Blood Biomarkers Every Lifter Should Track

If you're serious about maximizing muscle growth and performance, your blood holds answers that scale measurements simply can't provide. While tracking weights, reps, and body weight gives you surface-level feedback, blood biomarkers reveal what's happening under the hood—your hormonal environment, recovery status, and inflammation levels. Understanding these markers can help you make smarter training decisions, avoid overtraining, and optimize your muscle-building potential.

Why Bloodwork Matters for Lifters

Resistance training places significant stress on your musculoskeletal and endocrine systems. Your body responds by altering hormone levels, generating inflammation, and producing muscle damage markers. These physiological changes don't just disappear—they accumulate, and tracking them gives you insight into whether your training is producing the adaptations you want or pushing you toward burnout.

Most lifters rely on how they feel to gauge recovery. But subjective feelings are unreliable. Two people with identical workloads might have dramatically different biomarker profiles. Blood testing removes the guesswork and provides objective data you can act on.

Key Hormonal Markers

Testosterone

Testosterone is the primary anabolic hormone driving muscle protein synthesis, strength gains, and recovery. For male lifters, total testosterone levels typically range from 300-1,000 ng/dL, with free testosterone (the bioactive portion) constituting about 2-3% of total levels.

Research from 2025 examining physique athletes in competition preparation found that prolonged caloric restriction and high training volumes significantly decreased total testosterone and free testosterone while increasing cortisol [[PubMed, 2025]](https://pubmed.ncbi.nlm.nih.gov/39261323/). This hormonal suppression can blunt muscle growth and strength gains even when training intensity remains high.

Optimal range for lifters: Aim for the upper third of the reference range (typically 700-1,000 ng/dL for total testosterone). If you're in the low-normal range and experiencing fatigue, poor recovery, or stagnant lifts, addressing sleep, nutrition, and stress might naturally boost your levels.

Cortisol

Cortisol is your body's primary stress hormone. In acute doses, it helps mobilize energy for training. Chronically elevated cortisol, however, promotes muscle breakdown, impairs recovery, and suppresses testosterone production.

A 2025 study in mixed martial arts athletes found that cortisol and high-sensitivity C-reactive protein (hs-CRP) increased significantly during intensified training periods, while testosterone remained stable [[Nature, 2025]](https://www.nature.com/articles/s41598-025-09719-z). This suggests cortisol is often the first marker to spike when training load exceeds recovery capacity.

Optimal range for lifters: Measure morning cortisol (typically 5-25 μg/dL). The key isn't just the absolute value—it's the pattern. Elevated morning cortisol consistently signals overtraining or inadequate recovery.

The Cortisol-Testosterone Ratio

Rather than looking at hormones in isolation, the cortisol-testosterone ratio provides a clearer picture of your anabolic-catabolic balance. A elevated ratio (high cortisol relative to testosterone) indicates your body is in a catabolic state—breaking down tissue rather than building it.

Research suggests a ratio below 0.35 (cortisol in nmol/L divided by testosterone in nmol/L, multiplied by 10) is associated with optimal recovery and muscle-building conditions. Ratios above 0.5 suggest excessive stress and impaired adaptation.

IGF-1 (Insulin-Like Growth Factor-1)

IGF-1 mediates many of testosterone's anabolic effects and plays a direct role in muscle protein synthesis, satellite cell activation, and tissue repair. IGF-1 levels correlate with training adaptations—higher levels generally predict better strength and hypertrophy responses [[NCBI, 2025]](https://www.ncbi.nlm.nih.gov/books/NBK215705/).

Optimal range for lifters: IGF-1 typically ranges from 100-350 ng/mL in adults. Resistance training can naturally increase IGF-1, particularly when combined with adequate protein intake and sleep. If levels are low-normal, focus on sleep optimization and nutrition before considering supplementation.

Muscle Damage Markers

Creatine Kinase (CK)

Creatine kinase is an enzyme released into the bloodstream when muscle fibers are damaged. It's the most commonly measured marker of exercise-induced muscle damage. Baseline CK varies significantly between individuals (some people's baseline is 100 U/L, others is 300 U/L), so tracking your personal baseline is more useful than comparing to population averages.

A 2025 study found that CK remained persistently elevated during intensified training blocks, indicating ongoing muscle damage that hadn't fully resolved [[Nature, 2025]](https://www.nature.com/articles/s41598-025-09719-z). Elevated CK for more than 72 hours post-training suggests inadequate recovery.

Practical application: Test CK 48-72 hours after your hardest training session. If it's 3-5x your baseline, your volume or intensity exceeded recovery capacity. If it returns to baseline within 48 hours, your training load was appropriate.

LDH (Lactate Dehydrogenase)

LDH is another enzyme released during muscle damage. While less specific than CK (it's found in multiple tissues), elevated LDH alongside elevated CK confirms ongoing muscle damage. Research on elite athletes found that HMB supplementation reduced both CK and LDH levels after intense training [[PMC, 2022]](https://pmc.ncbi.nlm.nih.gov/articles/PMC7022312/).

Inflammation Markers

C-Reactive Protein (CRP)

CRP is a marker of systemic inflammation. Acute inflammation is necessary for muscle adaptation—it's part of the repair process. However, chronic elevated CRP indicates your body is in a persistent inflammatory state, which impairs recovery and can lead to overtraining syndrome.

The 2025 mixed martial arts study found hs-CRP increased significantly during high-stress training periods [[Nature, 2025]](https://www.nature.com/articles/s41598-025-09719-z). Elevated CRP combined with elevated cortisol is a red flag for overtraining.

Optimal range for lifters: hs-CRP below 1.0 mg/L is ideal. Between 1.0-3.0 mg/L indicates moderate inflammation; above 3.0 mg/L suggests chronic inflammation requiring attention.

When and How to Test

Timing Matters

For most accurate results, schedule blood tests first thing in the morning (fasting). This controls for daily fluctuations in hormone levels. For hormones like testosterone, which follow a circadian rhythm, morning values are most reliable.

Testing Frequency

• Baseline testing: Get comprehensive labs once per year during your off-season or maintenance phase
• During heavy training blocks: Consider testing every 4-8 weeks if pushing high volumes
• When feeling stale: If recovery feels off despite adequate sleep and nutrition, bloodwork can reveal hidden issues

What to Ask Your Doctor

Request these specific markers:

• Total testosterone, free testosterone
• DHEA-S (adrenal androgen precursor)
• Cortisol (morning)
• IGF-1
• hs-CRP
• Creatine kinase
• Thyroid panel (TSH, Free T3, Free T4)
• Lipid panel (testosterone is fat-soluble; lipid health affects hormone production)

Optimizing Your Biomarkers Naturally

Before pursuing medical interventions, optimize these factors that directly affect blood markers:

Sleep: Aim for 7-9 hours. Sleep deprivation elevates cortisol and suppresses testosterone more effectively than any drug. Nutrition: Adequate dietary cholesterol (needed for testosterone production), sufficient protein (1.6-2.2 g/kg), and healthy fats support hormonal health. Severe caloric restriction tanks testosterone. Training volume: More isn't always better. The 2025 research on physique athletes showed that excessive training volume during prep suppressed testosterone [[PubMed, 2025]](https://pubmed.ncbi.nlm.nih.gov/39261323/). Stress management: Chronic life stress elevates cortisol regardless of training. Meditation, time outdoors, and social connection all lower cortisol.

The Bottom Line

Blood biomarkers provide objective insight into your body's internal state—information that subjective feelings simply can't match. By tracking testosterone, cortisol, IGF-1, CK, and CRP, you can:

• Detect overtraining before it derails your progress
• Optimize training volume based on recovery capacity
• Ensure your hormonal environment supports muscle growth
• Make evidence-based decisions about your training and nutrition

You wouldn't drive a car without a dashboard. Why train without one? Your bloodwork is that dashboard—use it to fine-tune your approach and maximize your gains.