Retatrutide dosage schedule (Phase 2 titration)
The titration below mirrors the TRIUMPH-1 protocol. It starts low to allow the GI tract and hypothalamic appetite circuits to adapt, then escalates every four weeks to the target maintenance dose.
| Weeks | Dose | Rationale |
|---|---|---|
| 1–4 | 0.5 mg | Starter — minimize GI side effects |
| 5–8 | 1 mg | First escalation |
| 9–12 | 2 mg | Tolerability checkpoint |
| 13–16 | 4 mg | Intermediate dose |
| 17–20 | 8 mg | Pre-maintenance |
| 21+ | 12 mg | Maintenance target (highest Phase 2 arm) |
Most peptide-community users stop escalating at 4–8 mg — enough to produce substantial weight loss (17–23% at 48 weeks) while keeping nausea, fatigue, and other GI side effects more manageable than on 12 mg. There is no pharmacology reason 12 mg is "correct"; it's simply the highest dose tested in Phase 2.
Retatrutide dosage chart: mg to units, 10 mg vial
A 10 mg vial reconstituted with 1 mL of bacteriostatic water yields a concentration of 10 mg/mL. At that concentration, on a U-100 insulin syringe:
| Dose (mg) | Volume (mL) | Units (U-100) |
|---|---|---|
| 0.5 mg | 0.05 mL | 5 units |
| 1 mg | 0.10 mL | 10 units |
| 2 mg | 0.20 mL | 20 units |
| 4 mg | 0.40 mL | 40 units |
| 8 mg | 0.80 mL | 80 units |
| 12 mg | 1.20 mL | 120 units (exceeds barrel — split dose) |
For 12 mg on a single U-100 syringe, reconstitute with 2 mL BAC water instead: concentration becomes 5 mg/mL, 12 mg = 2.4 mL... still exceeds barrel. Practical solution: use a 20 mg vial plus 2 mL water (10 mg/mL concentration, 12 mg = 1.2 mL — also over) or 20 mg + 1 mL water (20 mg/mL, 12 mg = 0.6 mL = 60 units — fits). Our calculator handles these combinations.
How to take retatrutide (injection technique)
- Pick an injection site. Abdomen (2+ inches from navel), front of thigh, or back of upper arm. Rotate sites weekly to prevent lipohypertrophy.
- Let the vial come to room temperature. Cold injections hurt more. 15–30 minutes out of the fridge is enough.
- Sterilize. Alcohol swab the vial stopper. Then alcohol swab the injection site and let it air dry (injecting into wet alcohol stings).
- Draw your dose. Use the calculator above. Pull air into the syringe first equal to your draw volume, inject that into the vial (avoids negative pressure), then invert and draw. Flick to remove bubbles.
- Inject subcutaneously. Pinch skin, insert needle at 45–90°, depress plunger slowly over 3–5 seconds, hold for 3 seconds, withdraw.
- Record it. Note dose, site, and any side effects. Weekly consistency matters.
Detailed technique, site rotation diagrams, and common mistakes on the injection guide.
Retatrutide dosing for weight loss vs bodybuilding
For weight loss, the trial-backed approach is titrating to 4, 8, or 12 mg over 4–5 months and holding for at least 48 weeks. Weight loss in TRIUMPH-1 had not plateaued at 48 weeks, so longer duration likely produces additional loss.
For "retatrutide bodybuilding" dosage, there is no clinical evidence. Peptide communities typically use 1–4 mg weekly, cycling on for 12–24 weeks and off for a recovery period. The logic is to exploit the appetite suppression and fat-oxidation effects during a cutting phase without the aggressive weight loss (and associated muscle loss) that comes from higher doses. This use is unstudied.
Retatrutide dosing in units: quick reference
When a trial protocol or online forum says "10 mg/mL" or "5 mg/mL," it's referring to the reconstituted vial's concentration. Always check concentration before drawing. Units drawn = (desired mg) × (100 units/mL) / (concentration mg/mL).
| Concentration | For 2 mg dose | For 4 mg dose | For 8 mg dose |
|---|---|---|---|
| 10 mg/mL | 20 units | 40 units | 80 units |
| 5 mg/mL | 40 units | 80 units | 160 units (2× injection) |
| 3.3 mg/mL | 60 units | 120 units (over barrel) | Split dose |
| 20 mg/mL | 10 units | 20 units | 40 units |
Retatrutide dosage for weight loss: which target?
Phase 2 gave us four data points:
For most goals, 4–8 mg is a reasonable target. The marginal weight loss from 8 → 12 mg was 1.4 percentage points, while GI side effect rates rose materially. If you tolerate 8 mg well and weight loss is stalled after 6 months, stepping to 12 mg may be worth discussing with a prescribing physician. If 8 mg gives you 20% loss and you're happy, stopping there is defensible.
Retatrutide half-life and timing
Retatrutide has an approximate half-life of 160 hours (6.7 days), which is why once-weekly dosing produces stable serum levels. Peak concentration occurs ~48 hours post-injection; trough is right before the next dose. If you skip a week, the following-week dose is unchanged; if you skip multiple weeks, re-starting at a lower rung of the titration ladder is prudent to minimize GI side effects.
Best time of day to take retatrutide: whenever is consistent. Side effects often peak 24–48 hours post-injection, so many users inject in the evening before an off day to sleep through the worst.
Retatrutide dosing reddit consensus
The Reddit peptide community — r/Peptides and related subs — converges on a few patterns around retatrutide dosing:
- Slow escalation beats fast escalation. Holding each rung for 4–6 weeks instead of 4 reduces nausea substantially.
- 4–6 mg is the "sweet spot" for most. Users report comparable weight loss to 8 mg with noticeably less GI load.
- Microdoses (0.25–0.75 mg) produce weak but real effects. Insufficient for significant weight loss, but appetite reduction is reported.
- Consistent injection day matters. Skipping weeks or switching injection day leads to rebound appetite spikes.
As always, Reddit is not pharmacology. These are self-reported patterns from self-experimenters, not clinical evidence.