Retatrutide Dosage Chart: Week-by-Week Guide for Every Phase
The definitive retatrutide dosage chart — phase-by-phase escalation schedule from starter doses to 12 mg, with beginner, standard, and aggressive protocols.
If you've seen retatrutide's headline numbers — up to 24.2% body weight reduction in 48 weeks in a Phase 2 clinical trial — you're probably wondering one thing: exactly how do I dose it? The existing retatrutide content online describes the drug without giving you what you actually need: a clear, visual dosage chart showing how to escalate through each phase, week by week. This guide fixes that.
Whether you're a complete beginner nervous about side effects or an experienced researcher ready to push toward the 12 mg maintenance dose, the phase-by-phase retatrutide dosage chart below gives you a concrete roadmap. We'll also cover what to expect at each dose level, how to manage GI side effects during escalation, and answers to the most common dosing questions.
What Is Retatrutide? (Quick Recap)
Retatrutide (LY3437943) is Eli Lilly's investigational triple receptor agonist — simultaneously activating GLP-1, GIP, and glucagon receptors. This triple mechanism is what distinguishes it from semaglutide (GLP-1 only) and tirzepatide (GLP-1 + GIP): the addition of glucagon receptor agonism increases energy expenditure while GLP-1 suppresses appetite and GIP improves metabolic efficiency.
In the landmark Phase 2 trial published in the New England Journal of Medicine (Jastreboff et al., 2023), participants receiving 12 mg weekly lost an average of 24.2% of their body weight over 48 weeks — surpassing every previously approved weight loss medication at time of publication. Phase 3 trials (the TRIUMPH program) are ongoing.
Key Retatrutide Phase 2 Trial Data (NEJM, 2023)
Four retatrutide doses were tested via weekly subcutaneous injection over 48 weeks against placebo. Results: 1 mg → 8.7% weight loss | 4 mg → 17.1% weight loss | 8 mg → 22.8% weight loss | 12 mg → 24.2% weight loss. Placebo group: -1.6%. All active doses significantly outperformed placebo.
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Ascension PeptidesWhy Dose Escalation Is Non-Negotiable
Retatrutide works on three receptor systems simultaneously, which means the side effect profile — primarily gastrointestinal — can be more pronounced than with single-agonist drugs if you ramp up too quickly. Nausea, vomiting, and diarrhea are the most common adverse events, and they're almost entirely dose-dependent and tied to escalation speed.
The clinical trial used a structured 4-week hold between dose levels specifically to allow GI tolerance to develop. Compressing the escalation schedule is the single most common mistake researchers make — it's the primary driver of discontinuing what would otherwise be an effective protocol. Slow escalation isn't weakness; it's strategy.
The Escalation Principle
Your GI tract needs time to adapt to incremental GLP-1 receptor stimulation. Rushing escalation doesn't make retatrutide work faster — it increases the likelihood of side effects that force a dose reduction anyway. Slow and steady consistently wins with triple agonists.
The Retatrutide Dosage Chart: All Three Protocols
The table below is the retatrutide dosage chart you've been looking for — a week-by-week breakdown for three protocols: Beginner (ultra-conservative, ideal for those new to GLP-1 class drugs), Standard (mirrors the Phase 2 trial escalation schedule), and Aggressive (faster ramp for experienced researchers with prior GLP-1 exposure).
All doses are administered as a once-weekly subcutaneous injection. Escalation intervals are 4 weeks minimum at each dose level before stepping up.
| Weeks | 🟢 Beginner | 🔵 Standard | 🔴 Aggressive | Phase |
|---|---|---|---|---|
| Weeks 1–4 | 0.5 mg | 2 mg | 2 mg | Induction |
| Weeks 5–8 | 1 mg | 4 mg | 4 mg | Early Escalation |
| Weeks 9–12 | 2 mg | 6 mg | 8 mg | Mid Escalation |
| Weeks 13–16 | 4 mg | 8 mg | 12 mg | Upper Escalation |
| Weeks 17–20 | 6 mg | 10 mg | 12 mg | Pre-Maintenance |
| Weeks 21–24 | 8 mg | 12 mg | 12 mg | Maintenance |
| Weeks 25+ | 8–12 mg | 12 mg | 12 mg | Long-Term Maintenance |
Not Sure Which Dose Is Right for You?
Our AI Peptide Coach calculates your ideal starting dose and week-by-week escalation schedule based on your weight, age, goals, and health history — and tracks your progress over time and helps dealing with possible side effects.
→ Get My Personalized Dosage PlanAll doses are once-weekly subcutaneous injections. 12 mg represents the highest dose studied in Phase 2 clinical trials. This chart is for informational and research purposes only — not medical advice.
Protocol Breakdown: Which One Is Right for You?
🟢 Beginner Protocol (Ultra-Conservative)
Best for: First-time GLP-1 users, individuals with a history of severe nausea on other weight loss medications, or anyone who wants to prioritize GI tolerance over speed of escalation.
The beginner protocol starts at 0.5 mg — half the lowest dose tested in clinical trials. The tradeoff is a longer runway to reach maintenance dose (approximately 20–28 weeks to reach 8–12 mg), but significantly lower risk of GI disruption. If you've never used semaglutide, tirzepatide, or any other GLP-1 agonist before, starting here is a sound approach. You can always escalate faster if you find your tolerance is good.
🔵 Standard Protocol (Trial-Matched)
Best for: Most researchers. Especially those with moderate GI tolerance or prior experience with GLP-1 agonists (semaglutide, tirzepatide, or liraglutide).
The standard protocol mirrors the escalation schedule used in the Phase 2 clinical trial: starting at 2 mg for 4 weeks, then stepping up in increments every 4 weeks toward 12 mg. This is the best-evidenced approach — the trial's safety and efficacy data were generated with exactly this schedule. If you've tolerated semaglutide or tirzepatide without major issues in the past, this is your default protocol.
🔴 Aggressive Protocol (Experienced Researchers Only)
Best for: Individuals with high GI tolerance who have previously completed a full cycle of a GLP-1 agonist at maximum dose without significant adverse events.
The aggressive protocol compresses the escalation to reach 12 mg by weeks 13–16. This carries a higher risk of GI side effects and is not recommended for beginners. If nausea or vomiting becomes unmanageable, drop back to the previous dose and hold for an additional 2–4 weeks before attempting to escalate again. Pushing through significant GI distress is counterproductive — it leads to dehydration, electrolyte imbalance, and often protocol abandonment.
What to Expect at Each Retatrutide Dose Level
Understanding what each dose level typically delivers helps calibrate expectations — and helps you decide whether to hold at a dose plateau or continue escalating.
1–2 mg Weekly (Induction Phase)
Appetite suppression begins to emerge, particularly in the evening. Most researchers notice they're reaching for less food without consciously trying. GI effects (mild nausea, occasional loose stools) are usually well-managed at this level. Expect 2–5% weight loss over the first 4–8 weeks. The glucagon receptor component begins contributing to increased energy expenditure, though its effects are more pronounced at higher doses.
4–6 mg Weekly (Early Escalation)
Appetite suppression becomes pronounced — many researchers report naturally eating 30–50% less without conscious caloric restriction. This is often described as the sweet spot for tolerability vs. efficacy. The 4 mg dose group in the Phase 2 trial produced an average 17.1% weight loss by week 48. GI adaptation is largely complete for most people by the time they reach this range, and side effects — if they occurred during escalation — typically diminish significantly.
8 mg Weekly (Upper Escalation)
The 8 mg dose group achieved 22.8% weight loss at 48 weeks in the Phase 2 trial. At this level, many researchers report near-complete appetite suppression — extended periods without hunger signals. Attention to adequate protein intake becomes critical at this stage, as dramatically reduced caloric consumption can lead to lean muscle loss if protein targets aren't maintained (aim for 0.7–1g per pound of bodyweight). GI side effects, if present, typically peak during the first 2 weeks after dose escalation to 8 mg.
12 mg Weekly (Maximum Studied Dose)
The highest dose tested in Phase 2 trials produced 24.2% average weight loss at 48 weeks — only about 1.4 percentage points more than the 8 mg group, but significant given the baseline. At 12 mg, caloric restriction becomes almost effortless for most researchers. The glucagon agonist component contributes meaningfully to adipose tissue mobilization at this dose. Not everyone needs to reach 12 mg: given the diminishing returns above 8 mg, many researchers choose to maintain at 8 mg as their maximum dose.
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Ascension PeptidesHow to Administer Retatrutide
Retatrutide is administered as a once-weekly subcutaneous (under-the-skin) injection. Proper technique minimizes discomfort and ensures consistent absorption:
- Injection sites: Rotate between abdomen (at least 2 inches from navel), front of thigh, and outer upper arm. Rotating sites weekly prevents lipodystrophy and injection site reactions.
- Technique: Pinch the skin, insert the needle at a 45–90 degree angle (45 degrees for leaner individuals, 90 degrees if more subcutaneous fat is present). Inject slowly and hold for 5 seconds before withdrawing.
- Consistency: Choose a fixed day of the week (e.g., every Monday) and stick to it. Retatrutide has a half-life of approximately 6 days, so weekly dosing maintains stable plasma levels.
- Storage: Refrigerate at 36–46°F (2–8°C). May be kept at room temperature (up to 77°F/25°C) for up to 28 days once removed from the fridge. Never freeze. Protect from light.
- Meal timing: Can be injected at any time of day, with or without food. Some researchers prefer evening injection, reporting that any mild nausea peaks overnight while they sleep.
- Missed dose: If less than 4 days late, inject as soon as you remember. If 4+ days have passed, skip the missed dose and resume on your next scheduled injection day. Never double dose.
Managing Side Effects During Escalation
The most common retatrutide side effects are gastrointestinal and are almost entirely related to escalation speed and individual GI sensitivity. Good news: they're predictable and manageable with the right approach.
The GI Management Toolkit
These strategies significantly reduce GI side effects during escalation phases: (1) Smaller, more frequent meals — avoid large meals, especially within 2 hours of injection. (2) Low-fat foods for 48 hours post-injection — fatty meals amplify nausea. (3) Ginger tea or supplements — well-evidenced for nausea reduction. (4) Stay hydrated — diarrhea risk compounds with dehydration. (5) Consider evening injections — many find peak nausea occurs overnight. (6) If vomiting occurs more than once per week: hold your current dose for an additional 2–4 weeks before escalating.
GI side effects with retatrutide follow a predictable arc. They typically peak during the first 1–2 weeks at a new dose level, then diminish significantly as your GI system adapts. Most researchers report that by week 3–4 at a new dose, GI effects are minimal to absent. If you experience persistent vomiting, severe abdominal pain, or signs of pancreatitis (persistent upper abdominal pain radiating to the back), discontinue use and seek medical evaluation immediately.
Retatrutide Dosing: Key Principles at a Glance
- Always start at the lowest dose appropriate for your experience level — never start at maintenance
- Maintain each dose level for a minimum of 4 weeks before escalating
- If side effects are significant, hold at the current dose for an additional 2–4 weeks before attempting to escalate
- The 8 mg dose provides the best efficacy-to-tolerability ratio for most researchers based on Phase 2 data
- 12 mg is the highest dose with clinical evidence — going above this has no data backing and is not recommended
- Track body weight, food intake, and side effects weekly — data helps you make informed escalation decisions
- Prioritize protein intake (0.7–1g per pound of bodyweight) during rapid weight loss to preserve lean muscle mass
- At higher doses (8–12 mg), supplement with a quality multivitamin and electrolytes given dramatically reduced caloric intake
- Do not combine with other GLP-1 agonists (semaglutide, tirzepatide) — there is no evidence this is safe or beneficial
Frequently Asked Questions
What is the recommended starting dose for retatrutide?
The Phase 2 clinical trial used 2 mg as the minimum starting dose for all active treatment groups. In practice, researchers new to GLP-1 agonists often start at 0.5–1 mg weekly for 4 weeks to assess GI tolerance before stepping up to 2 mg. If you have prior GLP-1 experience with no major side effects, starting at 2 mg (the standard protocol) is appropriate.
How long does it take to reach the maximum retatrutide dose?
On the standard protocol, reaching 12 mg takes approximately 20–24 weeks (five or six 4-week escalation steps). On the aggressive protocol, some researchers reach 12 mg in 12–16 weeks. The beginner protocol may take 24–32 weeks to reach a comparable maintenance dose. Remember: reaching maintenance faster doesn't translate to faster fat loss — the body adapts to each dose level regardless of how quickly you escalate.
Can I maintain at a lower dose (4–8 mg) rather than pushing to 12 mg?
Absolutely — and this is often the right call. The 4 mg group lost an average of 17.1% body weight, and the 8 mg group lost 22.8% in the Phase 2 trial. These are exceptional outcomes in their own right. The jump from 8 mg to 12 mg added roughly 1.4 percentage points of additional weight loss on average, which may not justify a meaningfully higher side effect burden for everyone. If you're achieving your goals and tolerating a given dose well, there is no clinical mandate to escalate further.
How do I calculate the injection volume from a retatrutide vial?
The injection volume depends on your vial concentration. For example, if your vial is 10 mg/mL and your weekly dose is 4 mg, you would inject 0.4 mL (400 microliters). If your vial is 5 mg/mL and your dose is 4 mg, you would inject 0.8 mL (800 microliters). Always verify the concentration printed on the vial label and calculate carefully before drawing up. Using an insulin syringe calibrated in units can make small volumes easier to measure accurately.
How does retatrutide dosing compare to semaglutide (Ozempic/Wegovy) or tirzepatide (Mounjaro/Zepbound)?
All three are once-weekly subcutaneous injections with similar escalation logic. However, the numeric doses differ: semaglutide tops out at 2.4 mg/week for obesity (Wegovy), tirzepatide peaks at 15 mg/week (Zepbound), and retatrutide was studied up to 12 mg/week. These numbers aren't directly comparable because each molecule has different potency per milligram — the clinical outcomes data (weight loss %) is the better basis for comparison. In head-to-head terms, retatrutide's 24.2% weight loss at 48 weeks in Phase 2 exceeds semaglutide's ~14.9% (STEP 1 trial at 72 weeks) and tirzepatide's ~22.5% (SURMOUNT-1 at 72 weeks), though longer-duration Phase 3 data for retatrutide is still pending.
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