Do runners tend to have low iron?

October 20, 2025 •

5 min read

Studies reveal that up to 56% of competitive runners experience some degree of iron deficiency, a condition often overlooked but critical to performance. This trend raises a key question for many athletes: do runners tend to have low iron, and if so, why does this happen and what can be done about it?

Quick Summary

Runners often develop iron deficiency due to increased iron loss from foot impact and sweat, combined with dietary limitations. Low iron levels can lead to fatigue and poor performance.

Key Points

Prevalence: Many runners, especially women and endurance athletes, are susceptible to low iron due to factors like increased training demands and higher losses.
Causes: Key culprits include foot strike hemolysis (damage to red blood cells), sweat loss, and the hormone hepcidin, which blocks iron absorption after exercise.
Symptoms: Common symptoms include persistent fatigue, poor workout recovery, unusual shortness of breath, and a noticeable decline in performance.
Diagnosis: A standard blood test can miss non-anemic iron deficiency. A serum ferritin test, which measures stored iron, is the most reliable diagnostic tool for runners.
Prevention: Dietary strategies involve consuming iron-rich foods, especially heme iron from meat. Vegetarians and vegans should focus on pairing non-heme iron sources with Vitamin C for better absorption.
Treatment: Correcting a deficiency often requires dietary changes and, if necessary, supplementation under a doctor's supervision. Never self-prescribe iron due to the risk of toxicity.
Timing: Timing intake correctly is crucial. Taking supplements or iron-rich foods away from calcium, coffee, or tea, and not immediately after intense exercise, can maximize absorption.

Why Iron is Critical for Runners

Iron is a vital mineral that plays a crucial role in athletic performance. It is a central component of hemoglobin, the protein in red blood cells responsible for transporting oxygen from the lungs to working muscles. Iron is also found in myoglobin, a protein within muscle tissue that extracts oxygen from hemoglobin. When iron levels are insufficient, the body's ability to create red blood cells and transport oxygen is compromised, leading to reduced energy production and fatigue. For a runner, this can translate to a noticeable decline in endurance, slower recovery, and overall diminished performance. Iron also plays a part in energy-generating pathways, further emphasizing its importance for sustained activity.

Key Reasons Runners Develop Low Iron

Several unique physiological factors put runners at a higher risk of developing low iron levels compared to the general population.

Foot Strike Hemolysis

One of the most significant causes is foot strike hemolysis, where the repetitive impact of a runner's foot hitting a hard surface (like asphalt) can damage and rupture red blood cells. While the body can usually recycle this lost iron, high-mileage training can cause a deficit over time, especially in taller or heavier athletes.

Increased Iron Loss from Sweat and Urine

Endurance exercise, especially in hot and humid conditions, increases iron excretion through sweat. While the amount of iron lost per individual session is small, it can add up significantly over time for heavy sweaters. Additionally, some evidence suggests minor iron loss can occur via the gastrointestinal tract and urine during intense training.

Elevated Hepcidin Levels

Intense exercise triggers an inflammatory response in the body, which leads to an increase in the hormone hepcidin. Hepcidin's function is to regulate iron absorption, and elevated levels can block the body from absorbing dietary iron for several hours post-workout. This makes proper timing of iron intake critical for runners.

Dietary Factors

Certain dietary choices are also major contributors to low iron among runners:

Vegetarian and Vegan Diets: The iron found in plant sources (non-heme iron) is less bioavailable and absorbed less efficiently than the heme iron found in animal products. Vegetarians and vegans must be more vigilant about consuming iron-rich plant foods and pairing them with vitamin C to enhance absorption.
Inadequate Energy Intake: Runners who follow low-calorie or energy-restricted diets may simply not consume enough iron to meet their increased needs.
Absorption Inhibitors: Substances in coffee, tea, cocoa, and calcium-rich foods can inhibit iron absorption, so timing their consumption away from iron-rich meals is important.

Symptoms of Iron Deficiency in Runners

Recognizing the signs of low iron can be difficult for runners, as many symptoms can be mistaken for simple overtraining. A blood test is necessary for a definitive diagnosis, but here are common signs to watch for:

Persistent and unusual fatigue
Shortness of breath during easy runs
Decline in running performance
Heavy, tired-feeling legs
Increased heart rate during exercise
Slow recovery from workouts
Increased frequency of illnesses or infections
Irritability or low mood
Pale skin

Diagnosis: The Importance of Ferritin

For runners, a standard Complete Blood Count (CBC) might show normal hemoglobin levels even when iron stores are low. This is known as non-anemic iron deficiency. The most crucial blood test for athletes is a serum ferritin test, which measures the body's stored iron. Ferritin levels provide an early warning sign before hemoglobin levels drop and true anemia develops. Many experts suggest a higher threshold for runners, with some recommending a ferritin level above 30 ng/mL for optimal performance.

Strategies to Prevent and Treat Low Iron

The Dietary Approach

For athletes with mild deficiency, or as a preventive measure, dietary adjustments are the first step. To maximize iron absorption, follow these tips:

Prioritize Heme Iron: Include lean red meat, poultry, and fish in your diet. Heme iron is the most easily absorbed form.
Boost Non-Heme Absorption: If consuming plant-based iron sources like lentils, beans, or spinach, pair them with a source of Vitamin C, such as citrus fruits, bell peppers, or strawberries.
Time Your Intake: Avoid drinking coffee, tea, or consuming high-calcium foods (dairy, fortified milks) within an hour or two of an iron-rich meal to prevent inhibiting absorption.
Use Cast Iron Cookware: Cooking with cast iron pans can leach small but meaningful amounts of iron into your food, particularly for acidic dishes.

Supplementation

For a diagnosed deficiency, a doctor may recommend oral iron supplementation. It is crucial to consult a healthcare provider for proper dosing and monitoring, as excess iron can be toxic.

Type of Supplement: Common and well-absorbed forms include ferrous sulfate or ferrous gluconate.
Timing: Taking supplements on an empty stomach or with Vitamin C enhances absorption. Avoid taking them around exercise, as hepcidin spikes can reduce effectiveness. Alternate-day dosing might also be effective for some individuals.

Comparative Guide to Iron Sources for Runners


Feature	Heme Iron	Non-Heme Iron
Source	Animal products (red meat, poultry, fish)	Plant sources (beans, lentils, spinach, nuts) and fortified foods
Bioavailability	High (15-35% absorbed)	Lower (2-20% absorbed)
Absorption Rate	Readily absorbed, not significantly impacted by dietary factors	Inhibited by compounds like phytates and polyphenols; enhanced by Vitamin C
Vegetarian/Vegan	Not suitable	Primary source for plant-based diets
Convenience	Found in common meats; easy to track intake	Requires careful pairing with Vitamin C to maximize absorption

Conclusion

In conclusion, it is common for runners, especially female and endurance athletes, to have low iron due to multiple physiological factors exacerbated by intense training. Foot strike hemolysis, increased sweat loss, and exercise-induced hepcidin spikes all contribute to depleting iron stores. These losses can significantly impair athletic performance by compromising oxygen transport and energy production. Runners must be proactive in managing their iron status by focusing on a diet rich in high-quality iron sources, optimizing absorption, and considering supplementation if directed by a medical professional. Regular monitoring of serum ferritin, not just hemoglobin, is essential for early detection and intervention. By taking these steps, athletes can maintain optimal iron levels, sustain their performance, and avoid the debilitating fatigue associated with iron deficiency, ensuring their long-term health and success in the sport. The IRONy in Athletic Performance provides a comprehensive review on this topic for interested readers.

Frequently Asked Questions

Runner's anemia is a term for a reduction in the concentration of iron in a runner's blood caused by strenuous exercise, leading to fatigue and compromised performance. It can involve low ferritin (stored iron) and, in advanced stages, low hemoglobin levels.

Foot strike hemolysis is the process where red blood cells are destroyed from the repetitive impact of running on hard surfaces. This constant destruction of red blood cells forces the body to use up more of its iron stores for replacement, potentially leading to a deficit.

Yes, female runners are at a significantly higher risk due to regular iron loss through menstruation, in addition to all other iron-depleting factors that affect both sexes.

You can improve iron absorption by pairing non-heme iron sources (from plants) with Vitamin C-rich foods, such as adding strawberries to oatmeal or bell peppers to a lentil dish. Avoiding coffee, tea, and calcium with iron-rich meals is also key.

Yes. Taking iron supplements when you don't need them can lead to iron overload, a condition that can cause damage to organs like the liver and heart. Always consult a doctor before starting any supplementation.

Hemoglobin is the iron-containing protein in red blood cells that carries oxygen, while ferritin is the protein that stores iron in your body. Ferritin levels can drop (indicating low stores) even when hemoglobin levels are still normal.

Recovery time varies depending on the severity of the deficiency. It can take several months of diligent dietary changes and/or supplementation under medical supervision to restore iron stores to a healthy level.