Who Is This Protocol For?
- First-time GLP-1 agonist users with no prior semaglutide or tirzepatide experience
- GI-sensitive individuals — history of acid reflux, IBS, or medication-induced nausea
- People who want the lowest possible side-effect burden during initiation
- Anyone with a GLP1R/GIPR gene variant associated with higher nausea risk
Conservative Dosage Chart
| Week | Weekly Dose | Frequency | What to Expect |
|---|---|---|---|
| 1–2 | 0.5 mg | 1× weekly | Mild appetite reduction; minimal side effects |
| 3–4 | 1.0 mg | 1× weekly | Appetite suppression kicks in; some nausea possible |
| 5–8 | 2.0 mg | 1× weekly | Therapeutic threshold; matches Phase 3 starting dose |
| 9–12 | 4.0 mg | 1× weekly | Full effect onset; GIP + GLP-1 receptor engagement |
| 13–16 | 6.0 mg | 1× weekly | Only if tolerating well and plateau detected |
Reta dosing chart: each step lasts at least 4 weeks — the time required for retatrutide to reach ~90% of steady state at each dosage level (based on ~6-day half-life).
Why Start at 0.5 mg Instead of 2 mg?
The Phase 3 TRIUMPH-4 trial started all participants at 2 mg/week. However, community practitioners report that starting at 0.5–1 mg reduces the initiation-phase GI burden significantly. The tradeoff: therapeutic appetite suppression takes 2–4 weeks longer to appear.
At 0.5 mg, steady-state Cmax ≈ 0.9 mg equivalent — well below the GI threshold for most users. At 2 mg, steady-state Cmax ≈ 3.7 mg equivalent — above the nausea threshold for approximately 30% of trial participants.
With a ~6-day half-life, 5 half-lives (30 days ≈ 4 weeks) reaches ~97% of steady state. Starting at 0.5 mg means your peak exposure during weeks 1–4 is roughly 0.9 mg equivalent — low enough that most users experience little to no GI disruption. This builds tolerance before escalating to therapeutic levels.
How to Take This Protocol
Reta is injected subcutaneously (under the skin) once per week, on the same day each week. Common injection sites are the abdomen, thigh, or upper arm. Rotate sites to avoid irritation. Inject at any time of day — consistency matters more than timing. Many reta users find that injecting in the evening reduces next-day nausea, though this varies by individual.
Companion Requirements
- Protein: 1 g per pound of lean body mass/day minimum. Leucine-rich sources support mTOR activation.
- Calorie floor: 1,500 cal/day regardless of appetite. Set alarms to eat if needed.
- Resistance training: 3×/week minimum. Bodyweight exercises count. Maintain intensity.
- Carbohydrates: Moderate intake; avoid keto. Retatrutide's glucagon component benefits from mixed-nutrient meals.
Monitoring Schedule
| Metric | Frequency | Why |
|---|---|---|
| Resting heart rate | Daily | RHR can increase 7–10 bpm at higher doses |
| Blood pressure | Weekly | Cardiovascular baseline + tracking |
| Blood work | Baseline + 8 wk | Fasting glucose, A1C, liver enzymes, lipids |
| Hormone panel | Baseline + 12 wk | Total/free T, estradiol, SHBG |
| Body weight | Weekly | Same conditions; track trend, not daily swings |
When to Hold Escalation
Do not escalate to the next dose level if:
- GI symptoms rate ≥ 3/10 severity for more than 3 days at current dose
- You have not completed at least 4 full weeks at the current dose
- Resting heart rate has increased more than 15 bpm from baseline
- Caloric intake has dropped below 1,200 cal/day due to appetite suppression
Hold at the current dose for an additional 2–4 weeks. If symptoms persist beyond 8 weeks at any single dose level, consult your prescribing provider.
Never stop retatrutide abruptly. Taper over 4–6 weeks: reduce to 50% for 2 weeks, then 25% for 2 weeks, while increasing calories by 200–300/day before the last full dose. BMJ data shows 4 kg/month regain without a structured exit protocol.
Compare Starting Protocols
- Standard Protocol — 2 mg start, matches TRIUMPH-4 trial
- Split Dose Protocol — divide weekly dose across 2 injections