Which essential biomarkers runners should track? The lab numbers that predict fatigue and low testosterone
Dr. Susan Carter, MD: Endocrinologist & Longevity Expert
Dec 04, 2025 · 15 min read
The essential biomarkers runners should track include vitamin D, iron and ferritin, magnesium and potassium, C reactive protein, testosterone, cortisol, blood glucose, and performance markers like VO2 max, lactate threshold, and resting heart rate. When those numbers drift, your training can feel harder, recovery slows, and injury risk rises even if your mileage looks “perfect.” ...