Why Does Ferritin Go Up When Sick? A Detailed Look at Inflammation's Impact

October 1, 2025 •

4 min read

Ferritin, a protein that stores iron, is often used to assess the body's iron levels. However, over the past few decades, research has solidified ferritin's role as a key player in the inflammatory response, which answers the question, "Does ferritin go up when sick?" with a resounding yes, making it an unreliable measure of iron stores during illness.

Quick Summary

Yes, ferritin levels frequently rise when a person is sick due to the body's inflammatory response to infection or injury. This occurs because ferritin acts as an acute-phase reactant, sequestering iron to prevent pathogens from using it for growth, thus masking true iron stores.

Key Points

Ferritin is an Acute-Phase Reactant: The protein's levels rise significantly in response to inflammation and infection, not just changes in iron stores.
Masking True Iron Levels: During sickness, elevated ferritin can hide underlying iron deficiency, requiring additional tests for an accurate diagnosis.
Immune System Defense: The body increases ferritin to sequester iron from pathogens, a process known as nutritional immunity.
Clinical Context is Crucial: Test results must be interpreted alongside your symptoms and other blood test markers (like CRP) to understand their true meaning.
Re-test After Recovery: The most accurate assessment of baseline iron stores is done by re-testing ferritin levels once you are no longer sick.
Not Just for Iron Overload: High ferritin during illness doesn't automatically mean iron overload; it indicates an active inflammatory response.
Common Causes of High Ferritin: Infections, chronic inflammatory conditions, and liver disease are common reasons for elevated ferritin.

Understanding Ferritin's Dual Identity

Ferritin is a protein primarily known for storing iron safely within the cells, releasing it when the body needs it. A blood test measuring serum ferritin, therefore, provides a good indication of your body's iron reserves under normal circumstances. In fact, low ferritin is a hallmark of iron deficiency, which can lead to fatigue, weakness, and anemia.

However, ferritin has another, equally important role: it is an acute-phase reactant. This means that its levels in the blood will increase significantly in response to inflammation. This dual identity is why interpreting a ferritin test can be so complex, especially when you are not feeling well.

The Immune System's Clever Strategy

When your body is fighting off an infection or experiencing inflammation, your immune system initiates a complex defense strategy. The goal is to make the body a less hospitable environment for invading pathogens, which often need iron to multiply. To achieve this, the body reduces the amount of free-circulating iron and increases ferritin production to sequester and store iron safely inside the cells.

This process is mediated by pro-inflammatory cytokines, chemical messengers released by immune cells. Cytokines such as interleukin-6 (IL-6) signal the liver and other cells to produce more ferritin, causing its levels to spike in the bloodstream. This defense mechanism, known as 'nutritional immunity,' essentially starves the infectious agents of the iron they need to thrive. While effective for fighting off illness, it completely changes the interpretation of a ferritin blood test.

Common Illnesses and Their Effect on Ferritin

Many conditions that cause inflammation or infection can lead to elevated ferritin levels. Some of the most common include:

Acute Infections: Viral infections (like the flu, COVID-19, or Epstein-Barr virus), bacterial infections (such as pneumonia), and other acute illnesses often cause a temporary but significant increase in ferritin.
Chronic Inflammatory Conditions: Diseases like rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and chronic kidney disease are characterized by ongoing inflammation, which can keep ferritin levels consistently high.
Liver Disease: Since the liver is a primary site for ferritin storage, liver diseases such as fatty liver or chronic hepatitis can lead to elevated ferritin due to inflammation and cell damage.
Malignancy: Certain cancers, including some lymphomas and leukemias, can cause systemic inflammation and, consequently, high ferritin levels.

Decoding Your Lab Results While You're Under the Weather

If you get your ferritin tested while sick or shortly after recovering, your results may be misleading. Here is what to consider when interpreting your test results in the context of illness:

High Ferritin ≠ Iron Overload: An elevated ferritin reading during an infection or inflammatory episode does not necessarily indicate iron overload (hemochromatosis). It simply shows that your immune system is active. Your actual iron stores may even be low if you have chronic inflammation, a condition known as "anemia of chronic disease."
Look Beyond Ferritin: Because ferritin is compromised by inflammation, doctors will look at other iron-related tests to get a clearer picture of your iron status. These tests include serum iron, total iron-binding capacity (TIBC), and transferrin saturation (TSAT). In some cases, a C-reactive protein (CRP) test, another inflammation marker, may be ordered to help interpret the results.
Consider Re-testing Later: The most reliable way to accurately assess your baseline iron stores is to re-test your ferritin levels several weeks after you have fully recovered from your illness. This allows the inflammatory response to subside and the ferritin levels to normalize.

High vs. Low Ferritin: Understanding the Context


Feature	Low Ferritin	High Ferritin During Illness	High Ferritin (Without Inflammation)
Underlying Cause	Iron deficiency (inadequate intake, poor absorption, blood loss)	Inflammation due to infection or other acute illness	Iron overload (hemochromatosis), liver disease, frequent transfusions
Blood Test Interpretation	Suggests true iron deficiency; often accompanied by other abnormal iron studies	Can mask true iron deficiency; requires careful interpretation with other markers	Can indicate excessive iron storage that may harm organs
Clinical Symptoms	Fatigue, weakness, pale skin, hair loss	Symptoms of the underlying illness (fever, aches, cough, etc.)	Joint pain, abdominal discomfort, fatigue
Treatment Implications	Iron supplementation (oral or intravenous)	Addressing the underlying cause of inflammation	Phlebotomy (blood removal) or chelation therapy

The Bottom Line for Patients

When dealing with an illness, the focus should be on recovery. If your doctor orders a ferritin test during this time, they are aware of the potential impact of inflammation. The result should not cause undue alarm. For a deeper, more accurate understanding of your iron stores, follow your doctor's recommendations for re-testing once you're back to full health. Never start or stop any iron supplementation without consulting a healthcare professional, as ferritin levels can be a critical puzzle piece in managing your overall health.

To learn more about the broader context of iron storage and inflammatory markers, you can visit the National Institutes of Health for authoritative information on blood tests and interpreting results. Your doctor remains the best source of advice for your specific health situation.

Frequently Asked Questions

Yes, even a mild infection like a common cold or the flu can trigger an inflammatory response that causes your ferritin levels to rise temporarily. This is your body's natural defense mechanism at work.

The degree of elevation can vary widely depending on the severity and nature of the illness. In some severe cases of infection, such as sepsis or severe COVID-19, ferritin can reach very high levels, sometimes thousands of nanograms per milliliter, far exceeding the normal range.

Ferritin levels usually begin to decline as inflammation subsides. This can take several weeks or even longer, depending on the individual and the nature of the illness. Your doctor may recommend re-testing after a period of full recovery to get a more accurate reading of your iron stores.

This is a key example of how illness can complicate diagnosis. It is possible to have an inflammatory condition raising ferritin while simultaneously having low iron stores, a condition called 'anemia of chronic disease.' In this case, your doctor will look at other markers like transferrin saturation and C-reactive protein.

High ferritin is often a sign of an active inflammatory response. While it may not be dangerous on its own, it can be a marker for more severe inflammatory conditions. Your healthcare provider will interpret this result alongside your symptoms to determine if further investigation or treatment is needed for the underlying illness.

Yes, chronic stress can contribute to inflammation in the body. While a single stressful event is unlikely to cause a significant spike, prolonged stress can lead to systemic inflammation, which in turn can cause a slight elevation in ferritin levels over time.

If you take iron supplements, they will also contribute to your ferritin levels, complicating interpretation even further during an illness. It is best to discuss your iron intake with your doctor, who can advise on whether supplementation is appropriate and when to get a test for the most accurate results.