For in-vitro laboratory research only. Not for human or veterinary use.Research Use Only
Research — Dosage Reference
Retatrutide Dosage FAQ: 15 Common Questions Answered
By Dr. Nadia Haroun, PharmD · Research Director · April 2026
Dr. Nadia Haroun, PharmD··TRIUMPH-4 + TRANSCEND-T2D-1 Phase 3 data
Fact-checked·
Reviewed by Dr. Nadia Haroun, PharmD
TL;DR — Verdict
This is a comprehensive dosage FAQ covering the 15 most frequently asked questions about retatrutide dosing protocols. Answers are based on Phase 3 trial data from TRIUMPH-4 (December 2025) and TRANSCEND-T2D-1 (March 2026). Topics include the recommended starting dose (2 mg weekly), the standard 4-week titration schedule (2 mg → 4 mg → 8 mg → 12 mg), pen click calculations for the 30 mg multi-dose pen, missed dose protocols, storage requirements, and how retatrutide dosing compares to semaglutide. For Research Use Only.
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Janoshik-verified, HPLC ≥99.2% purity. Retatrutide Pen 30 mg from AED 1,500/pen. Ships from Dubai.
Retatrutide (LY3437943) is a first-in-class triple hormone receptor agonist activating the GLP-1, GIP, and glucagon receptors simultaneously. It is administered as a once-weekly subcutaneous injection using a pre-filled multi-dose pen. As retatrutide advances through the TRIUMPH Phase 3 clinical program, dosing questions are among the most common inquiries from the research community. This FAQ compiles the 15 most frequently asked dosage questions, with answers grounded in published Phase 2 data (Jastreboff et al., NEJM 2023), TRIUMPH-4 topline results (December 2025), and TRANSCEND-T2D-1 topline results (March 2026). Retatrutide is an investigational research compound not yet approved by any regulatory authority. For Research Use Only.
Getting Started
Questions 1–5 — Basics of Retatrutide Dosing
Q1: What is the recommended starting dose of retatrutide?
In Phase 3 clinical trials (TRIUMPH-4 and TRANSCEND-T2D-1), retatrutide was initiated at 2 mg once weekly. This low starting dose was specifically selected to minimise gastrointestinal side effects during the initial adaptation period before titration to higher doses. Phase 2 data demonstrated that cohorts starting at 2 mg experienced 30–50% lower nausea rates compared to those starting at 4 mg.[1]
Q2: How is retatrutide administered?
Retatrutide is administered as a once-weekly subcutaneous injection using a pre-filled multi-dose pen. The injection is typically given in the abdomen, thigh, or upper arm. Injection sites should be rotated each week to reduce the risk of local reactions such as mild erythema or induration, which were reported at low rates in clinical trials.
Q3: What pen sizes are available for retatrutide?
Remy Peptides supplies a 30 mg multi-dose pen with 300 clicks at 0.1 mg per click, verified at 99.262% HPLC purity by Janoshik Analytical (Batch RETP002). This pen format allows precise dose selection across the full titration range from 2 mg to 12 mg per week. View pen specifications and pricing →
Q4: How many clicks equal 1 mg on the 30 mg pen?
Each click on the 30 mg retatrutide pen delivers 0.1 mg. Therefore, 10 clicks = 1 mg, 20 clicks = 2 mg (starting dose), 40 clicks = 4 mg, 80 clicks = 8 mg, and 120 clicks = 12 mg (maximum dose). Use the retatrutide dosage calculator for precise click counts at any dose level, including fractional doses used during custom titration protocols.
Q5: Is retatrutide taken daily or weekly?
Retatrutide is taken once weekly. The compound’s pharmacokinetic profile supports a 7-day dosing interval, with steady-state plasma concentrations maintained throughout the week. In clinical trials, participants administered their dose on the same day each week to maintain consistent drug levels.
Titration & Dose Adjustment
Questions 6–10 — Escalation, Side Effects, and Missed Doses
Q6: What does the retatrutide titration schedule look like?
The Phase 3 titration protocol starts at 2 mg weekly for 4 weeks, then escalates by one dose level every 4 weeks: 2 mg → 4 mg → 8 mg → 12 mg. Each 4-week period allows gastrointestinal adaptation before the next increase. This slow-escalation design was informed by Phase 2 data showing that rapid titration nearly doubled nausea rates at equivalent doses. For complete titration tables with week-by-week click counts, see our retatrutide dosage guide.
Q7: How long does it take to reach the maximum dose?
Using the standard 4-week titration schedule (2 mg → 4 mg → 8 mg → 12 mg), it takes approximately 16 weeks (4 months) to reach the maximum 12 mg maintenance dose. This timeline was validated in TRIUMPH-4, where the optimised slow-titration protocol produced lower GI adverse event rates than the rapid-escalation cohorts evaluated in Phase 2.[1] For detailed titration timelines, see the dosage guide.
Q8: What if I experience side effects during dose escalation?
In clinical trial protocols, participants who experienced significant gastrointestinal side effects could remain at their current dose level for an additional 4 weeks before escalating. This extended adaptation period was the primary tolerability strategy used in the TRIUMPH program. Some participants in Phase 2 also had their dose reduced by one level temporarily before re-escalating. For detailed adverse event rates by dose, see our retatrutide side effects article.
Q9: Can I skip a titration step?
Skipping titration steps is not recommended based on clinical trial data. Phase 2 rapid-escalation cohorts that started at higher doses experienced substantially higher nausea rates—the 8 mg rapid-start group had approximately 60% nausea compared to ~33% with slow titration to the same dose.[1] The titration protocol exists specifically to reduce adverse event severity and minimise early discontinuation.
Q10: What happens if I miss a weekly dose?
In clinical trial protocols, if a dose was missed, participants were generally instructed to administer it as soon as possible within 3–4 days of the scheduled date. If more than 4 days had passed, the missed dose was skipped and the next scheduled dose was taken on the regular dosing day. Double doses were not administered to compensate for a missed dose.
Questions 11–15 — Pen Duration, Storage, and Comparisons
Weekly Dose
Clicks per Dose
Doses per Pen
Pen Duration
2 mg
20
15
15 weeks
4 mg
40
7
7 weeks
8 mg
80
3
3 weeks
12 mg
120
2
2.5 weeks
Note: Pen duration is calculated for the 30 mg / 300-click pen format. At the 12 mg maintenance dose, each pen provides 2 full doses plus a partial third dose (300 ÷ 120 = 2.5). Use the dosage calculator for exact pen counts across your full protocol.
Q11: How long does one 30 mg pen last?
Pen duration depends entirely on weekly dose. At the 2 mg starting dose, one 30 mg pen lasts 15 weeks (300 clicks ÷ 20 clicks/dose = 15 doses). At the 12 mg maximum dose, one pen lasts approximately 2.5 weeks (300 ÷ 120 = 2.5 doses). During titration, pen consumption increases progressively as the dose escalates. The dosage calculator provides exact pen duration at any dose level.
Q12: How many pens do I need for a full protocol?
A full 48-week protocol (matching the Phase 2 trial duration) at the maximum 12 mg dose requires approximately 16–19 pens, depending on titration speed. The 16-week titration phase uses less compound per week than the maintenance phase. The 32-week maintenance period at 12 mg consumes approximately 12–13 pens alone. For precise pen counts at any protocol length and dose, use the dosage calculator.
Q13: How do I store the retatrutide pen?
Retatrutide pens should be stored refrigerated at 2–8°C (36–46°F) and protected from direct light. The pen should never be frozen. Once in use, the pen may be kept at room temperature (below 30°C / 86°F) for up to 28 days. Any remaining compound should be discarded after 28 days at room temperature.
Q14: What is the difference between retatrutide and semaglutide dosing?
Both are administered once weekly via subcutaneous injection, but they differ in dose range and titration. Semaglutide (Wegovy) titrates from 0.25 mg to 2.4 mg over 16–20 weeks, while retatrutide titrates from 2 mg to 12 mg over 16 weeks. Retatrutide’s higher absolute doses reflect its different receptor-binding profile as a triple agonist (GLP-1 + GIP + glucagon) versus semaglutide’s single GLP-1 pathway. For a full mechanism and efficacy comparison, see our retatrutide dosage comparison analysis.
Q15: Can I use a dosage calculator for retatrutide?
Yes. The Remy Peptides dosage calculator converts any target dose into exact pen click counts, calculates pen duration at each dose level, and estimates total pens needed for a complete research protocol. It is calibrated for the 30 mg / 300-click pen format and supports custom titration schedules.
Our Research Standards
This article cites peer-reviewed studies, FDA filings, and ClinicalTrials.gov data. All claims are cross-referenced against primary sources. We update articles when new trial data or regulatory decisions are published. Read our editorial policy →
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About the Author
Dr. Nadia Haroun, PharmD
Research Director, Remy Peptides
Dr. Haroun leads editorial review across all research articles covering GLP-1 receptor agonists, triple agonists, and the obesity drug pipeline. Her work spans peptide analytical chemistry, HPLC purity validation, and clinical trial data interpretation.
Jastreboff AM, 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
Eli Lilly and Company. Lilly’s retatrutide (LY3437943) met primary endpoint in TRIUMPH-4 Phase 3 obesity trial. Press release, December 11, 2025.
Eli Lilly and Company. Lilly announces positive topline results from TRANSCEND-T2D-1 Phase 3 trial of retatrutide in type 2 diabetes. Press release, March 19, 2026.
Eli Lilly. TRIUMPH Clinical Trial Program for Retatrutide — Phase 3 Design. ClinicalTrials.gov.
Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384(11):989-1002.
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99.262% HPLC purity, Janoshik Analytical. 300 clicks per pen, ships from Dubai.