The 5 Blood Markers Every Athlete Should Actually Track

Most routine bloodwork screens for disease but misses the performance-relevant markers that actually tell you how your body is functioning. Here's what to ask for and what the numbers mean.

A standard annual physical typically includes a basic metabolic panel, CBC, and a lipid panel. This covers your organ function and looks for disease markers. What it doesn't tell you is whether you're deficient in the nutrients that drive performance and recovery, whether your hormones are optimized, or whether your inflammatory load is high enough to be impairing adaptation to training.

For anyone training seriously — or anyone interested in optimizing health beyond just the absence of diagnosable disease — here are the five markers worth adding to your next blood panel.

1. Vitamin D (25-hydroxyvitamin D)

Vitamin D is technically a hormone precursor involved in immune function, bone metabolism, muscle function, inflammation regulation, and testosterone production. Deficiency is widespread — estimated to affect 40–50% of the US population — and athletes who train indoors or live in northern latitudes are particularly susceptible.

Optimal range for athletes is generally considered 40–60 ng/mL (some functional medicine practitioners argue for 50–70). The standard lab "normal" range often goes down to 20 ng/mL, which is sufficient to prevent clinical deficiency but may not be optimal for performance and recovery. If you're below 40, supplementation is worth pursuing.

2. Free testosterone (and total testosterone)

Total testosterone tells you the overall amount of testosterone circulating. Free testosterone tells you how much is biologically active — not bound to sex hormone binding globulin (SHBG) and therefore available for use by tissues. You can have normal total testosterone with low free testosterone if SHBG is elevated. Both numbers matter.

For men: low-normal or below-normal testosterone in the context of fatigue, difficulty maintaining muscle, low libido, and mood changes is worth addressing — whether through lifestyle optimization or, if levels are genuinely deficient, medical intervention. For women: testosterone plays a meaningful role in energy and body composition as well, and is frequently underassessed.

3. Ferritin (iron storage)

Ferritin is the storage form of iron and a more sensitive marker of iron status than serum iron alone. Low ferritin — even in the absence of frank anemia — is associated with fatigue, decreased endurance performance, impaired recovery, and brain fog. Endurance athletes, particularly women, are at significant risk for iron deficiency.

Standard lab ranges often list ferritin as "normal" at levels as low as 10–12 ng/mL for women. Most sports medicine practitioners consider anything below 30 ng/mL to be sub-optimal for athletic performance, with 50–100 ng/mL being a more appropriate target range.

4. High-sensitivity C-reactive protein (hs-CRP)

hs-CRP is a sensitive marker of systemic inflammation. Standard CRP testing used in clinical medicine detects elevated inflammation from acute illness or injury. High-sensitivity CRP can detect the low-grade chronic inflammation that isn't causing acute symptoms but is associated with cardiovascular disease risk, impaired adaptation to training, and metabolic dysfunction.

For general health and performance, hs-CRP below 1 mg/L is ideal. Levels between 1–3 mg/L suggest moderate inflammatory load that warrants attention (sleep, dietary quality, body composition, stress). Levels consistently above 3 mg/L in the absence of acute illness are a meaningful red flag.

5. HbA1c (glycated hemoglobin)

HbA1c reflects average blood glucose over the previous 2–3 months — it's the gold standard marker for glucose regulation status. Below 5.7% is considered normal. 5.7–6.4% is pre-diabetic. 6.5% and above is diabetic. For performance optimization, the lower end of normal is associated with better energy stability, body composition, and long-term metabolic health.

HbA1c is more informative than a fasting glucose alone because it captures the full range of glucose variation over time rather than a single snapshot.

How to order these tests

Ask your primary care physician to add these to your annual labs. Most are covered under standard preventive care. If your physician isn't receptive or you want to order them independently, direct-to-consumer lab services (LabCorp through platforms like Ulta Lab Tests, or Quest Diagnostics) allow you to order your own bloodwork without a physician referral.

The bottom line

You can't optimize what you haven't measured. These five markers are cheap, widely available, and provide a meaningful picture of the hormonal, nutritional, and inflammatory status that drives performance and recovery. Get the data, then make decisions from it.