Insulin Resistance and Iron Levels: What the Research Shows

By Dr. John Bartemus, DC, CFMP, Functional Medicine Charlotte, PC. Published October 28, 2026.

Iron is usually treated as a simple story: if it is low, take more; if you are tired, check your iron. But in people with insulin resistance and excess weight, iron behaves in ways that a standard reading can miss. Two studies, one in adults and one reviewing the evidence in children and adolescents, point to the same conclusion: iron and insulin resistance are tightly linked, and the link runs in both directions.

Watch: why is my iron low?

A quick explainer on how insulin resistance and inflammation can keep your iron low even when you supplement.

What the two studies examined

The first study, published in the Turkish Journal of Hematology in 2014, was a cross-sectional analysis of 206 patients seen at an obesity clinic plus 45 normal-weight controls. The researchers measured hemoglobin, serum iron, iron-binding capacity, ferritin, C-reactive protein (a marker of inflammation), and fasting glucose and insulin, and they calculated insulin resistance using the HOMA-IR formula. HOMA-IR is a standard estimate of insulin resistance derived from fasting glucose and insulin.

The second, published in Nutrients in 2025, is a review that pulls together the mechanisms connecting iron metabolism and insulin resistance, focused on children and adolescents with obesity. Together they give both a human data point and the biological explanation. The understanding of insulin resistance itself, and how to address it, is covered in my article on insulin resistance.

The 2014 finding: higher insulin resistance, lower iron

The adult study found a clear pattern. Serum iron decreased steadily as body weight increased, measuring roughly 14.9 in normal-weight controls, 13.6 in the mildly obese, and 10.9 micromoles per liter in the severely obese. When patients were split by insulin resistance, serum iron was significantly higher in the low HOMA-IR group than in the high HOMA-IR group (about 13.6 versus 11.6 micromoles per liter), a statistically significant difference. Hemoglobin was slightly lower with higher insulin resistance, and ferritin was slightly higher, though those two differences did not reach statistical significance.

The authors’ conclusion is the practical headline: elevated body weight and insulin resistance are associated with lower iron and hemoglobin, and people with insulin resistance may have iron deficiency without anemia. In other words, the iron available to the body can be low well before the blood count looks abnormal. This is observational, cross-sectional data (observational tier), so it demonstrates association rather than proving that insulin resistance causes the iron change.

How it works: inflammation and hepcidin

Why would insulin resistance lower iron? The most probable explanation is not that people are eating too little iron. It is that the iron gets trapped. Obesity and insulin resistance generate chronic low-grade inflammation, and inflammation raises a hormone called hepcidin, the body’s master iron regulator. When hepcidin rises, it reduces iron absorption in the intestine and locks iron inside storage cells, keeping it out of circulation. The body can hold plenty of iron while the usable supply runs low. This is sometimes called functional iron deficiency, and it is a direct consequence of the inflammatory state. The broader role of chronic inflammation in metabolic disease is something I cover in my article on the three stages of chronic inflammation.

Why ferritin can mislead you

This is where testing gets tricky. Ferritin is commonly used as a measure of iron stores, but it is also an acute-phase reactant, meaning it climbs in response to inflammation independent of actual iron status. In a person with obesity and insulin resistance, ferritin can read normal or even high while the iron the body can actually use is low. Relying on ferritin alone in this population can give false reassurance. A fuller evaluation, including serum iron, iron-binding capacity or transferrin, and markers of inflammation, paints a more honest picture. If you have felt tired despite “normal” labs, this is one of the mechanisms worth understanding, as I discuss in my article on being tired when your bloodwork looks normal.

The relationship runs both ways

The 2025 review adds an important counterbalance: this is not simply “insulin resistance lowers iron.” Iron influences insulin, and insulin influences iron. A few threads from the review:

• Too much stored iron can worsen insulin resistance. High body iron, particularly in the liver, increases oxidative stress and reactive oxygen species, interferes with insulin signaling, and lowers adiponectin, a hormone that supports insulin sensitivity.
• High insulin promotes iron retention. Elevated insulin stimulates ferritin production and can suppress hepcidin in ways that increase iron absorption and storage, feeding a cycle.
• Iron deficiency can also worsen insulin resistance. Low iron may impair mitochondrial function and push cells toward less efficient energy pathways, which can disrupt glucose handling.

So both ends of the iron spectrum, deficiency and overload, connect to insulin resistance, and the direction can differ by person and context. That nuance is exactly why a one-size rule, whether “everyone should take iron” or “everyone should avoid it,” is the wrong approach.

What this means for you

The combined message is practical and root-cause in spirit:

• Do not treat low iron in isolation. If iron is low in the setting of insulin resistance or excess weight, the inflammation driving hepcidin is part of the problem. The 2025 review notes that oral iron alone may not be the best fix, and that combining it with weight loss and reduced inflammation may work better.
• Test beyond ferritin. Because ferritin rises with inflammation, ask about a fuller iron panel and inflammatory markers rather than relying on a single number.
• Address the terrain. Weight reduction and lowering inflammation can help restore iron balance, according to the review. That makes metabolic health and iron status one connected target, not two separate ones.
• Individualize. Since both too little and too much iron can be a problem, supplementation decisions should be made with a clinician using actual testing, not guesswork.

The honest limits

Both papers have boundaries worth stating. The 2014 study is cross-sectional and observational, so it shows association, not causation, and it was conducted in adults at a single center. The 2025 paper is a review rather than a trial, and its primary focus is children and adolescents, so some mechanisms may not translate directly to every adult. The review’s authors are explicit that longitudinal studies and randomized trials are still needed, particularly to compare iron supplementation against integrated weight management. What is consistent across both is the core relationship: iron metabolism and insulin resistance are intertwined, largely through inflammation, and treating them as connected is better supported than treating them separately.

Frequently asked questions

Can insulin resistance cause low iron?

It is associated with lower serum iron. A 2014 study found iron was significantly higher in people with low insulin resistance than high, and fell as weight rose. The likely driver is inflammation raising hepcidin, which traps iron, producing iron deficiency without anemia. This is observational data.

Why is my ferritin high but my iron low?

Ferritin is an acute-phase reactant, so it rises with inflammation, which is common in insulin resistance and obesity. It can read normal or high while usable iron is low. A fuller iron panel with inflammatory markers is more reliable than ferritin alone.

Does iron deficiency make insulin resistance worse?

There is mechanistic evidence that it can, by impairing mitochondrial function and glucose handling. The relationship is bidirectional: insulin resistance can lower available iron, and low iron can worsen insulin resistance.

Can too much iron also cause insulin resistance?

Yes. High stored iron, especially in the liver, raises oxidative stress, interferes with insulin signaling, and lowers adiponectin. Both too little available iron and too much stored iron connect to insulin resistance.

Will weight loss improve my iron levels?

The 2025 review reports that weight reduction can help restore iron balance, likely by lowering inflammation and hepcidin. For obesity-related iron deficiency, the authors suggest combining any iron therapy with weight loss rather than relying on iron alone. Individualize this with a clinician.

About the author: Dr. John Bartemus, DC, CFMP, is a functional medicine practitioner, educator, speaker, and Amazon international number one best-selling author, focusing on cardiometabolic health, insulin resistance, and root-cause medicine through Functional Medicine Charlotte, PC.

This article is for educational purposes only and is not medical advice. Do not start or stop iron supplementation without testing and guidance from a qualified clinician, since both iron deficiency and iron overload carry risks.

References

1. Altunoglu E, Muderrisoglu C, Erdenen F, Ulgen E, Ar MC. “The Impact of Obesity and Insulin Resistance on Iron and Red Blood Cell Parameters: A Single Center, Cross-Sectional Study.” Turkish Journal of Hematology, 2014;31:61-67. DOI 10.4274/Tjh.2012.0187.
2. Calcaterra V, Cena H, Bolpagni F, Taranto S, Vincenti A, Madini N, Diotti M, Quatrale A, Zuccotti G. “The Interplay Between Iron Metabolism and Insulin Resistance: A Key Factor in Optimizing Obesity Management in Children and Adolescents.” Nutrients, 2025;17:1211. DOI 10.3390/nu17071211.