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Pharmacokinetic Half-Life Engine

GLP-1 Blood Level &
Steady-State Accumulation Simulator

Because GLP-1s like Semaglutide and Tirzepatide take 5–7 days to decay by half, weekly injections compound in your bloodstream. Visualize your exact peak and trough levels.

Elimination Half-Life:7 Days (168h)
Peak Blood Concentration:24–48h Post-Injection
Steady State Reached:Weeks 4 to 5
Current Simulated Peak:0.97 mg in body

Estimated Active Blood Serum Curve (mg)

1 Bar = 1 Day
Day 1: 0.25 mg (Injection Day)
Day 2: 0.23 mg
Day 3: 0.21 mg
Day 4: 0.19 mg
Day 5: 0.17 mg
Day 6: 0.15 mg
Day 7: 0.14 mg
Day 8: 0.38 mg (Injection Day)
Day 9: 0.34 mg
Day 10: 0.31 mg
Day 11: 0.28 mg
Day 12: 0.25 mg
Day 13: 0.23 mg
Day 14: 0.21 mg
Day 15: 0.44 mg (Injection Day)
Day 16: 0.40 mg
Day 17: 0.36 mg
Day 18: 0.33 mg
Day 19: 0.29 mg
Day 20: 0.27 mg
Day 21: 0.24 mg
Day 22: 0.47 mg (Injection Day)
Day 23: 0.42 mg
Day 24: 0.38 mg
Day 25: 0.35 mg
Day 26: 0.32 mg
Day 27: 0.29 mg
Day 28: 0.26 mg
Day 29: 0.73 mg (Injection Day)
Day 30: 0.67 mg
Day 31: 0.60 mg
Day 32: 0.55 mg
Day 33: 0.49 mg
Day 34: 0.45 mg
Day 35: 0.41 mg
Day 36: 0.87 mg (Injection Day)
Day 37: 0.79 mg
Day 38: 0.71 mg
Day 39: 0.64 mg
Day 40: 0.58 mg
Day 41: 0.53 mg
Day 42: 0.48 mg
Day 43: 0.93 mg (Injection Day)
Day 44: 0.85 mg
Day 45: 0.77 mg
Day 46: 0.69 mg
Day 47: 0.63 mg
Day 48: 0.57 mg
Day 49: 0.52 mg
Day 50: 0.97 mg (Injection Day)
Day 51: 0.88 mg
Day 52: 0.79 mg
Day 53: 0.72 mg
Day 54: 0.65 mg
Day 55: 0.59 mg
Day 56: 0.53 mg
W10.25mg
W20.25mg
W30.25mg
W40.25mg
W50.5mg
W60.5mg
W70.5mg
W80.5mg

01.Why Side Effects Peak in Weeks 3–4

Even without increasing your prescribed dose, weekly injections of Semaglutide (7-day half-life) compound. By week 4, the residual medication from weeks 1, 2, and 3 elevates your total blood concentration to 1.8x your single injection dose. This is when appetite suppression and transient nausea reach clinical peak.

02.What Reaching Steady State Means

In pharmacology, steady state is achieved after 4 to 5 half-lives (~4–5 weeks). At this point, the rate of drug elimination equals the rate of weekly administration. Blood levels stabilize between predictable peak (day 2 post-shot) and trough levels (day 7 before next injection).

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