Biomarkers of Athlete Health: What to Track and Why (Practical Guide)

“Biomarkers” are measurable signals in blood (and sometimes urine/saliva) that can help you understand recovery, training tolerance, nutrition status, and hidden health issues. No single lab “proves” you’re fit or overtrained—patterns over time matter most, alongside performance, sleep, mood, and injury risk.

Recovery, inflammation, and training load

• hs-CRP (high-sensitivity C-reactive protein): A broad marker of inflammation. Useful when tracked over time; spikes can reflect infection, injury, or heavy training blocks.

• Creatine kinase (CK): Reflects muscle breakdown. It can rise a lot after intense lifting/sprints, so it’s most useful if you compare to your own baseline and timing from your last hard session.

• Resting glucose + A1C (and sometimes fasting insulin): Gives a window into energy balance and metabolic health. For endurance athletes, low-ish glucose isn’t always “better”—the goal is stability and good fueling.

Blood count and oxygen-carrying capacity

• CBC (complete blood count): Includes hemoglobin/hematocrit and red cell indices. Can flag anemia, infection, or issues that might affect endurance and recovery.

• Ferritin + iron studies (iron, transferrin saturation): Especially important for endurance athletes and anyone with fatigue. Ferritin can be influenced by inflammation, so it’s best interpreted with context (and sometimes with CRP).

Electrolytes, hydration, and muscle function

• Sodium, potassium, bicarbonate, magnesium (and sometimes calcium): Imbalances can affect performance, cramps, and recovery—especially in heavy sweaters or heat training.

• Kidney markers (creatinine, eGFR): Creatinine may run higher in muscular athletes; trends and context matter.

• Cystatin C: This is a useful kidney biomarker for those with more muscle mass, as it is independent of muscle mass.

Bone health and injury resilience

• 25-OH Vitamin D: Low vitamin D is common in winter climates and can be relevant for bone health and muscle function.

• Calcium, phosphate, ALP (alkaline phosphatase): Occasionally used when there are bone-stress concerns or recurrent stress injuries (guided by a clinician).

Energy availability and endocrine signals

• Thyroid panel (TSH ± free T4): Useful when fatigue, unexplained performance decline, or abnormal weight/temperature tolerance shows up.

• Sex hormones (context-dependent): Not a routine “performance lab,” but may be relevant if there are red flags like persistent fatigue, low libido, missed periods, repeated injuries, or stalled recovery. Interpretation should be careful and individualized.

Cardiometabolic baseline (often overlooked)

• Lipids (ApoB if available), blood pressure, A1C: Even athletes can have genetic cardiovascular risk. A periodic baseline is smart, especially with family history.

How to use biomarkers intelligently

1. Pick a baseline time: Do labs during a “normal” training week, not right after a competition or a brutal workout.

2. Repeat strategically: Track trends every few months if you’re making big training changes or addressing deficiencies.

3. Pair labs with real-world markers: Sleep, mood, resting heart rate, training log, injury frequency, and performance are just as important.

4. Don’t chase perfection: Labs fluctuate—focus on patterns and how you feel/function.

Our True North Metabolic athlete health clinic can help you optimize your health for performance.