Even the fittest bodies on the planet don’t always show textbook-perfect bloodwork.
That’s the startling message from a new study published in the Journal of Science and Medicine in Sport, which analyzed blood test results from 2,525 Olympic athletes spanning the London 2012 to Paris 2024 Olympic Games.
The study, led by Armando Ferrera and colleagues, found that 62.6% of athletes had at least one biomarker outside clinical norms, a sobering statistic that challenges the long-standing assumption that elite fitness equals flawless internal health.
The Study: Largest-Ever Cohort of Olympian Blood Tests
This was no small sample.
Over a decade’s worth of lab data was pulled from the Institute of Sports Medicine and Science, examining athletes across all major disciplines, from endurance to skill sports. Researchers categorized athletes using the European Society of Cardiology’s framework and screened for a wide range of metabolic, hematological, and biochemical markers.
Key takeaways from the Ferrera et al., 2025 study:
- Total athletes analyzed: 2,525
- Female representation: 45.1%
- Overall abnormality rate: 62.6%
- Top findings:
- Dyslipidemia (high LDL): 20.4%
- Hypercortisolemia (elevated cortisol): 15%
- Iron deficiency: 9.7% overall, 16.5% in women
- Glucose intolerance: 8.4%
- Electrolyte imbalances: 27% (e.g., hypercalcemia and hyperkalemia)
- Vitamin D deficiency: 7.3%
When “Abnormal” Doesn’t Mean “Unhealthy”
So what does this mean? Should we be worried about elite athletes showing what would typically be considered red flags?
Experts say context is everything.
Performance physiologist Dan Garner, who broke down the findings on Instagram, noted, “That’s not fear-mongering, it’s physiology under extreme demand.”
Many so-called abnormalities may not signal disease but rather the body adapting to immense stress, including training overload, recovery periods, hormonal cycling, altitude exposure, and even travel.
For example, cortisol, a stress hormone, can spike after tough sessions or jet lag. Similarly, iron levels fluctuate depending on dietary intake, menstrual cycles, and gastrointestinal absorption.
As Nick Barringer, PhD, RDN, wrote, “Maybe many of these so-called ‘abnormalities’ are snapshots of athletes caught in phases of heavy training loads, recovery cycles, or hormonal periodization.”
Gender and Sport-Specific Trends
The data reveals fascinating insights when broken down by gender and sport type.
Gender Differences:
- Iron deficiency: 16.5% of women vs. 4.2% of men
- Hypercortisolemia: 17.1% in women vs. 13.2% in men
- Glucose intolerance: More prevalent in men (10.4%) than women (6%)
- Dyslipidemia: Higher in males (22%) than females (18.4%)
Sport Categories:
- Skill-based sports (e.g., golf, archery) had the highest abnormality rate at 70.6%, possibly due to lower cardiovascular conditioning and different training loads
- Power sports (e.g., weightlifting): 61.9%
- Mixed sports (e.g., soccer): 61.8%
- Endurance sports (e.g., running, cycling) fared best, though still had a 59.4% abnormality rate
A Shift in Perspective: From “Normal Ranges” to “Performance Ranges”
A central takeaway from the study — and echoed by practitioners — is that standard reference ranges were designed for the general population, not Olympic athletes. Comparing a world-class sprinter’s cortisol or lipid profile to that of a sedentary office worker misses the point.
Instead of relying on fixed cutoffs, experts now advocate for:
- Longitudinal monitoring, tracking biomarkers over time within the same athlete
- Within-athlete reference change values (RCVs): A 10–20% fluctuation in some markers may be just noise
- Contextual interpretation, considering timing — was the test taken during a heat camp, post-travel, or heavy training block?
As Dan Garner puts it, “Athletes don’t live in reference ranges. They live in performance ranges.”
Why This Matters
The implications go far beyond curiosity. These findings highlight the importance of precision medicine in elite sport.
Early Detection
Routine labs can catch nutritional deficiencies and metabolic issues before they spiral into performance decline.
Personalized Care
Sport- and sex-specific protocols allow teams to tailor recovery, diet, and training load more effectively.
Performance Optimization
Correcting low ferritin, regulating cortisol, and addressing glucose dysregulation can measurably improve endurance, recovery, and resilience.
Olympic athletes may look like superhumans, but their blood often tells a more complicated story. Over 60% of them show markers that would be flagged in a clinical setting. That doesn’t mean they’re unhealthy, but it does mean we need to rethink what “healthy” looks like at the outer limits of human performance.
Coaches, medical staff, and the athletes themselves should move beyond outdated reference ranges and embrace a model of performance-driven diagnostics, one that recognizes the uniqueness of elite physiology and meets it where it is.
Because when the fittest people on Earth are flagged as “abnormal,” maybe it’s time we change the baseline.
