doi: 10.1111/j.1476-5381.1987.tb11206.x
Large amounts of B12 can potentially interact with some drugs used for diabetes, heartburn, seizures, and more
10.1016/j.phymed.2023.154658 15 EicheleD
Many patients use it proactively before travel, high-stress periods, or changes in season

Case Study #3: Athletic Performance Optimization Patient: 38-year-old male competitive age-group triathlete Chief Complaints: Declining recovery between training sessions, persistent low-grade injuries, inability to hit previous power numbers despite consistent training Baseline Assessment: IGF-1: 168 ng/mL (suboptimal for training load) Testosterone: 512 ng/dL (adequate but not optimal for performance goals) hs-CRP: 2.1 mg/L (chronic low-grade inflammation) Ferritin: 32 ng/mL (suboptimal for endurance athlete) Training metrics: 7-day recovery time after hard sessions (goal: 2-3 days) Treatment Protocol: Foundation: Address iron deficiency with supplementation, optimize nutrition timing around training Hormone optimization: Testosterone enanthate to achieve 850-950 ng/dL range Peptide therapy: Sermorelin 400 mcg nightly, 6 nights/week (timed around training schedule) Supporting interventions: Sleep optimization protocol, targeted anti-inflammatory nutrition 16-Week Results: IGF-1: 284 ng/mL (+69%) Recovery time: 2-3 days for hard sessions (71% improvement) FTP (functional threshold power): +18 watts Body composition: -2.1% body fat, +1.9 kg lean mass hs-CRP: 0.6 mg/L (normalized) Race results: Two age-group podiums in half-iron distance races Patient Report: The recovery improvement is dramatic
