One of the most common questions patients ask is: "Why do I have zero appetite for 4 days, and then feel hungry on Day 5 or Day 6?" The answer lies in exponential pharmacokinetic decay: C(t) = C₀ · 0.5^(t / t½).
- Tirzepatide (Mounjaro® / Zepbound®): Biological half-life of 5 days (120 hours). By Day 5, active concentration is at 50%; by Day 7, it reaches ~37.9% before your next dose.
- Semaglutide (Ozempic® / Wegovy®): Biological half-life of 7 days (168 hours), reaching exactly 50% at the 7-day mark.
