Retatrutide Dosage Chart: Week-by-Week Schedule
The most effective weight loss compound tested in clinical history — 28.7% mean body weight reduction over 68 weeks — and most people can't get the dosing math right on injection day. That's the gap this page closes.
- Starting dose is 2mg/week (Phase 2 protocol) or 0.5mg/week (Phase 3 TRIUMPH protocol) — both are legitimate depending on your starting point and GI sensitivity
- Maximum studied dose is 12mg/week (Phase 2) and 15mg/week (Phase 3 TRIUMPH high arm)
- Every dose increase requires a full 4-week hold — rushing is the #1 cause of early dropouts
- Your syringe draw volume changes at every dose tier depending on how you reconstituted — the tables below remove all guesswork
- Retatrutide outperforms semaglutide and tirzepatide on weight loss endpoints in every head-to-head metric so far
- Missed doses have a specific recovery protocol — it's not just "inject when you remember"
The retatrutide dosage chart is deceptively simple on paper — 2mg, 4mg, 8mg, 12mg, four weeks each. In practice, the math gets messier once you factor in vial concentrations, syringe units, reconstitution volumes, and what happens when you stall at 8mg or have a rough week at 4mg. This page gives you every table you need: week-by-week titration, dose-by-concentration draw volumes, unit conversions, and a head-to-head comparison against semaglutide and tirzepatide. Print it. Bookmark it. Tape it inside your cabinet door.
What Is the Retatrutide Dosage Range?
Retatrutide (LY3437943) is a triple-agonist peptide developed by Eli Lilly. It targets GLP-1, GIP, and glucagon receptors simultaneously — that third receptor (glucagon) is what separates it from tirzepatide and likely explains the additional 4–6% weight loss edge in clinical comparisons.
The dosage range studied in humans:
- Minimum therapeutic dose: 2mg/week (Phase 2) / 0.5mg/week (Phase 3 initiation)
- Common maintenance dose: 8–12mg/week
- Maximum studied dose: 12mg/week (Phase 2) / 15mg/week (Phase 3 TRIUMPH)
- Initiation dose (never skip this): 2mg/week or lower
There is no approved FDA dose yet. Approval is expected in 2027. Everything below reflects Phase 2 and Phase 3 trial protocols and community experience.
Phase 2 vs Phase 3 Protocol: What Changed?
Most dosage charts online only show the Phase 2 protocol. Phase 3 (TRIUMPH) uses a slower start and higher ceiling. Both are worth knowing.
| Parameter | Phase 2 Protocol | Phase 3 TRIUMPH Protocol |
|---|---|---|
| Starting dose | 2mg/week | 0.5mg/week |
| Escalation interval | Every 4 weeks | Every 4 weeks |
| Dose steps | 2 → 4 → 8 → 12mg | 0.5 → 1 → 2 → 3 → 4 → 5 → 8 → 10 → 12 → 15mg |
| Maximum dose | 12mg/week | 15mg/week |
| Duration to max | ~12 weeks | ~36–40 weeks |
| Recommended for | Experienced GLP-1 users | New users, GI-sensitive individuals |
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Honestly, most community protocols split the difference — starting at 1mg and escalating every 4 weeks at a pace somewhere between the two. The key principle is the same regardless: slow escalation dramatically reduces GI side effects.
Retatrutide Week-by-Week Dosage Chart (Weeks 1–24+)
This is the table most people come here for. Two protocols side by side. Use the Phase 2 column if you've used semaglutide or tirzepatide before. Use the TRIUMPH column if this is your first GLP-1 class compound or you're GI-sensitive.
| Week | Phase 2 Dose | TRIUMPH Dose | Phase Name | Expected Effect |
|---|---|---|---|---|
| 1–4 | 2mg | 0.5mg | Initiation | Minimal weight loss; GI adaptation; appetite change by days 2–3 |
| 5–8 | 4mg | 1.0mg | Early escalation | First noticeable appetite suppression; 2–5 lbs typical loss |
| 9–12 | 8mg | 2.0mg | Therapeutic range (P2) / continued escalation (P3) | P2: significant suppression; P3: still building tolerance |
| 13–16 | 12mg (or hold 8) | 3.0mg | Maintenance entry (P2) / mid-escalation (P3) | P2: maximum effect; P3: therapeutic range approaching |
| 17–20 | 12mg | 4.0mg | Maintenance | P3: first real therapeutic dose |
| 21–24 | 12mg | 5.0mg | Maintenance | P3: comparable to P2 week 5–8 effect |
| 25–28 | 12mg or taper | 8.0mg | Maintenance / P3 therapeutic | P3: significant suppression begins |
| 29–32 | — | 10.0mg | P3 high range | Maximum therapeutic benefit for most users |
| 33–36 | — | 12.0mg | P3 advanced | Approaching maximum studied dose |
| 37–40+ | — | 15.0mg | P3 maximum | Only if 10–12mg plateau and tolerated |
When to Pause Escalation
Do not increase your dose if any of these are happening:
- Nausea persisting more than 3 days post-injection
- Vomiting more than twice in a week
- Rapid weight loss above 3–4 lbs/week for 2+ consecutive weeks
- Severe constipation or diarrhea
- Signs of dehydration
Stay at your current dose for an additional 4 weeks. If side effects resolve, escalate. If not, consider dropping back one tier.
Missed Dose Protocol
This is missing from almost every chart online. Here's what the trial data supports:
- Missed dose < 4 days ago: Inject as soon as you remember. Resume your regular weekly day.
- Missed dose 4–7 days ago: Skip the missed dose. Take your next scheduled dose on the regular day.
- Missed dose > 7 days ago: Restart at your previous lower dose tier for 2 weeks before resuming your current dose.
Do not double-dose under any circumstances.
Dose by Vial Concentration: Draw Volume Reference
This is where errors happen. The same 4mg dose requires completely different syringe volumes depending on how you reconstituted your vial. These tables cover the four most common setups. If you're reconstituting differently, use the formula: Volume (mL) = Target Dose (mg) ÷ Concentration (mg/mL).
10mg Vial — Common Reconstitution Options
| Reconstitution | Concentration | 2mg dose | 4mg dose | 8mg dose | 12mg dose |
|---|---|---|---|---|---|
| 10mg + 1mL BW | 10mg/mL | 0.20 mL | 0.40 mL | 0.80 mL | 1.20 mL* |
| 10mg + 2mL BW | 5mg/mL | 0.40 mL | 0.80 mL | 1.60 mL* | 2.40 mL* |
| 10mg + 4mL BW | 2.5mg/mL | 0.80 mL | 1.60 mL* | 3.20 mL* | — |
*Volumes over 1mL may require split injection into two sites. Preferred max single-site volume is 1mL.
5mg Vial — Conservative Start Protocol
| Reconstitution | Concentration | 0.5mg dose | 1mg dose | 2mg dose | 4mg dose |
|---|---|---|---|---|---|
| 5mg + 1mL BW | 5mg/mL | 0.10 mL | 0.20 mL | 0.40 mL | 0.80 mL |
| 5mg + 2mL BW | 2.5mg/mL | 0.20 mL | 0.40 mL | 0.80 mL | 1.60 mL* |
5mg vials are best for the initiation phase if you're going with the TRIUMPH protocol — they'll get you through weeks 1–8 on the 0.5mg/1mg schedule without waste.
Unit Conversion Table: mg → mcg → Insulin Syringe Units
People trip on this constantly. Milligrams, micrograms, and insulin syringe units are three different scales. Here's the complete conversion reference for retatrutide's dosing range.
| Dose (mg) | Dose (mcg) | Volume at 5mg/mL (mL) | U-100 Syringe Units | Volume at 10mg/mL (mL) | U-100 Syringe Units |
|---|---|---|---|---|---|
| 0.5mg | 500mcg | 0.10 mL | 10 units | 0.05 mL | 5 units |
| 1.0mg | 1,000mcg | 0.20 mL | 20 units | 0.10 mL | 10 units |
| 2.0mg | 2,000mcg | 0.40 mL | 40 units | 0.20 mL | 20 units |
| 3.0mg | 3,000mcg | 0.60 mL | 60 units | 0.30 mL | 30 units |
| 4.0mg | 4,000mcg | 0.80 mL | 80 units | 0.40 mL | 40 units |
| 5.0mg | 5,000mcg | 1.00 mL | 100 units | 0.50 mL | 50 units |
| 8.0mg | 8,000mcg | 1.60 mL* | 160 units* | 0.80 mL | 80 units |
| 10.0mg | 10,000mcg | 2.00 mL* | 200 units* | 1.00 mL | 100 units |
| 12.0mg | 12,000mcg | 2.40 mL* | 240 units* | 1.20 mL* | 120 units* |
| 15.0mg | 15,000mcg | 3.00 mL* | 300 units* | 1.50 mL* | 150 units* |
*Split into two injection sites if volume exceeds 1mL.
How to read this: U-100 insulin syringes have markings from 10–100 units, where 100 units = 1.00 mL. A 10mg/mL concentration at 4mg requires 0.40mL = 40 units on the syringe. Simple once you get it. Draw to the 40-unit mark, not 0.40 on the barrel — your syringe probably only shows unit markings, not mL.
Retatrutide vs Semaglutide vs Tirzepatide: Dosage Comparison Chart
People ask this all the time. Here's how the three leading GLP-1 class compounds compare side by side on dosing parameters and clinical outcomes.
| Parameter | Retatrutide | Semaglutide (Ozempic/Wegovy) | Tirzepatide (Mounjaro/Zepbound) |
|---|---|---|---|
| Receptor targets | GLP-1 + GIP + Glucagon | GLP-1 only | GLP-1 + GIP |
| Starting dose | 0.5–2mg/week | 0.25mg/week | 2.5mg/week |
| Maximum studied dose | 15mg/week | 2.4mg/week | 15mg/week |
| Escalation interval | Every 4 weeks | Every 4 weeks | Every 4 weeks |
| Time to max dose | 12–40 weeks | 16 weeks | 20 weeks |
| Half-life | ~6 days | ~7 days | ~5 days |
| Best weight loss (48–68 weeks) | 24.2–28.7% | ~15–17% | ~20–22% |
| FDA approval status | Phase 3 / Expected 2027 | Approved (Wegovy 2.4mg) | Approved (Zepbound 15mg) |
| Route | Subcutaneous injection | Subcutaneous injection | Subcutaneous injection |
| Frequency | Once weekly | Once weekly | Once weekly |
The weight loss edge for retatrutide is real and consistent across trials. About 4–8 percentage points better than tirzepatide, and roughly 10–13 points better than semaglutide. That gap gets even wider at the 68-week mark.
Retatrutide Dosage for Adults: Body Weight Context
Here's something almost no chart addresses: should a 180-pound person and a 350-pound person follow the exact same titration? Honestly, probably not — though the trials didn't stratify dosing by bodyweight in Phase 2.
What the data shows: dose-dependent response is steep. The jump from 4mg to 8mg produces roughly 6–8 additional percentage points of weight loss. The jump from 8mg to 12mg adds another 4–5 points. Staying at 8mg is reasonable if you're already losing 1–2 lbs/week with manageable side effects. See our full retatrutide dosage guide for individualized protocol guidance.
Dose Decision Framework by Response
| Current Dose | Response at Week 4 | Recommendation |
|---|---|---|
| 2mg | Losing <1 lb/week, mild GI | Escalate to 4mg on schedule |
| 2mg | Losing <1 lb/week, severe GI | Hold 4 more weeks at 2mg |
| 4mg | Losing 1–2 lbs/week | Escalate per schedule |
| 4mg | Losing 2+ lbs/week, GI rough | Hold at 4mg — consider 4mg as maintenance |
| 8mg | Weight loss plateau 3+ weeks | Escalate to 12mg |
| 8mg | Losing 1+ lb/week, manageable | Consider 8mg as maintenance — no need to push to 12mg |
| 12mg | Intolerable GI effects | Drop back to 8mg for 4–8 weeks, retry escalation |
GI Side Effect Rates by Dose Tier
This data from Phase 2 trials fills a gap almost no other chart covers. These are approximate rates from the NEJM Phase 2 publication:
| Dose (mg/week) | Nausea (%) | Vomiting (%) | Diarrhea (%) | Constipation (%) |
|---|---|---|---|---|
| 2mg | ~15% | ~5% | ~12% | ~8% |
| 4mg | ~30% | ~10% | ~18% | ~12% |
| 8mg | ~45% | ~20% | ~22% | ~15% |
| 12mg | ~55% | ~25% | ~25% | ~18% |
| Placebo | ~16% | ~4% | ~13% | ~7% |
Key insight: most GI effects are transient. They peak in weeks 1–2 at each new dose tier and typically resolve by week 3–4. Slow titration — not dose reduction — is the primary management tool.
For a detailed breakdown of side effect management strategies, see our retatrutide side effects guide.
How to Inject Retatrutide: Dose Administration Basics
The dosage chart is only useful if the administration is right. Short version:
- Site: Subcutaneous injection — abdomen (2 inches from navel), upper thigh, or outer upper arm
- Rotation: Rotate injection sites weekly to prevent lipodystrophy
- Temperature: Remove from refrigerator 15–20 minutes before injecting
- Pinch: Pinch 1–2 inches of skin, inject at 45–90 degrees
- Day: Same day every week — set a recurring calendar reminder
Full step-by-step injection protocol including reconstitution is covered in our retatrutide injection guide.
Storage and Reconstitution Quick Reference
| Condition | Lyophilized (powder) | Reconstituted (liquid) |
|---|---|---|
| Temperature | Store at room temp or refrigerate | Refrigerate at 2–8°C |
| Shelf life | 12–24 months (sealed) | 28–30 days after reconstitution |
| Light sensitivity | Keep away from direct light | Keep away from direct light |
| Freeze? | Avoid repeated freeze-thaw | Do not freeze |
Retatrutide Dosage Calculator: Manual Method
No interactive tool here — just the math you need to run it yourself:
Formula: Volume (mL) = Target Dose (mg) ÷ Concentration (mg/mL)
Concentration formula: Concentration (mg/mL) = Vial Size (mg) ÷ Bacteriostatic Water Added (mL)
Example: 10mg vial + 2mL bacteriostatic water = 5mg/mL. Target dose = 8mg. Volume = 8 ÷ 5 = 1.6mL. Split into two 0.8mL injections.
U-100 syringe conversion: Units = Volume (mL) × 100
So 0.8mL = 80 units. 0.4mL = 40 units.
Run this calculation before every single injection at a new dose tier. Errors compound across a protocol.
Where to Source Retatrutide
Retatrutide is currently not FDA-approved. Availability is through research supply vendors with third-party lab verification. Always verify:
- HPLC testing certificate (purity ≥98%)
- Certificate of Analysis from independent lab
- Batch-specific documentation
Recommended source: Ascension Peptides — lab-verified supply, ships promptly.
Frequently Asked Questions
The information on this page is based on published Phase 2 and Phase 3 clinical trial data and is provided for educational purposes. Retatrutide is not FDA-approved. Consult a licensed healthcare provider before beginning any peptide protocol. Individual responses to dosing vary significantly.
