Retatrutide dosage chart: weekly titration schedule

Retatrutide is Eli Lilly’s investigational triple-receptor agonist currently in Phase 3 clinical trials. The dosing protocols tested so far follow a gradual titration schedule, starting low and increasing every four weeks to reduce gastrointestinal side effects. This page covers every dosing detail from the published Phase 2 trial and the Phase 3 TRIUMPH program.

One thing to be upfront about: there is no FDA-approved dose of retatrutide because the drug is not yet approved. Everything below comes from clinical trial protocols. Your prescribing provider will determine the right dose for your situation if and when retatrutide becomes available. For current weight loss peptide options that are available today, see our guide.

Key takeaways

• Retatrutide is dosed once weekly by subcutaneous injection
• The Phase 2 trial tested doses of 1 mg, 4 mg, 8 mg, and 12 mg
• Standard titration starts at 2 mg and increases every 4 weeks: 2 mg, 4 mg, 8 mg, then 12 mg
• Phase 3 trials test 9 mg and 12 mg as target maintenance doses, with a 4 mg maintenance option
• Higher doses produced greater weight loss but also more side effects
• The half-life is approximately 6 days, supporting once-weekly dosing

Phase 2 trial dosing protocol

The Phase 2 trial published in the New England Journal of Medicine enrolled 338 adults and tested multiple dose levels over 48 weeks [1]. Here is how the dosing groups were structured:

Dose group	Starting dose	Titration	Target dose	Duration
1 mg	1 mg	No titration	1 mg	48 weeks
4 mg (slow)	2 mg x 4 weeks	4 mg at week 5	4 mg	48 weeks
4 mg (fast)	4 mg	No titration	4 mg	48 weeks
8 mg (slow)	2 mg x 4 weeks, 4 mg x 4 weeks	8 mg at week 9	8 mg	48 weeks
8 mg (fast)	4 mg x 4 weeks	8 mg at week 5	8 mg	48 weeks
12 mg	2 mg x 4 weeks, 4 mg x 4 weeks, 8 mg x 4 weeks	12 mg at week 13	12 mg	48 weeks

The slow titration groups experienced fewer gastrointestinal side effects during the dose-escalation period compared to fast titration groups [1]. This is why gradual escalation became the standard approach in Phase 3.

Standard titration chart (12 mg target)

Based on the clinical trial protocols, the standard titration for retatrutide follows a 4-week step-up pattern. This was the schedule used for the 12 mg group in Phase 2 and the basis for Phase 3 dosing [1][2]:

Week	Dose	Injection volume*	Notes
Week 1	2 mg	Varies by concentration	Starting dose
Week 2	2 mg	Varies by concentration	Maintain starting dose
Week 3	2 mg	Varies by concentration	Maintain starting dose
Week 4	2 mg	Varies by concentration	Last week at 2 mg
Week 5	4 mg	Varies by concentration	First dose increase
Week 6	4 mg	Varies by concentration	Maintain
Week 7	4 mg	Varies by concentration	Maintain
Week 8	4 mg	Varies by concentration	Last week at 4 mg
Week 9	8 mg	Varies by concentration	Second dose increase
Week 10	8 mg	Varies by concentration	Maintain
Week 11	8 mg	Varies by concentration	Maintain
Week 12	8 mg	Varies by concentration	Last week at 8 mg
Week 13+	12 mg	Varies by concentration	Target maintenance dose

*Injection volumes depend on the concentration of the reconstituted or prefilled product. Clinical trials used prefilled pens, but compounded versions will vary. See our guide on how to reconstitute retatrutide for preparation details.

Phase 3 TRIUMPH dosing

The Phase 3 TRIUMPH program modified the dosing approach based on Phase 2 findings. TRIUMPH-4, the first completed Phase 3 trial, tested two dose levels against placebo [2]:

Treatment arm	Titration schedule	Target dose
Retatrutide 9 mg	Gradual escalation over 20 weeks	9 mg weekly
Retatrutide 12 mg	Gradual escalation over 24 weeks	12 mg weekly
Placebo	N/A	N/A

The titration in Phase 3 was slower than Phase 2. Participants escalated in smaller increments over 20 to 24 weeks before reaching their target dose. Lilly also introduced a 4 mg maintenance dose in other TRIUMPH trials, designed for patients who achieve their weight loss goal and want to maintain results at a lower dose [2].

Weight loss by dose level

The dose you take directly correlates with how much weight you lose. Here is what the trials showed:

Phase 2 results at 48 weeks [1]

Dose	Mean weight loss (%)	Mean weight loss (lbs)
Placebo	-2.1%	~5 lbs
1 mg	-8.7%	~19 lbs
4 mg (combined)	-17.1%	~38 lbs
8 mg (combined)	-22.8%	~51 lbs
12 mg	-24.2%	-57.8 lbs

Phase 3 TRIUMPH-4 results at 68 weeks [2]

Dose	Mean weight loss (%)	Mean weight loss (lbs)
Placebo	-2.1%	-4.6 lbs
9 mg	-26.4%	-64.2 lbs
12 mg	-28.7%	-71.2 lbs

The Phase 3 numbers are higher partly because the trial ran 20 weeks longer (68 vs 48 weeks) and partly because the study population had a higher average BMI of 40.4 kg/m² [2].

Side effects at each dose level

Higher doses mean more weight loss but also more side effects. The gastrointestinal effects are dose-dependent and most common during the titration phase when doses increase [2]:

Side effect	9 mg	12 mg	Placebo
Nausea	38.1%	43.2%	10.7%
Diarrhea	34.7%	33.1%	13.4%
Constipation	21.8%	25.0%	8.7%
Vomiting	20.4%	20.9%	0.0%
Decreased appetite	19.0%	18.2%	9.4%
Dysesthesia	8.8%	20.9%	0.7%

Data from TRIUMPH-4, 68 weeks [2]. Dysesthesia (tingling or abnormal skin sensations) was a notably higher finding at the 12 mg dose compared to lower doses, though these events were generally mild.

Discontinuation due to adverse events was 12.2% at 9 mg and 18.2% at 12 mg, compared to 4.0% on placebo [2]. For patients with a baseline BMI of 35 or higher, discontinuation rates were lower: 8.8% (9 mg) and 12.1% (12 mg) [2].

How to time your weekly injection

Retatrutide has a half-life of approximately 144 hours, or about 6 days [3]. This supports once-weekly dosing and means blood levels stay relatively stable throughout the week. Pick the same day each week for your injection. If you miss your scheduled day by a day or two, take it when you remember and resume your normal schedule the following week.

Most patients inject in the morning, but there is no clinical data suggesting one time of day is better than another. Choose whatever time you will consistently remember. If you are new to self-injection, our guide to peptide injections covers technique, injection site rotation, and common mistakes.

Common subcutaneous injection sites include the abdomen (at least 2 inches from the navel), outer thigh, and back of the upper arm. Rotate between sites weekly to reduce the chance of injection-site reactions. For more detail on injection locations, see our peptide injection sites guide.

Adjusting your dose

In clinical trials, doses were not adjusted downward based on side effects. Participants either continued escalating on schedule or stayed at their current dose longer before increasing. In clinical practice, your provider may take a different approach.

If you experience significant nausea or GI side effects at a new dose level, holding at that dose for an extra 2 to 4 weeks before increasing is reasonable. Some practitioners use the 8 mg dose as a long-term maintenance dose rather than pushing to 12 mg, especially for patients who reach their target weight or cannot tolerate higher doses.

The Phase 3 TRIUMPH program also tested a 4 mg maintenance dose specifically for patients who reach their goal and want to maintain weight loss without the side effect burden of higher doses [2]. Results from that arm of the trials are expected in 2026.

What to expect at each dose level

Understanding what happens at each stage of the titration helps set realistic expectations.

Weeks 1-4 (2 mg): Most patients feel minimal effects at the starting dose. Appetite suppression is mild if noticeable at all. Nausea is uncommon. This phase is about getting your body accustomed to the drug before escalating. Weight loss during this period is typically modest, around 2-3% of body weight based on Phase 2 data [1].

Weeks 5-8 (4 mg): Appetite suppression becomes more noticeable. Some patients report feeling full sooner during meals. Mild nausea may appear, particularly in the first few days after the dose increase. Weight loss accelerates. At 24 weeks on the combined 4 mg groups, participants had lost an average of 12.9% of body weight [1].

Weeks 9-12 (8 mg): This is where most patients feel the full effects. Appetite is significantly reduced. Gastrointestinal side effects (nausea, diarrhea, constipation) are most likely to appear or worsen during this transition. The 8 mg dose produced 22.8% weight loss at 48 weeks [1], which is comparable to the maximum tirzepatide dose.

Week 13+ (12 mg): The highest tested dose and the most effective for weight loss. GI side effects may temporarily increase again with this step. Dysesthesia (tingling sensations) was reported in about 21% of patients at this dose [2]. Most side effects stabilize within 2-4 weeks of reaching a steady dose.

For detailed side effect information at each dose level, see our retatrutide side effects page.

How retatrutide dosing compares to other medications

Understanding where retatrutide fits relative to drugs you might already know about helps put the doses in context:

Medication	Receptor targets	Dose range	Max dose	Dosing frequency
Retatrutide	GIP + GLP-1 + glucagon	2-12 mg	12 mg	Once weekly
Tirzepatide	GIP + GLP-1	2.5-15 mg	15 mg	Once weekly
Semaglutide	GLP-1	0.25-2.4 mg	2.4 mg	Once weekly

Retatrutide’s milligram doses are higher than semaglutide but comparable to tirzepatide. The key difference is not the dose number but the additional glucagon receptor activity. For a full breakdown, see our retatrutide vs tirzepatide comparison and semaglutide vs tirzepatide pages.

Frequently asked questions

What is the recommended starting dose of retatrutide?▼

Clinical trials started most patients at 2 mg weekly. Some protocols tested a 1 mg starting dose. There is no FDA-approved starting dose because retatrutide is still investigational. Your provider will determine the appropriate starting point based on your health status and tolerance.

How often do you increase the retatrutide dose?▼

Every 4 weeks in the standard protocol. The schedule is 2 mg for 4 weeks, then 4 mg for 4 weeks, then 8 mg for 4 weeks, then 12 mg ongoing. Phase 3 trials used a slower escalation over 20 to 24 weeks.

What is the maximum dose of retatrutide?▼

The highest dose tested in clinical trials is 12 mg weekly. Phase 3 trials used 9 mg and 12 mg as the two target maintenance doses. Whether higher doses will be studied in the future is unknown.

Can you stay on a lower dose of retatrutide?▼

Yes. The Phase 2 trial showed meaningful weight loss at every dose level tested, including 4 mg (-17.1%) and 8 mg (-22.8%) at 48 weeks [1]. Not every patient needs or tolerates the 12 mg dose. Eli Lilly is also studying a 4 mg maintenance dose for long-term weight maintenance.

How long does it take to reach the full dose?▼

Using the standard 4-week titration steps, you reach 12 mg at week 13. The Phase 3 slow titration takes 20 to 24 weeks to reach the target dose. The slower approach reduces gastrointestinal side effects during escalation.

What happens if you miss a dose of retatrutide?▼

Based on protocols for similar once-weekly injectables, take the missed dose as soon as you remember. If it has been more than 4 days since the missed dose, skip it and resume on your regular day. Do not take two doses in the same week.

Is retatrutide available now at these doses?▼

Not through FDA-approved channels. Some compounding pharmacies may prepare retatrutide at various concentrations, but these are not FDA-approved products. For how to access retatrutide through available pathways, see our access guide.

References

1. Jastreboff AM, Kaplan LM, Frías JP, et al. Triple-hormone-receptor agonist retatrutide for obesity — a phase 2 trial. N Engl J Med. 2023;389(6):514-526. doi:10.1056/NEJMoa2301972
2. Eli Lilly. Lilly’s triple agonist, retatrutide, delivered weight loss of up to an average of 71.2 lbs along with substantial relief from osteoarthritis pain in first successful Phase 3 trial. Press release. December 11, 2025.
3. Coskun T, Urva S, Roell WC, et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept. Cell Metab. 2022;34(9):1234-1247.