What is Red Blood Cell Count (RBC) & why is it important for athletes?

What Is Red Blood Cell Count (RBC)?

Red blood cells (RBCs) carry oxygen from your lungs to your muscles and carbon dioxide away from your tissues back to the lungs. A higher RBC count typically means better oxygen delivery, enhancing endurance, stamina, and recovery.

RBC count is a key performance biomarker for endurance athletes, especially when monitored alongside haemoglobin and haematocrit.

"RBC count reflects your capacity to transport oxygen – a fundamental driver of endurance and stamina. Both low and high counts can signal performance-limiting issues such as anaemia or dehydration. I recommend testing RBC every 3–6 months and interpreting it alongside haemoglobin, haematocrit and ferritin for a robust assessment of your oxygen-carrying capacity."

Dr Thom Phillips

What are normal red blood cell count (RBC) levels for athletes?

We looked at blood test data from EDGE customers and found the median RBC levels for women are 4.49 (10*12/L) and 4.96 (10*12/L) for men.

Here is a breakdown of RBC levels by age:

Source: EDGE customer blood test results Apr 2023 – March 2025.

The labs we used to analyse blood samples state a healthy range for RBC is generally between 4 – 5.2 (10*12/L) for women and 4.5 – 5.9 (10*12/L) for men.

Performance Benefits of Optimised RBC

• Improved Oxygen Transport

  More red blood cells mean greater aerobic capacity

• Better Recovery

  Oxygen delivery speeds muscle repair

• Increased VO₂ Max

  A well-maintained RBC count supports training adaptation

When to Test RBC Count

• During endurance training blocks or altitude exposure

• If suffering fatigue, poor recovery, or low haemoglobin

• To track response to iron supplementation

• Alongside haemoglobin, haematocrit, and ferritin for full insight

In Summary

• RBCs drive oxygen delivery and endurance

• Too few? Expect fatigue. Too many? Consider hydration and altitude factors

• Best interpreted with haemoglobin and haematocrit