Optimal ferritin levels, from deficiency to overload

Ferritin is an iron-storage protein present in all cells. A small amount circulates in the blood, and the ferritin test measures it in serum or plasma. In its 2020 guideline, the World Health Organization (WHO) states that in the absence of inflammation, plasma or serum ferritin is positively correlated with the size of total body iron stores: low in iron-deficient people and high in iron-loaded ones.

That condition, in the absence of inflammation, is the key to reading ferritin levels. WHO also notes that inflammation raises ferritin, so a result can go up for reasons that have nothing to do with iron stores.

WHO recommends ferritin as a good marker of iron stores and as the test to diagnose iron deficiency in otherwise apparently healthy people. Its cutoffs depend on age and on whether infection or inflammation is present.

The difference between 15 and 45 is not a contradiction. WHO sets cutoffs for individuals and populations in general, while the American Gastroenterological Association (AGA) guideline addresses patients who already have anemia, where it recommends the higher cutoff when using ferritin to diagnose iron deficiency. The AGA adds that in inflammatory conditions or chronic kidney disease, tests such as CRP or transferrin saturation may be needed alongside ferritin.

At the other end, WHO gives thresholds that may indicate a risk of iron overload. In otherwise healthy people, that is ferritin above 150 µg/L in menstruating women and above 200 µg/L in men and non-menstruating women. In adults who are not healthy, WHO uses above 500 µg/L.

Because inflammation raises ferritin, it can hide iron deficiency behind a normal-looking number. WHO's answer is to measure inflammation at the same time. In areas of widespread infection or inflammation, it recommends assessing ferritin together with two acute-phase proteins, CRP and alpha-1-acid glycoprotein (AGP).

WHO describes several ways to account for inflammation: raising the deficiency cutoff (to 70 µg/L in adults), excluding results with raised CRP or AGP from population estimates, or applying correction formulas. For a clinic, the practical point is simpler: read ferritin next to an inflammation marker from the same draw, such as hs-CRP.

Ferritin is one of the markers where sex changes the reading. WHO's overload thresholds are split by sex and menstrual status, 150 µg/L for menstruating women and 200 µg/L for men and non-menstruating women. WHO found the available studies were not sufficient to justify changing its existing cutoffs by sex or age group, and its deficiency cutoff for apparently healthy adults (below 15 µg/L) is the same for women and men.

A clinic setting its own optimal ferritin levels should decide explicitly whether its bands differ for women and men, and on what basis.

No guideline defines an optimal ferritin level. The WHO and AGA cutoffs mark deficiency and possible overload for specific purposes. A band in between that a longevity clinic calls optimal is the clinic's own decision, and it should be documented like one.

• Name the guidelines the lower and upper bounds draw on.
• Decide whether bands differ by sex, and by menstrual status where relevant.
• Say how the clinic reads ferritin when an inflammation marker from the same draw is raised.
• Set a review date for the range.

Our guide to optimal vs reference ranges covers how to set and document clinic ranges.

WHO notes that ferritin increases in response to iron interventions and can be used to monitor them, and that the same method and sample type should be used for follow-up to keep variability down. That makes ferritin a marker clinics follow as a trend.

In LongevityEHR your clinic sets its own ferritin range, split by sex if you choose, and every released value is graded against the range that fits that patient. Each value keeps a snapshot of the range that applied on the day it was recorded, so later range changes never regrade history. See biomarker tracking.

Results come in through AI lab extraction: upload the lab PDF or image, and values are matched to your biomarkers, with unit mismatches flagged rather than converted. A provider reviews every result before it is released to the patient's portal. LongevityEHR classifies values against your ranges. It never interprets them, and your providers write the interpretation and the care plan.