How to prepare for the 'Ferritin' test: rules for taking it

Ferritin is a protein in which the body stores iron. Its level in the blood is considered the best simple marker of iron stores, and it is where the search for a deficiency begins — a deficiency that often occurs in athletes, especially in runners, women and vegetarians. However, ferritin has an insidious property: it rises during inflammation. The editorial team explains how to take the test to get a result you can trust.

What ferritin shows

Most ferritin is located inside the cells of the liver, spleen and bone marrow, where it stores iron in a non-toxic form. A small amount of ferritin circulates in the blood, and its concentration in a healthy person is proportional to the body's iron stores.

When the stores are depleted, ferritin decreases before hemoglobin does. Therefore it makes it possible to detect latent iron deficiency even before anemia develops. For an athlete this is important: even without anemia, iron deficiency can reduce endurance, worsen recovery and increase fatigue.

At the same time, ferritin is an acute-phase protein. During infection, inflammation, tissue damage and liver diseases, its level rises regardless of iron stores. In such a situation, «normal» ferritin may mask a real deficiency.

That is precisely why the WHO in its 2020 guideline proposes different thresholds for healthy people and for people with inflammation. Proper preparation for the test comes down to minimizing the effect of inflammation and getting a value that reflects the true stores.

Inflammation and training: the main traps

Any acute infection — a cold, flu, intestinal infection — as well as an exacerbation of chronic inflammatory diseases raises ferritin. A routine test should be postponed for at least 2–4 weeks after recovery so that the level returns to baseline.

For athletes, a specific trap is intense and prolonged exertion. An exhausting workout, a marathon, a multi-day competition cause muscle damage and an inflammatory reaction. During this period inflammatory cytokines rise, in particular interleukin-6, and after them — hepcidin and ferritin.

Studies by Peeling's group have shown that hepcidin rises a few hours after intense running, temporarily blocking iron absorption. This explains why athletes are advised to take iron not immediately after a hard workout, and in tests — to avoid drawing blood after competitions.

The editorial team's practical rule: take ferritin after 1–2 days of rest or light training, no earlier than a few days after a competition, marathon or a training camp with heavy loads. This way you will get a value that is not inflated by an inflammatory reaction.

Iron preparations, food and alcohol

Oral iron preparations most affect the level of serum iron, which rises within a few hours of taking them. Ferritin changes more slowly, but in order not to distort the entire iron metabolism panel, laboratories usually advise not taking iron for at least 24 hours before the test.

Intravenous iron administration sharply raises ferritin, and this effect lasts for weeks. To assess real stores after an infusion, the test is usually repeated no earlier than 4–8 weeks later — the specific timing is determined by the doctor.

Alcohol and liver diseases raise ferritin even without excess iron. Regular alcohol consumption, non-alcoholic fatty liver disease, metabolic syndrome are common causes of moderately elevated ferritin. Abstain from alcohol for at least 2–3 days before the test.

Ferritin itself depends little on a single meal. However, if it is taken together with serum iron and transferrin, it is worth coming in the morning while fasting: the iron level in the blood has a daily rhythm and reacts to food.

• iron preparations — a pause of at least 24 hours (in agreement with the doctor);
• after intravenous iron — a test no earlier than a few weeks later;
• alcohol — abstain for 2–3 days;
• for the iron panel — morning, fasting.

Rules for taking it and what to test together

Ferritin on its own is informative, but for a reliable conclusion it is better to supplement it with other indicators. The most useful combination is ferritin together with an inflammation marker and a complete blood count.

If CRP is elevated, ferritin is interpreted with caution: a normal value does not rule out deficiency. In such cases transferrin saturation is especially valuable — it decreases in iron deficiency.

For tracking trends, take the test under similar conditions: at the same time of day, in an analogous period of the training cycle, at one laboratory. Comparing a value after rest with a value after a competition is incorrect.

Women should take the menstrual cycle into account: large blood losses gradually deplete iron stores, so regular ferritin monitoring is especially useful for them.

How to interpret the result

According to the 2020 WHO guideline, in practically healthy adults ferritin below 15 µg/L indicates depletion of iron stores. In the presence of infection or inflammation, a significantly higher level is considered the deficiency threshold — about 70 µg/L.

In sports medicine, broader thresholds are often used, since symptoms of deficiency can appear at higher values. Many reviews for athletes mention a level of about 30–35 µg/L as the boundary beyond which it is worth working on replenishing stores, but the final decision is always individual.

High ferritin does not always mean iron excess. Most often it is inflammation, alcohol, fatty liver disease or metabolic syndrome. To rule out hereditary hemochromatosis, the doctor assesses transferrin saturation and, if necessary, orders a genetic test.

You should not take iron preparations on your own based only on a «low-normal» value — an excess of iron is harmful. The decision on taking it, the dosage and the duration should be made by a doctor.

Editorial conclusions

Ferritin reflects iron stores well, but is inflated during inflammation, infection, after exhausting exertion, with alcohol consumption and liver diseases.

For a reliable result, take the test after rest, without iron preparations the day before, without alcohol for a few days and together with C-reactive protein and a complete blood count.

Athletes should monitor ferritin regularly, in a similar phase of the training cycle, in order to see the real trend.

We also recommend reading our materials on glycated hemoglobin, on creatine phosphokinase as a marker of muscle damage, and on cortisol.

References

1. World Health Organization. WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations. Geneva: WHO; 2020.
2. Camaschella C. Iron-deficiency anemia. N Engl J Med. 2015;372(19):1832–1843.
3. Pasricha SR, Tye-Din J, Muckenthaler MU, Swinkels DW. Iron deficiency. Lancet. 2021;397(10270):233–248.
4. Peeling P, Dawson B, Goodman C, et al. Athletic induced iron deficiency: new insights into the role of inflammation, cytokines and hormones. Eur J Appl Physiol. 2008;103(4):381–391.
5. Sim M, Garvican-Lewis LA, Cox GR, et al. Iron considerations for the athlete: a narrative review. Eur J Appl Physiol. 2019;119(7):1463–1478.