on its own. In my clinical experience, fatigue is usually multifactorial, and a low ferritin seldom explains it by itself, especially when hemoglobin is normal.
• But a low ferritin should not be dismissed. In one randomized trial, oral iron reduced fatigue more than placebo in non-anemic women with unexplained fatigue and ferritin below 50 µg/L.[7]
• Athletes may need a higher target. A Swiss sports medicine consensus considers 30 µg/L an appropriate ferritin cut-off for athletes,[8] and in my practice I aim for above 30 µg/L, preferably above 40 µg/L, even without anemia.
• Restless legs call for a higher target. The Finnish Current Care guideline recommends a ferritin target of at least 75–100 µg/L in restless legs syndrome.[9]
• Heme iron from meat is absorbed better than non-heme iron (about 5–35% vs. about 2–20%),[10] which is why I often recommend red meat to patients with iron deficiency when it suits them.
• IV iron is not a performance treatment. In my view, the indications for athletes are the same as for anyone else.

Introduction: How to Increase Ferritin Levels Without Guesswork

The question of how to increase ferritin levels sounds simple — take iron — but the details decide whether supplementation works: whether the deficiency is real, what caused it, how much iron is taken, how often, at what time of day and for how long.

Ferritin is the body’s iron-storage protein, and the blood test is an indirect marker of iron stores (see What Is Ferritin? for the basics). This article focuses on the practical side: how to increase ferritin levels with food and oral iron, what recent research says about dosing schedules, how quickly ferritin can be expected to rise, what is different for athletes, and when oral iron is not enough.

Ferritin is one of the more commonly requested tests in everyday practice. In my clinical experience, many patients ask for it themselves and are worried about their own ferritin level, most often because of tiredness and exhaustion, and sometimes because of symptoms such as restless legs. Ferritin has also become something of a fashionable explanation for exhaustion, and I am careful not to draw causal conclusions too far from a low value. Fatigue is usually multifactorial, and in many patients psychosocial load is a major contributor that deserves attention in its own right. Even so, a careful differential diagnosis is needed, somatic causes are worth excluding at least once, and ferritin is usually the first test patients ask about. I often tell them that a ferritin value rarely explains fatigue on its own, especially when they are not anemic.

This clinical caution has to be weighed against trial evidence. In a randomized trial of 198 non-anemic menstruating women with unexplained fatigue and ferritin below 50 µg/L, fatigue scores fell by 47.7% after 12 weeks of oral iron and by 28.8% with placebo (P = .02).[7] Fatigue is a subjective outcome and the trial was sponsored by an iron-supplement manufacturer, and there was no significant difference in quality of life, depression or anxiety, but the result means that a low ferritin should not be dismissed either.

Step 1: Confirm That Your Ferritin Is Actually Low

Before working out how to increase ferritin levels, it is worth confirming that they need increasing. Laboratory reference ranges for ferritin vary, and a value within a laboratory’s range may still fall at or below the thresholds now recommended for diagnosis.[1]

In 2026, ASH published a guideline on diagnosing iron deficiency.[1] It recommends a serum ferritin threshold of 30 ng/mL or lower, rather than 15 ng/mL, for adults, including menstruating and pregnant individuals. A higher threshold of 50 ng/mL or lower may be appropriate for high-risk groups, such as people with heavy menstrual bleeding and pregnant individuals with anemia. For adults with inflammation, iron deficiency may be considered when ferritin is below 100 ng/mL or transferrin saturation is below 20%.[1] The guideline addresses diagnosis rather than treatment.[1]

The inflammation caveat matters. A Cochrane diagnostic review notes that ferritin is an acute-phase protein that rises in inflammation and infection. At a threshold of 30 µg/L, it found low-certainty evidence that ferritin is reasonably sensitive and very specific for iron deficiency in people presenting for medical care, but insufficient evidence on how well it performs when screening people without symptoms.[11] This is one reason ferritin is usually read together with a full blood count, transferrin saturation and an inflammatory marker such as CRP (see Iron Panel Interpretation for Athletes).

In practice, ferritin is rarely enough on its own. Hemoglobin is the first test I look at alongside ferritin, and I usually check thyroid function tests as well. If anemia is found, it is usually worth extending the work-up, for example with vitamin B12 and folate, and other iron values such as serum iron, transferrin and transferrin saturation may also be checked.

Many of the patients I see are not anemic, and their ferritin is not outside the laboratory reference range but sits in its lowest quarter. In other words, I often see what may be iron deficiency without anemia. This is the group in which the newer, higher diagnostic thresholds matter most, because a ferritin value that a laboratory reports as normal can still fall at or below them.

Step 2: Find Out Why Ferritin Fell

Raising ferritin without knowing why it fell treats the number, not the problem. In the 440-patient vitamin C trial discussed below, the most common cause of iron-deficiency anemia in women was heavy menstrual bleeding due to uterine fibroids or endometriosis, found in 389 women (91.3%).[2] The authors also observed that iron-deficiency anemia relapsed easily when underlying causes such as bleeding or impaired absorption were not investigated and addressed.[2]

The American Gastroenterological Association (AGA) guideline on iron-deficiency anemia recommends bidirectional endoscopy for asymptomatic men and postmenopausal women with iron-deficiency anemia, and states that celiac disease must be considered in the differential diagnosis, even in patients without symptoms.[12] In patients with anemia, it also recommends a ferritin cut-off of 45 ng/mL rather than 15 ng/mL for diagnosing iron deficiency, which raised sensitivity to 85% at a specificity of 92%.[12]

In iron-deficiency anemia, oral iron is the first-line treatment, but the cause of the iron deficiency usually needs to be investigated as well. In women, my first question is often whether their menstrual periods are heavy, which in my clinical experience is a fairly common cause of anemia. Some patients may instead have gastrointestinal bleeding that can go unnoticed. It can sometimes cause anemia quite rapidly, and these patients may have dark stools. There are other causes too, such as chronic undernutrition, and in vegetarians iron may be absorbed less well.

How to Increase Ferritin Levels With Food

Iron absorption from food depends on both the diet and the person. A review by Hurrell and Egli estimated dietary iron bioavailability at 14–18% for mixed diets and 5–12% for vegetarian diets in people with no iron stores.[13] The same review notes that enhancers and inhibitors such as phytate, polyphenols, calcium, ascorbic acid and muscle tissue have repeatedly been shown to affect absorption in single-meal studies, whereas their effect is more modest across a varied multi-meal diet, and that a person’s iron status generally has a greater effect on absorption than diet composition.[13]

Practical points supported by the literature:

• Ascorbic acid and meat, fish and poultry enhance iron absorption; polyphenols and phytates (in tea, coffee and vegetables) and calcium inhibit it.[14]
• Separate tea from iron-containing meals. For people at risk, one review recommends drinking tea between meals rather than with them.[14] In a stable-isotope trial in iron-replete, non-anemic women, non-heme iron absorption from a porridge meal was 5.7% with water, 3.6% with tea taken at the same time, and 5.7% when tea was taken 1 hour after the meal; the 1-hour gap roughly halved tea’s inhibitory effect, from 37.2% to 18.1%.[15]

In athletes, iron deficiency is initially treated with a nutritional intervention, and oral iron supplementation can be used if a negative iron balance persists.[6]

In my clinical practice, I often recommend red meat to patients with iron deficiency, taking into account other factors such as high cholesterol. Heme iron is the form absorbed best: a narrative review on iron in athletes describes heme iron sources (from meat) as having greater absorptive capacity, about 5–35%, than non-heme sources, about 2–20%.[10]

How to Increase Ferritin Levels With Iron Supplements: Dose and Schedule

When iron values are low, with or without anemia, patients can take oral iron, and in my clinical experience many of them feel that it helps. I cannot say how much of that is a placebo effect. In my view, the benefit of raising ferritin is less clear in people who do not exercise, but many patients believe in it and want to take iron, and in that situation I do not discourage it. Athletes are a different case, as discussed below.

Restless legs syndrome is a situation in which the ferritin target is higher. In my clinical practice, I usually recommend that patients with restless legs keep their ferritin closer to the upper third of the reference range, and Finnish guidance points in the same direction: the Finnish Current Care (Käypä hoito) guideline on restless legs and sleep recommends considering iron supplementation for all patients whose ferritin is below 75 µg/L or whose transferrin saturation is below 20%, with a ferritin target of at least 75–100 µg/L.[9] In these patients, iron supplementation is, in my view, more clearly indicated.

Why more iron per dose is not proportionally better

Oral iron triggers a rise in hepcidin, the hormone that limits iron absorption from the gut (covered in more detail in Hepcidin and Iron Absorption in Athletes).[3] In a stable-isotope study of 54 non-anemic young women with ferritin of 20 µg/L or lower, serum hepcidin was raised 24 hours after doses of 60 mg or more, and fractional iron absorption from the next dose fell by 35% to 45%.[3] A sixfold increase in dose (40 to 240 mg) produced only a threefold increase in iron absorbed (6.7 to 18.1 mg), and adding an afternoon dose to two morning doses did not significantly increase total absorption.[3] The authors concluded that lower doses (40–80 mg) and avoiding twice-daily dosing maximise fractional absorption, and that the duration of the hepcidin response supports alternate-day dosing, while the longer-term effects of such schedules need further study.[3]

Alternate-day dosing

The same research group then tested this in 19 women with iron-deficiency anemia, given 100 mg or 200 mg of ferrous sulfate at 8 AM.[4] For both doses, fractional absorption was 40–50% higher on the days that followed a day without iron than on the day that immediately followed a previous dose. Total absorption from a single 200 mg dose on alternate days was approximately twice that from 100 mg on consecutive days.[4] The authors noted that these were short-term absorption measurements and that the potential benefits still need confirming in longer trials with clinical outcomes such as hemoglobin, iron status and side effects.[4]

A longer randomized, double-blind trial has since compared the two schedules in 150 iron-depleted young women (ferritin ≤30 µg/L) given the same total amount of iron: 100 mg daily for 3 months followed by placebo for 3 months, or 100 mg on alternate days for 6 months.[5] At the same cumulative dose, median ferritin did not differ (43.8 µg/L with daily and 44.8 µg/L with alternate-day dosing; P = .98), although the treatment durations differed. Gastrointestinal side effects were less common with alternate-day dosing, and at 6 months iron deficiency was less prevalent in the alternate-day group (3.0% vs. 11.4%; P = .049).[5] A 2025 meta-analysis of 11 randomized trials (1,014 participants) likewise found no significant difference in ferritin between daily and alternate-day dosing, with similar overall adverse event rates, although the certainty of evidence was very low for most outcomes.[16]

In practice, a single dose taken every other day may be a reasonable way to increase ferritin levels, particularly for people who tolerate daily iron poorly. Alternate-day dosing may improve tolerability without necessarily producing a greater ferritin response than daily dosing.

Side effects and adherence

Gastrointestinal side effects are a common practical problem with oral iron. A meta-analysis of 43 randomized trials (6,831 adults) found that ferrous sulfate increased the odds of gastrointestinal side effects compared with placebo (OR 2.32) and with intravenous iron (OR 3.05), with no significant relationship to dose.[17] Pooled incidences in the ferrous sulfate groups were 12% for constipation, 11% for nausea and 8% for diarrhea, and modified-release ferrous sulfate did not appear to cause fewer side effects.[17] Citing earlier studies, the authors note that these side effects lead to non-adherence in up to 50% of patients.[17]

Do You Need to Take Vitamin C With Iron Tablets?

Vitamin C is often taken routinely with oral iron, although whether it is needed has been uncertain.[2] A randomized equivalence trial tested it directly in 440 adults with newly diagnosed iron-deficiency anemia (96.8% women).[2] Participants took a 100 mg iron tablet every 8 hours for 3 months, with or without 200 mg of vitamin C. After 2 weeks, hemoglobin had risen by 2.00 g/dL with vitamin C and 1.84 g/dL without it, which met the criteria for equivalence. At 8 weeks, ferritin had risen by 35.75 ng/mL and 34.48 ng/mL, respectively, a non-significant difference (P = .21), and adverse event rates were similar.[2] The authors concluded that vitamin C supplements are not essential for patients with iron-deficiency anemia taking oral iron.[2]

This was a single-centre, open-label trial in China with three daily doses, so it does not test vitamin C alongside alternate-day dosing. Ascorbic acid remains a recognised dietary enhancer of iron absorption,[14] but, based on this trial, adding a vitamin C tablet to an iron supplement does not appear necessary for most adults with iron-deficiency anemia (see also Vitamin C in Athletes).

How Fast Do Ferritin Levels Rise?

Randomized trials suggest that the rise is gradual.

• In 198 non-anemic menstruating women with fatigue and ferritin below 50 µg/L, 80 mg of elemental iron daily raised ferritin by 6.8 µg/L more than placebo at 6 weeks and by 11.4 µg/L more at 12 weeks.[7] The authors suggested checking blood markers after 6 weeks of treatment. The trial was sponsored by an iron-supplement manufacturer.[7]
• In the vitamin C trial, in which patients had iron-deficiency anemia and very low baseline ferritin (around 6 ng/mL), ferritin rose by roughly 35 ng/mL over 8 weeks with a 100 mg iron tablet taken three times daily.[2]
• In athletes, a 2024 meta-analysis of 13 randomized trials (449 participants) found that doses of 16–100 mg of elemental iron daily improved hematological markers over 6–8 weeks, while shorter protocols were ineffective. Even after supplementation, ferritin remained below 35 µg/L in 10 of the 13 studies.[6]

The practical message: plan for a course lasting several weeks to a few months, then retest under standardized conditions (see Preparing for a Blood Test as an Athlete), rather than judging success after a week or two.

How to Increase Ferritin Levels in Athletes

Athletes face an extra obstacle: exercise itself raises hepcidin. An individual participant data meta-analysis notes that hepcidin has been shown to peak 3–6 hours after exercise, and found that exercise is associated with a 1.5–2.5-fold increase in hepcidin concentrations.[18]

Timing around training may therefore matter. In a crossover study of 16 endurance-trained runners with ferritin below 50 µg/L, an iron-fortified drink was given with a standardized meal 30 minutes after a 90-minute run performed either in the morning or in the afternoon.[19] Fractional iron absorption was significantly greater at breakfast after the morning run than in the rested condition and than at dinner on the same day, despite exercise raising IL-6 and hepcidin.[19] This was a small study using an iron-fortified drink rather than tablets, but it is consistent with taking iron in the morning, shortly after a morning session, rather than in the evening.

Correcting a true deficiency can matter for performance. A systematic review of 23 studies (669 high-level female athletes across 16 sports) defined iron deficiency as ferritin below 40 µg/L and reported that it reduced endurance performance by 3%–4%; endurance performance improved by 2%–20% with 100 mg of elemental iron per day orally for up to 56 days, or with parenteral iron given bi-daily over 8–10 days.[20] A meta-analysis in iron-deficient, non-anemic endurance athletes, which pooled different routes of iron administration, found a large effect of iron treatment on ferritin (Hedges’ g = 1.088) and a moderate effect on VO₂max (g = 0.610), and noted that treatments lasting beyond 80 days appeared to have the least effect on ferritin.[21]

The other side of the evidence is equally important. In the 2024 athlete meta-analysis, oral iron clearly raised ferritin in participants who started at 12 µg/L or lower, but had minimal, if any, effect in those with higher starting values.[6] Athlete-specific ferritin targets are discussed in Ferritin Levels for Athletes.

For athletes, the picture is different. In my clinical experience, athletes with clearly low ferritin may benefit from raising it with oral iron, because their performance may already decline at levels that might cause no symptoms in a sedentary person. A Swiss sports medicine consensus describes ferritin of 15–30 µg/L as low iron stores in athletes over 15 years and considers 30 µg/L an appropriate cut-off,[8] and the systematic review above defined iron deficiency in high-level female athletes as ferritin below 40 µg/L.[20] In practice, I usually recommend that athletes take oral iron to bring ferritin above 30 µg/L, and preferably above 40 µg/L, even when they are not anemic.

When Oral Iron Is Not Enough

Intravenous iron is not absorbed through the gut, and in randomized trials ferrous sulfate caused more gastrointestinal side effects than intravenous iron.[17] In 15 national- and international-level runners with iron deficiency without anemia, a single 500 mg intravenous iron injection improved iron status for at least 4 weeks compared with placebo, but did not improve aerobic capacity.[22] The authors of the 2024 athlete meta-analysis suggested that, because oral iron often left ferritin below 35 µg/L, an earlier pathway to intravenous iron could be considered for some athletes.[6]

Intravenous iron still requires a medical indication. Athletes subject to anti-doping rules should also note that the 2026 Prohibited List bans intravenous infusions or injections of more than 100 mL per 12-hour period, except those legitimately received in the course of hospital treatments, surgical procedures or clinical diagnostic investigations.[23] See IV Iron for Athletes for indications and practical considerations.

Many patients ask about intravenous iron. In Finland, the criteria for it are fairly strict, at least in public health care. On the hematology course during my medical studies, low iron values without anemia were viewed with some reservation, and the message was that patients without anemia were not to be referred for iron infusions. In the private sector, IV iron may be given more readily. The Finnish Current Care (Käypä hoito) guideline on heavy menstrual bleeding states that parenteral iron may be needed if oral iron is not sufficient or causes significant adverse effects.[24] In my view, IV iron is not a performance treatment for athletes: the indications are the same as for sedentary patients.

What Not to Do

• Do not take iron “just in case.” Iron supplementation should be guided by evidence of iron deficiency and clinical need. In one athlete meta-analysis, the ferritin response was greatest in participants starting at 12 µg/L or lower, with minimal, if any, effect at higher starting values.[6]
• Do not split one dose into several daily doses expecting faster results. An extra afternoon dose did not significantly increase total absorption.[3]
• Do not judge the result too early. The authors of one trial suggested assessing the effect with blood markers after six weeks of treatment.[7]
• Do not ignore the cause. The authors of one trial observed that iron-deficiency anemia relapsed easily when bleeding or impaired absorption was not investigated and addressed.[2]

Conclusion: How to Increase Ferritin Levels Effectively

The evidence on how to increase ferritin levels points to a few clear principles. Confirm the deficiency against current thresholds — ASH now uses 30 ng/mL or lower for most adults[1] — and look for the cause. Use food sensibly, keeping tea away from iron-rich meals.[15] For supplements, larger and more frequent doses yield diminishing returns, because a sixfold increase in dose produced only a threefold increase in absorbed iron,[3] and alternate-day dosing may improve absorption and tolerability,[4] although one randomized trial found no significant difference in ferritin at equal cumulative iron doses,[5] and a subsequent meta-analysis also found no statistically significant overall ferritin difference.[16] Vitamin C tablets do not appear necessary.[2] Expect change over weeks to months and retest. For athletes, morning iron after a morning session may absorb better,[19] correcting a real deficiency can improve endurance performance,[20] and oral iron raised ferritin little when baseline ferritin was not very low.[6]

From a clinical perspective, ferritin is a useful test but rarely the whole story. In my experience, fatigue is usually multifactorial, and a low ferritin, especially without anemia, seldom explains it on its own, so the differential diagnosis deserves as much attention as the iron level itself. When iron deficiency is confirmed, oral iron is the first-line treatment, alongside dietary advice that in my practice often includes red meat. For athletes, I aim for a ferritin above 30 µg/L and preferably above 40 µg/L, and for patients with restless legs the target is higher still. Intravenous iron, in my view, has the same indications for athletes as for everyone else.

References

1. https://doi.org/10.1182/bloodadvances.2025015950
2. https://doi.org/10.1001/jamanetworkopen.2020.23644
3. https://doi.org/10.1182/blood-2015-05-642223
4. https://doi.org/10.3324/haematol.2019.220830
5. https://doi.org/10.1016/j.eclinm.2023.102286
6. https://doi.org/10.1007/s40279-024-01992-8
7. https://doi.org/10.1503/cmaj.110950
8. https://doi.org/10.4414/smw.2015.14196
9. https://www.kaypahoito.fi/nix03635
10. https://doi.org/10.1007/s00421-019-04157-y
11. https://doi.org/10.1002/14651858.CD011817.pub2
12. https://doi.org/10.1053/j.gastro.2020.06.046
13. https://doi.org/10.3945/ajcn.2010.28674F
14. https://doi.org/10.1080/10408690091189194
15. https://doi.org/10.3945/ajcn.117.161364
16. https://doi.org/10.1186/s40360-025-00984-2
17. https://doi.org/10.1371/journal.pone.0117383
18. https://doi.org/10.1007/s40279-023-01874-5
19. https://doi.org/10.1249/MSS.0000000000002026
20. https://doi.org/10.1016/j.jshs.2024.101009
21. https://doi.org/10.1136/bjsports-2014-093624
22. https://doi.org/10.1249/MSS.0000000000000568
23. https://kamu.suek.fi/en/dopingsubstances/
24. https://www.kaypahoito.fi/hoi50033

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