Essential biomarkers runners should track to run faster and avoid injury
Dr. Susan Carter, MD: Endocrinologist & Longevity Expert
Dec 04, 2025 · 14 min read
Key biomarkers runners should track include iron status (ferritin, hemoglobin), vitamin D, key hormones (cortisol, testosterone), blood-sugar markers, and inflammation/recovery signals — and many clinicians flag ferritin below about 30–35 ng/mL as a red flag for depleted iron stores that can reduce oxygen delivery and performance. Here’s how to interpret the numbers, spot problems before ...