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GLP-1/GLP-3 Half-Life Calculator & Dose Tracker
GLP3 Planner tracks drug levels for GLP-1 and GLP-3 receptor agonists: Retatrutide, Semaglutide (Ozempic®/Wegovy®), and Tirzepatide (Mounjaro®/Zepbound®). Enter your doses and see exactly how much compound is in your system at any point. Read more about why we created GLP3 Planner here.
How It Works
Enter your compound, dosing schedule, and injection times. The calculator models drug concentration using published pharmacokinetic data, so you can see how much compound is active in your system at any point. Useful for understanding dose overlap, planning titration, or talking to your provider about adjustments.
Visit our main GLP-1 dose calculator to explore all available compounds and features.
How Half-Life is Calculated
GLP3 Planner uses pharmacokinetic modeling based on published half-life data:
- Retatrutide: ~6 days half-life
- Tirzepatide: ~5 days half-life
- Semaglutide: ~7 days half-life
The calculator uses exponential decay to show how concentration drops over time. You can see where doses overlap and when steady-state kicks in (typically after 4-5 half-lives).
See the full PK methodology → — the one-compartment Bateman model, every drug parameter with its clinical source, plus the reconstitution math and titration ladders.
Key Features
- Dose calculations: Models drug levels based on each compound's published half-life data
- Multiple compounds: Track Retatrutide, Semaglutide, and Tirzepatide with compound-specific parameters
- Visual tracking: Interactive graphs show compound levels over time, with peak and trough concentrations
- Stability analysis: See when your compound reaches steady-state levels
- Weight tracking: Log your weight alongside your dosage schedule
- Schedule management: Save and manage multiple dosing schedules with cloud storage
- Calendar view: See daily drug amounts in a calendar format NEW!
- Journal entries: Log notes and side effects alongside your dosage data NEW!
- Share schedules: Share your dosage schedule with a link NEW!
Support Us
If GLP3 Planner has been useful, consider supporting development.
Important Note
GLP3 Planner is an educational tool for visualizing compound pharmacokinetics. It's not medical advice. The calculations use published half-life data and standard PK models, but individual responses vary. Talk to your provider before changing your medication regimen.
GLP-3 Dosing Guide
Retatrutide dosing starts at 2mg weekly and increases every 4 weeks until reaching the 12mg maintenance dose. The full titration takes 16-20 weeks. Each tier needs about 4-5 weeks to reach steady state. Gradual titration matters: clinical trials show significantly fewer GI side effects (nausea, diarrhea) compared to faster escalation. Most people tolerate the lower tiers (2-4mg) well. Side effects tend to show up more at 8mg and above. Use the calculator below to see your drug levels throughout your schedule and when you'll hit steady state at each tier.
Standard Retatrutide Dosage Chart
| Tier | Weekly Dose | Duration |
|---|---|---|
| 1 | 2 mg | 4 weeks |
| 2 | 4 mg | 4 weeks |
| 3 | 6 mg | 4 weeks |
| 4 | 8 mg | 4 weeks |
| 5 | 12 mg | Maintenance |
Note: Individual dosing may vary. Always follow guidance from your healthcare provider.
Get started in seconds with our pre-built titration templates, or build your own custom schedule below.
Dose Schedule
| Week | /Week | Date | Day | Time | Vial | IU | Dose (mg) | Weight (kg) | Journal | Actions |
|---|
Configure Dose Schedule
Quick Start
Select a template to auto-fill the schedule based on your compound