The Performance Impact of Blood Donation: When is it Okay to Return to Cycling After Giving Blood?

Tips for optimal performance and a safe and satisfying return to cycling after giving blood and donating the gift of life

Return to Cycling After Giving Blood cyclist riding on open road
Photo courtesy of TLBVelo photography @

Blood is essential to life. It’s as crucial as the air we breathe, and there’s no replacement other than someone else sacrificing theirs. Blood donation is a selfless act that can help save lives and improve health outcomes. Yet, many endurance athletes are reluctant to donate because of the potential performance effects. 


According to the World Health Organization, an estimated 118.4 million annual blood donations occur globally. In the United States alone, someone needs blood or platelets every two seconds. More than 36,000 blood donations are needed daily to meet the US blood transfusion demand.


The numbers don’t add up. 4.5 million Americans need a blood transfusion yearly, but less than 10 percent of the population chooses to donate. The demand for blood is critical, and COVID concerns worsened the situation.

However, some cyclists may worry about the impact of donating blood on their cycling performance and safety. After all, cycling requires a lot of physical exertion and endurance, which can be affected by changes in blood volume and composition.


It’s vital for cyclist’s to know the effects of donation on performance and how to stay safe and healthy after giving blood. Understanding the risks and benefits will help you make an informed decision and ease your apprehension about contributing to the life-giving cause.

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What You Need To Know About Returning to Cycling After Giving Blood

Understanding how donating blood can affect your cycling performance requires a basic knowledge of the science of blood and how it relates to endurance sports. Blood comprises several factors, including red blood cells, white blood cells, platelets, and plasma. Each component plays a different role in the body, but we’ll focus on red blood cells for cycling purposes.


Red blood cells carry oxygen from the lungs to the rest of the body, including our cycling muscles. The amount of oxygen the blood can hold depends on the hemoglobin level, a protein found in red blood cells that bind to oxygen molecules. Hematocrit, another measure of blood composition, refers to the percentage of red blood cells in the blood.


When you donate blood, you’re essentially giving away some of your red blood cells, which can temporarily reduce your hemoglobin and hematocrit levels.

It has several effects on your body, including:
  • Reduced oxygen-carrying capacity: With fewer red blood cells, your blood may not be able to carry as much oxygen to your muscles, which can lead to fatigue, weakness, and decreased performance.


  • Increased heart rate: Your heart may have to work harder to pump blood around your body to compensate for the reduced oxygen supply. It can lead to an increased heart rate, which can be challenging to sustain during endurance exercise and start you at a disadvantage.

  • Dehydration: Giving blood can also cause a temporary loss of fluids, leading to dehydration if you don’t drink enough water. Dehydration can further impair your cycling performance through overheating and increase the risk of heat exhaustion or heat stroke.

How Much Do the Levels Decrease After Giving Blood?

The decrease in red blood cell count, hemoglobin, hematocrit, and blood volume can vary from person to person and depend on several factors, such as the amount of blood drawn and the individual’s initial levels. 


Generally, a standard blood donation of one pint (about 470 mL) can cause a decrease of around 5-10% in red blood cell count, 5-10% in hematocrit, 5-10% in hemoglobin, and 8% in blood volume. 


However, the body can quickly compensate for this loss of blood volume by mobilizing fluid from other tissues and increasing heart rate and cardiac output.

How Much Does Giving Blood Affect Endurance and Cycling Performance?

After giving blood, hemoglobin levels decrease by 7 percent on average and remain compromised for at least two weeks after donation. By day 14, they usually recover fifty percent, to a 4 percent decrease from pre-donation levels, according to a recent study in Transfusion


Your hematocrit level will also decrease for the first few days. Typically 5 percent for 48 hours after donation and recovers within two weeks. Hematocrit recovers more quickly than hemoglobin because newly synthesized cells have a lower hemoglobin concentration than mature cells.


The decrease in oxygen-carrying capacity and delivery accounts for a 7 percent decrease in VO2 max (the maximum amount of oxygen a person can consume during exercise) 24-48 hours after donation. After three days, VO2 max is near normal levels, suggesting that blood volume returns to near-normal. Heart rate increases compensate for the decreased hemoglobin to restore oxygen delivery to normal. 


VO2 max is a measure of peripheral tissue oxygen utilization. On day three after donation, once oxygen delivery is back to near-normal levels, VO2 max also recovers, as cellular metabolism is unaffected by hemoglobin levels alone.


Along with the decrease in VO2 max, measured maximal exercise capacity and time to exhaustion when performing at threshold also decreases by about 10 percent after a blood donation, then fully recovers by one week. In the above study, TT performance declined by about 5 percent and returned to baseline in two weeks.

In addition to the decrease in red blood cells, blood donation can also reduce iron levels and ferritin concentration, which can further impact athletic performance. Iron is essential for hemoglobin production. Without enough iron, the body can’t produce enough hemoglobin, leading to decreased muscle oxygen delivery.

Return to Cycling After Giving Blood hemochromatosis image
A word of caution! Only take iron supplements after knowing your pre-donation ferritin level first. Read “Being an Endurance Athlete Almost Cost Me My Life—A Personal Story of Hemochromatosis” to learn why! 

After donating blood, it typically takes 4-6 weeks for the body to fully replenish the red blood cells, hemoglobin, hematocrit, and blood volume lost during the donation. However, this time frame can vary depending on age, overall health, and diet. Taking steps to support the body’s recovery is essential to mitigate the impact on endurance and cycling performance.

Tips For a Safe Return to Cycling After Giving Blood

If you plan to cycle after donating blood, take some precautions to ensure you don’t put too much strain on your body. Here are some tips for cycling after giving blood:


  1. Wait 24 hours before intense rides: Give your body time to recover from the blood donation before exercising. It’s okay if you find the first few rides a bit more challenging.


  1. Start slow: Begin with a low-intensity ride and gradually increase the intensity as you feel comfortable. Avoid pushing yourself too hard, especially on hills or during sprints, until you know how you’re body will react.


  1. Stay hydrated: Drinking plenty of water before, during, and after your ride is essential to help your body recover and prevent dehydration.


  1. Eat well: Eat a balanced meal with iron-rich foods like leafy greens, red meat, and legumes. It will help to replenish the lost iron from blood donation and support your body’s recovery. Be sure to monitor hemochromatosis risk first.


  1. Listen to your body: If you feel lightheaded, dizzy, or fatigued during your ride, stop and rest until you feel better.


  1. Avoid cycling in extreme weather conditions: High temperatures or humidity can put extra stress on your body, so it’s best to avoid cycling in very hot or humid weather.


  1. Monitor your heart rate: Keep an eye on your heart rate while cycling, as it may be higher than usual due to the reduced number of red blood cells in your body. Slow down or take a break if your heart rate is significantly higher than usual.


  1. Rest up: Getting adequate sleep and rest can help your body recover more quickly from the blood donation process.


If you have any questions, consult with your doctor before engaging in any physical activity after donating blood, especially if you have any underlying health conditions.

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Plan For Your Return to Cycling After Giving Blood

If you know you will be donating blood, plan your training schedule accordingly. Make your donation appointment for a rest or recovery day. 


Avoid intense workouts or races for at least 24-48 hours. Studies show that giving blood will affect endurance performance for two weeks, so don’t donate within 14 days of a big event.


It’s also worth noting that some competitive cycling organizations may have specific rules or guidelines around blood donation, so be sure to consult with your coach or governing body if you have any questions or concerns.

Conclusion—Return to Cycling After Giving Blood

Donating blood can significantly impact a competitive cyclist’s training and performance. However, the satisfaction of sharing the gift of life outweighs the inconvenience and short-term competitive challenges.


Athletes need to take certain precautions and adjust their routines to minimize the impact of the donation process. By planning, staying hydrated, eating well, getting adequate rest, and monitoring their symptoms, cyclists can continue to train effectively and avoid setbacks after donating blood. 


As with any health-related issue, it’s always best to consult a healthcare professional if you have any concerns or questions about donating blood and its impact on your cycling performance. With proper preparation and care, cyclists can continue pursuing their athletic goals without sacrifice.

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Fabrice Bordeaux
Fabrice Bordeaux
3 months ago

Good article, I was looking at exactly this analysis and numbers. Thanks Christopher Schwenker!

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