Feature-by-Feature Comparison
Retatrutide is a triple-agonist GLP-1 medication with a half-life of 144–165 hours (Coskun et al. 2022). Dose stacking over weekly injections is significant, and most trackers have no mechanism to model it.
| Feature | Retadose | Shotsy | GLP1Plotter | DoseDiary |
|---|---|---|---|---|
| PK-based level modeling | ✅ 1-compartment model | ❌ | ⚠️ Generic curves | ❌ |
| Retatrutide-specific | ✅ Purpose-built | ⚠️ Afterthought | ⚠️ Generic GLP-1 | ⚠️ Generic logger |
| Dose stacking visualization | ✅ Real-time curve | ❌ | ⚠️ Partial | ❌ |
| Suggested next dose | ✅ PK-based | ❌ | ❌ | ❌ |
| Therapeutic window targeting | ✅ Mark your level | ❌ | ❌ | ❌ |
| Symptom check-ins | ✅ Linked to PK level | ✅ Basic logging | ❌ | ✅ Basic logging |
| Data export | ✅ Full history + PK | ✅ PDF export | ❌ | ❌ |
| Price | Free | Freemium ($8/mo) | Free | Free |
| Platform | PWA (any browser) | iOS + Android | Web | iOS + Android |
| PK parameters source | Coskun 2022 | N/A | Not cited | N/A |
Why PK Modeling Matters for Retatrutide
Retatrutide's 6-day half-life means each dose stacks on top of prior doses that are still partially active. After 3–4 weekly injections, your trough concentration is nearly double what a single dose produces. This accumulation is invisible without pharmacokinetic modeling.
A simple injection logger cannot tell you:
- What your estimated drug level is right now
- Whether your level has overshot your therapeutic window
- What dose to take next to return to your target range
Retadose calculates all three using the elimination rate constant (ke ≈ 0.00471/h), absorption rate constant (ka ≈ 0.065/h), and volume of distribution (Vz/F ≈ 8.3 L) from published phase 1 PK data (Coskun et al. 2022).
Shotsy is the leading GLP-1 tracker with ~70,000+ users and apps on iOS and Android. They added retatrutide support in 2026, but their architecture is an injection logger with reminder scheduling — not a pharmacokinetic modeler. For approved GLP-1 medications like Mounjaro and Zepbound, Shotsy is excellent. For retatrutide-specific PK tracking, Retadose is the purpose-built tool.
When to Use What
Use Retadose if: You are on retatrutide (compounded or clinical trial) and want to understand your actual drug level, find your personal therapeutic window, and get data-driven dose suggestions.
Use Shotsy if: You are on an approved GLP-1 medication (Mounjaro, Zepbound, Wegovy, Ozempic) and primarily need injection site rotation tracking and habit logging.
Use GLP1Plotter if: You want a quick visual estimate of generic GLP-1 concentration curves without account creation.