Iron Avidity

Iron avidity is a state where the body is desperately trying to capture and use iron, but circulating iron is unavailable, even though iron may be present somewhere in the system or has recently been given.

It’s best thought of as functional iron starvation.

Clinically, it means:

• The bone marrow wants iron

• Transferrin is “hungry”

• But iron is not effectively reaching red blood cell production

How iron avidity shows up in labs

The classic pattern looks like this:

• Low transferrin saturation (often <10%)

• Low serum iron

• Normal or rising ferritin (or ferritin that doesn’t behave as expected)

• Persistent anemia or poor reticulocyte response

In other words:

The iron delivery truck exists, but it’s either empty or stuck in traffic.

Common causes of iron avidity

After iron therapy (very common)

• Occurs after IV iron or aggressive oral iron

• Ferritin rises (reflecting iron storage)

• TSAT remains low because iron is not yet mobilized

• Bone marrow still senses iron deprivation

This is transient but clinically important.

Inflammatory iron sequestration

Driven by hepcidin, the master regulator of iron:

• Inflammation ↑ → hepcidin ↑

• Iron trapped in macrophages and liver

• Serum iron falls

• Ferritin may be normal or high

Seen in:

• Chronic infection

• Autoimmune disease

• Chronic inflammatory states

• Post-viral syndromes

Ongoing blood loss

• Iron demand exceeds replacement

• Transferrin remains unsaturated

• Ferritin may appear “normal” if inflammation coexists

Malabsorption

• Oral iron not absorbed (celiac, autoimmune gastritis, PPIs)

• Bone marrow stays iron-starved

Functional marrow demand

• Rapid erythropoiesis (after transfusion or iron)

• Pregnancy

• Recovery from severe anemia

How iron avidity is different from iron deficiency

Iron avidity is iron deficiency physiology without empty stores.

Why iron avidity matters

If misunderstood, clinicians may:

• Stop iron too early

• Misdiagnose “iron overload”

• Miss ongoing inflammation or blood loss

The patient stays anemic—and frustrated.

Treatment of iron avidity

1. Treat the cause

This is the most important step.

• Control inflammation (autoimmune, infection)

• Stop blood loss (GI, gynecologic)

• Address malabsorption

• Reduce hepcidin drivers

Without this, iron therapy underperforms.

2. Continue iron—but thoughtfully

Iron avidity does not mean stop iron.

• Oral iron: often ineffective in inflammatory states

• IV iron: preferred when TSAT remains low despite ferritin rise

Iron is usually given in divided or staged doses, not all at once.

3. Time matters

Iron avidity after IV iron often improves over weeks, not days.

Recheck labs after 4–6 weeks, not immediately.

4. Support erythropoiesis

Iron doesn’t work alone.

Ensure adequacy of:

• Vitamin B12

• Folate

• Protein

• Copper (rare but important)

• Thyroid function

5. Avoid premature “iron overload” diagnosis

Ferritin alone is misleading.

True iron overload requires:

• Elevated ferritin and

• Elevated TSAT

Iron avidity has low TSAT.

Practical clinical example

A patient receives IV iron:

• Ferritin rises from 8 → 180

• TSAT stays at 6%

• Hemoglobin barely improves

This is iron avidity, not failure and not overload.
The marrow is still waiting for usable iron.

Bottom line

Iron avidity is a state of high iron demand with poor iron availability, often driven by inflammation, recent iron therapy, or ongoing loss.

Treatment is not stopping iron, but:

• Identifying the driver

• Using IV iron when needed

• Allowing time for mobilization

• Supporting marrow recovery

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Author

Scott Rollins, MD, is Board Certified with the American Board of Family Practice and the American Board of Anti-Aging and Regenerative Medicine.  He specializes in bioidentical hormone replacement for men and women, thyroid and adrenal disorders, fibromyalgia and other complex medical conditions.  He is founder and medical director of the Integrative Medicine Center of Western Colorado (www.imcwc.com) and Bellezza Laser Aesthetics (www.bellezzalaser.com).   Call (970) 245-6911 for an appointment or more information.