Which format?
| Pre-filled pen | Vial | |
|---|---|---|
| Strength per pen | 15, 20, 30 or 70 mg of retatrutide in total per pen | — |
| How supplied | Pre-filled pen containing retatrutide in solution; pen needles are sold separately or in the pen kit (20 needles and 20 alcohol swabs) | — |
| Needs mixing? | No. The pen is filled with solution, unlike the vials, which hold lyophilised powder for reconstitution | Yes, with BAC water |
| Storage | Refrigerated at 2–8 °C, protected from light, not frozen | −20 °C dry; 2–8 °C mixed |
Storage and handling
Keep the pen in the refrigerator at 2–8 °C in its box, away from light, and do not freeze it. A peptide in solution is less stable than dry powder, so a pen has a shorter storage life than an unopened vial; if long-term storage matters to the research plan, the lyophilised vials kept at −20 °C are the better fit.
Studies
| Study | Model | Dose used | Duration | Finding |
|---|---|---|---|---|
| Jastreboff AM et al.2023 · N Engl J Med · PMID 37366315 | Human, phase 2 randomised controlled trial in adults with obesity (n=338) | 1, 4, 8 or 12 mg once weekly, subcutaneous | 48 weeks | Given by subcutaneous injection once weekly; mean body weight change at 48 weeks ranged from −8.7% (1 mg) to −24.2% (12 mg) vs −2.1% with placebo. The abstract does not state the injection device used. |
| Bajaj HS et al.2026 · Lancet · PMID 42250575 | Human, phase 3 randomised controlled trial in type 2 diabetes (n=537) | 4, 9 or 12 mg once weekly, subcutaneous | 40 weeks | Once-weekly subcutaneous injection lowered HbA1c by 1.69% to 1.94% vs 0.81% with placebo. The abstract does not state the injection device used. |
| Sanyal AJ et al.2024 · Nat Med · PMID 38858523 | Human, phase 2a randomised controlled substudy in MASLD (n=98) | 1, 4, 8 or 12 mg once weekly, subcutaneous | 48 weeks | Relative liver fat change at 24 weeks ranged from −42.9% to −82.4% vs +0.3% with placebo. The abstract does not state the injection device used. |
| Urva S et al.2022 · Lancet · PMID 36354040 | Human, phase 1b randomised multiple-ascending dose trial in type 2 diabetes (n=72) | 0.5 to 12 mg once weekly, subcutaneous | 12 weeks | Treatment-emergent adverse events were reported by 63% on LY3437943 vs 54% on placebo, mostly gastrointestinal. The abstract does not state the injection device used. |
Pre-filled pen FAQ
What is a retatrutide pen?
A retatrutide pen is a pre-filled pen that holds 15, 20, 30 or 70 mg of retatrutide already in solution, so there is no powder to reconstitute. Tasman supplies it for laboratory research only, with HPLC testing on each lot. The published trials gave retatrutide by subcutaneous injection, but their abstracts do not say what device was used.
Retatrutide pen or vial: which should I choose for research?
Choose the vial when storage life and flexible concentration matter, and the pen when a ready-made solution is more practical. The vials hold dry powder that keeps longest at −20 °C and is reconstituted to whatever concentration the work needs. The pen is already in solution at a fixed concentration and has to stay refrigerated.
What is the difference between the 15, 20, 30 and 70 mg pens?
The 30 mg pen contains 10 mg more retatrutide than the 20 mg pen; the compound and testing are the same. The size table on this page shows the per-mg figure for each pen.
How do you store a retatrutide pen?
Keep the pen refrigerated at 2–8 °C, in its box and away from light, and never freeze it. Because the peptide is already in solution, it will not keep as long as an unopened lyophilised vial stored at −20 °C.
Does the pen come with needles?
The pen on its own does not include needles. The retatrutide pen kit contains the pen, 20 pen needles and 20 alcohol swabs, and is available in 20 mg and 30 mg sizes.
The full Retatrutide rundown
Research, vial sizes, storage and FAQs are on the main Retatrutide page.
View Retatrutide →