Can the flu lower your iron? Understanding the link between infection and anemia

November 30, 2025 •

4 min read

According to scientific research, a person's iron levels can drop temporarily during a viral infection like the flu. This drop is part of the body's natural inflammatory response and can lead to a condition called anemia of inflammation. Understanding this complex process is crucial for effective recovery and preventing further complications.

Quick Summary

The body's inflammatory response to the flu triggers a temporary drop in circulating iron levels by sequestering it in cells, an innate defense mechanism. This can cause anemia of inflammation, which typically resolves with recovery. Understanding the process is key for recovery.

Key Points

Inflammation Drives Iron Changes: The body's inflammatory response to the flu causes a temporary, functional iron deficiency by altering how iron is regulated and distributed.
Hepcidin is the Key Regulator: The hormone hepcidin is elevated during infection and blocks the release of iron from storage, effectively sequestering it from the bloodstream.
Anemia of Inflammation Occurs: This process can result in anemia of inflammation, a condition where there is low circulating iron, but total iron stores are not necessarily depleted.
Recovery Normalizes Levels: In most healthy individuals, this effect is temporary, and iron levels naturally return to normal as the infection and inflammation resolve.
Pre-existing Iron Deficiency is a Risk Factor: Individuals with pre-existing iron-deficiency anemia are more susceptible to severe drops in iron levels and may experience worsened symptoms during illness.
Oral Iron Absorption is Reduced: During the height of inflammation, oral iron supplementation may be less effective due to the action of hepcidin blocking intestinal absorption.
Treating the Infection is Primary: The most effective way to correct anemia of inflammation is to resolve the underlying viral infection and let the body's natural processes restore balance.

The Body's Defense Mechanism: Anemia of Inflammation

When you get the flu, your body initiates a strong immune response to fight the invading virus. This response involves widespread inflammation and the release of pro-inflammatory signaling proteins called cytokines. This inflammatory process is the central reason behind the drop in circulating iron, and it's an evolutionary defense strategy known as 'nutritional immunity'. Pathogens, especially bacteria, need iron to multiply rapidly, so the body's defensive action is to remove iron from the bloodstream and hide it away in storage cells, making it less available for pathogens to use.

The Role of Hepcidin, the 'Master Iron Regulator'

The linchpin of this process is a hormone called hepcidin, which is produced primarily by the liver. During inflammation, levels of the cytokine interleukin-6 (IL-6) increase, which directly stimulates the liver to produce more hepcidin.

Increased hepcidin levels have a domino effect on iron metabolism:

Blocks Iron Export: Hepcidin binds to and degrades ferroportin, the only known protein that exports iron from cells into the bloodstream.
Traps Iron in Macrophages: By degrading ferroportin, hepcidin effectively traps iron inside macrophages, which are immune cells responsible for recycling iron from old red blood cells. This stops the recycling process and keeps iron out of circulation.
Inhibits Intestinal Absorption: Hepcidin also acts on intestinal cells, reducing their ability to absorb dietary iron from food.

This leads to low iron levels in the blood, a condition known as hypoferremia, and creates an iron-restricted environment for erythropoiesis—the production of new red blood cells. This is functionally an 'anemia of inflammation' (AI), even if overall body iron stores are not depleted.

Recovery and Normalization of Iron Levels

In most cases, this drop in iron is temporary. As the body successfully clears the influenza virus and the inflammatory response subsides, hepcidin levels decrease, and iron is released back into the bloodstream. For most healthy individuals, normal iron balance is restored as they recover from the illness. However, the time it takes for iron levels to fully normalize can vary. One study noted that after a febrile illness like influenza, ferritin levels can remain elevated for more than a month, which can mask an underlying iron deficiency. For people with pre-existing iron-deficiency anemia, the flu can make symptoms significantly worse.

The Difference Between Anemia of Inflammation and Iron-Deficiency Anemia

It is important to distinguish between anemia caused by the flu (AI) and classic iron-deficiency anemia (IDA). While both result in low circulating iron, their underlying causes and treatment approaches differ significantly.


Feature	Anemia of Inflammation (AI)	Iron-Deficiency Anemia (IDA)
Cause	An inflammatory state from infection (e.g., flu)	Inadequate iron intake, absorption, or chronic blood loss
Hepcidin Levels	High	Low
Circulating Iron	Low	Low
Ferritin Levels (Iron Stores)	Normal to High (iron is trapped in storage)	Low (iron stores are depleted)
Transferrin Levels	Low (suppressed by inflammation)	High (body trying to find more iron)
Treatment Focus	Resolving the underlying infection	Addressing iron deficiency, often with supplementation

Supporting Your Body's Recovery

For most people, managing the symptoms of the flu is the best approach to help iron levels recover naturally. Eating a balanced diet rich in iron can support the body as it recovers. Vitamin C, found in citrus fruits and leafy greens, is particularly helpful as it enhances the absorption of iron. During periods of high inflammation, oral iron supplements may be less effective due to the increased hepcidin blocking absorption. However, those with pre-existing iron-deficiency should follow their doctor's advice on supplementation. Rest, hydration, and treating the primary infection are the most effective ways to aid the body's return to normal iron homeostasis. In rare, severe cases, such as in patients with compromised immune systems or other underlying conditions, a doctor may need to intervene to manage the hematological effects of the viral illness.

For more clinical context on how viral infections can impact iron metabolism and health outcomes, consult the review paper from the University of Cambridge, "Low iron levels resulting from infection could be key trigger of long COVID".

Conclusion

In summary, the flu can indeed lower your circulating iron levels as a result of the body's inflammatory immune response. This is a temporary process known as 'anemia of inflammation' where the body sequesters iron to hinder viral growth. While it may cause temporary fatigue, it typically resolves naturally as you recover. The mechanisms involve the hormone hepcidin blocking the release of iron from stores and reducing its absorption. By focusing on treating the flu and supporting your body with proper nutrition, you can help restore your iron balance. If symptoms persist or you have underlying health issues, consult a healthcare professional for guidance on managing your iron levels post-illness.

Can the Flu Lower Your Iron: A Recap of Key Takeaways

Inflammation is the Cause: The drop in iron is triggered by the body's inflammatory response to the influenza virus.
Hepcidin Traps Iron: The hormone hepcidin is produced in response to inflammation and prevents iron from leaving storage cells and being absorbed from the gut.
Temporary Low Blood Iron: This leads to a temporary state of low iron in the bloodstream, but not necessarily a depletion of total body iron stores.
Resolves with Recovery: For most healthy people, iron levels return to normal as the flu-related inflammation subsides.
Can Exacerbate Pre-existing Conditions: Individuals with pre-existing iron-deficiency anemia may experience a worsening of symptoms during a viral illness.
Diet and Rest Aid Recovery: A balanced diet with iron-rich foods and vitamin C, combined with proper rest, supports the body's natural recovery process.
Consult a Doctor for Concerns: If you experience persistent symptoms, it is best to consult a healthcare provider for proper diagnosis and guidance.

Frequently Asked Questions

A drop in circulating iron levels is a common physiological response to a viral infection, but it doesn't necessarily lead to clinically significant anemia in every healthy individual. The degree of change varies based on the severity of the illness and a person's baseline health.

Symptoms of low iron, such as fatigue, lethargy, or shortness of breath, can overlap with post-flu recovery. If you are concerned, a blood test to check your serum iron, ferritin, and C-reactive protein (CRP) levels can help your doctor determine if you have anemia and what type.

During the peak of an inflammatory illness like the flu, oral iron supplements may not be absorbed effectively due to elevated hepcidin levels. It's generally best to support recovery with a balanced diet. Consult your doctor, especially if you have pre-existing iron deficiency.

The flu itself causes a functional iron deficiency, where iron is sequestered, rather than a true deficiency from depleted stores. However, if a person already has iron-deficiency anemia, the flu's inflammatory effects can worsen their condition.

Iron levels typically return to normal as inflammation subsides with recovery. For some, iron status markers like ferritin might take a month or more to fully normalize after a febrile illness. Symptoms usually improve much sooner.

This is an ancient survival mechanism called 'nutritional immunity'. By removing iron from the bloodstream and making it less available, the body limits the ability of invading pathogens, particularly bacteria, to use the iron they need to grow and multiply.

Focus on iron-rich foods like red meat, poultry, leafy greens, beans, and lentils. Pair these with foods high in vitamin C, such as citrus fruits, to enhance absorption. While dietary support is helpful, resolving the underlying infection is the main driver of iron normalization.

For most healthy people, the anemia of inflammation caused by the flu is mild and temporary. However, in vulnerable populations like young children or those with chronic conditions, severe cytopenias including anemia can occur and require medical attention. If concerned, always speak with a doctor.