Who Is This Protocol For?
- Users who get GI side effects on injection day or the day after — peak-related nausea, not sustained
- People who want the smoothest possible plasma curve — reducing Cmax spikes
- Anyone already on a stable dose wanting to explore splitting for comfort
- Users willing to inject 2× per week instead of once
Split Dose Dosage Chart
| Week | Weekly Total | Split As | Example Days | Notes |
|---|---|---|---|---|
| 1–2 | 0.5 mg | 0.25 mg × 2 | Wed / Sun | Ultra-conservative start |
| 3–4 | 1.0 mg | 0.5 mg × 2 | Wed / Sun | Appetite suppression begins |
| 5–8 | 2.0 mg | 1.0 mg × 2 | Wed / Sun | Therapeutic threshold |
| 9–12 | 4.0 mg | 2.0 mg × 2 | Wed / Sun | Full effect; evaluate at 12 wk |
| 13+ | 6.0 mg | 3.0 mg × 2 | Wed / Sun | Only if plateau detected |
Reta dosing chart: each step lasts at least 4 weeks. Weekly totals match the conservative protocol — only the delivery pattern changes.
How Splitting Reduces Side Effects
With a ~6-day half-life, splitting a weekly dose into two injections 3–4 days apart produces lower peak concentration (each injection is half the dose), more stable trough levels (less "valley" on days 5–7), and essentially the same total weekly drug exposure. You're not using less drug — just distributing it more evenly.
This is the same principle used in testosterone replacement therapy, where splitting weekly injections into twice-weekly reduces estradiol spikes and improves hormonal stability. For retatrutide, the benefit is a smoother GLP-1/GIP/glucagon activation curve with fewer acute GI events on injection day.
Choosing Injection Days
The ideal split puts 3–4 days between injections:
| Pattern | Days Between |
|---|---|
| Monday / Thursday | 3 and 4 days |
| Tuesday / Friday | 3 and 4 days |
| Wednesday / Sunday | 4 and 3 days |
| Monday / Friday | 4 and 3 days |
Retadose supports arbitrary injection-day selection. Set your dose days in Settings and the PK model computes your concentration curve using the actual timing of each injection.
How to Take a Split Dose
Each reta injection is subcutaneous — under the skin, same technique as once-weekly. The only difference: you inject twice per week at half the dosage each time. Use separate injection sites for each dose (e.g., left abdomen Wednesday, right abdomen Sunday). Consistent timing matters most — set reminders for both dose days.
Switching from Single to Split Dosing
- Wait until your next scheduled injection day
- Inject half your current weekly dose
- 3–4 days later, inject the other half
- Continue on the split pattern going forward
No washout period is needed. The total weekly dose stays the same — only the delivery pattern changes. Your PK curve in Retadose will update automatically when you log the split doses.
Companion Requirements
- Protein: 1 g per pound of lean body mass/day minimum.
- Calorie floor: 1,500 cal/day regardless of appetite.
- Resistance training: 3×/week minimum. Maintain intensity.
- Carbohydrates: Moderate intake; avoid keto. Glucagon activation benefits from mixed-nutrient meals.
Split dosing reduces peak-related side effects. It does not help with sustained nausea lasting 3+ days (a total-dose problem), appetite suppression that's too strong (same AUC regardless of split), or injection site reactions (more injection events may worsen site discomfort).
Compare Starting Protocols
- Conservative Protocol — 0.5 mg start, once-weekly, slowest titration
- Standard Protocol — 2 mg start, matches TRIUMPH-4 trial