For decades, ferritin has been the main blood test used to estimate how much iron the body has stored. If ferritin falls below a certain level, doctors typically diagnose iron deficiency. If it sits within the lab’s reference range, everything is assumed to be fine.
But a growing wave of research in 2025 and early 2026 is challenging that simple picture. Scientists are now questioning whether many current ferritin “normal ranges” are set too low, and whether millions of people may be living with undiagnosed iron deficiency as a result.
Ferritin is a protein that stores iron, and measuring it in blood gives a rough idea of the body’s iron reserves. Historically, many labs have used very low ferritin cut-offs to define deficiency, sometimes around 10–15 ng/mL. However, recent large-scale analyses suggest that symptoms of iron deficiency can appear well before ferritin drops that low. Researchers are increasingly arguing that a ferritin level below about 30 ng/mL may indicate insufficient iron for many adults, even if it still falls within older “normal” ranges.
A 2025 analysis in JAMA Internal Medicine highlighted how changing ferritin thresholds dramatically alters how many people are classified as iron deficient. Using higher, more modern cut-offs identifies far more individuals who may benefit from investigation or treatment. This is particularly relevant for women, people with heavy menstrual bleeding, athletes, and those with chronic health conditions, who are already at higher risk of low iron.
At the same time, a major 2025 Lancet review emphasised that there is still no universally agreed ferritin threshold for iron deficiency. One reason is that ferritin does not only reflect iron stores. It also rises during inflammation, infection, liver disease, and metabolic stress. That means a “normal” or even high ferritin result can sometimes mask underlying iron deficiency if inflammation is present. Conversely, a low ferritin almost always indicates depleted iron stores.
This growing recognition has led to a shift in how clinicians interpret ferritin results. Rather than relying on a single number, many now consider the broader context: symptoms, inflammation markers, transferrin saturation, and overall health history. The trend is moving away from a rigid definition of iron deficiency based on very low ferritin, and toward a more nuanced understanding that includes earlier stages of depletion.
The implications for everyday health could be significant. Iron deficiency without anaemia has increasingly been linked with fatigue, reduced exercise tolerance, cognitive difficulties, restless legs, and mood changes. Researchers warn that waiting until haemoglobin drops and anaemia develops may mean people spend months or years experiencing preventable symptoms.
This evolving science does not mean everyone with a ferritin under 30 needs iron supplements. But it does suggest that the long-standing boundaries of “normal” may not reflect optimal health for many people. Over the next few years, experts expect further debate and possibly revised guidelines on what ferritin levels truly indicate adequate iron stores.
In other words, the ferritin test itself is not going away, but our understanding of what it means is changing. What counts as “normal” iron may soon look very different from what it did a decade ago.
Links to studies and sources:
JAMA Internal Medicine analysis on ferritin thresholds (2025): https://pubmed.ncbi.nlm.nih.gov/40853683/
Lancet review on iron deficiency definitions (2025): https://www.thelancet.com/journals/langlo/article/PIIS2214-109X%2825%2900266-9/fulltext
ASH publication on optimizing ferritin thresholds: https://ashpublications.org/blood/article/146/Supplement%201/1097/549603/Impact-of-optimizing-the-serum-ferritin-threshold
