Retatrutide (10 mg vial)
Once weekly subcutaneous protocol for metabolic and weight-management research.
Retatrutide is a triple agonist hitting the GLP-1, GIP and glucagon receptors at once, still in late-stage trials, where phase 2 subjects lost up to a quarter of their body weight. The protocol below is a once-weekly subcutaneous escalation run deliberately slower than the single-agonist drugs because the glucagon arm adds side effects of its own.
Quick answer: at the standard 10 mg + 1 mL reconstitution, a 8 mg dose of Retatrutide draws 80 units (0.8 mL) on a U-100 insulin syringe, once weekly subcutaneous.
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Protocol overview
Dosing & reconstitution
Frequency: Once weekly subcutaneous
Typical duration: 12-48 weeks
Reconstitution: 10 mg vial + 1 mL bacteriostatic water = 10 mg/mL. Units below are for a U-100 insulin syringe at this concentration.
| Phase | Dose | Units per injection |
|---|---|---|
| Weeks 1-4 | 2 mg | 20 units (0.2 mL) |
| Weeks 5-8 | 4 mg | 40 units (0.4 mL) |
| Weeks 9-12 | 6 mg | 60 units (0.6 mL) |
| Week 13+ | 8 mg | 80 units (0.8 mL) |
Units = (dose ÷ concentration) × 100 on a U-100 syringe. Change the vial size or water volume and the calculator redoes all of this for you.
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Retatrutide dosing schedule
The phase 2 trial did not run one titration ladder. Participants were randomly assigned to a maintenance amount of 1, 4, 8 or 12 mg — and, for the 4 mg and 8 mg groups, also to one of two different starting steps, so the trial could compare escalation schemes as well as amounts. Each row below is one of the six retatrutide groups, not a step somebody worked through on the way to the next row. The protocol raised the amount in four-week increments, with all escalation finished by week 12; whatever amount a group reached was then continued for the rest of the trial. This compound is still investigational — there is no approved label anywhere, so none of this reflects approved dosing.
| Phase | Amount | Frequency | Notes |
|---|---|---|---|
| 1 mg group | 1 mg | Once weekly | No escalation — 1 mg from the first injection. |
| 4 mg group, 2 mg start | 2 mg -> 4 mg | Once weekly | One four-week step. Randomised 1:1 against the group below to compare starting steps. |
| 4 mg group, 4 mg start | 4 mg | Once weekly | No escalation — 4 mg from the first injection. |
| 8 mg group, 2 mg start | 2 mg -> 4 mg -> 8 mg | Once weekly | Two four-week steps. Randomised 1:1 against the group below. |
| 8 mg group, 4 mg start | 4 mg -> 8 mg | Once weekly | One four-week step. |
| 12 mg group | 2 mg -> 4 mg -> 8 mg -> 12 mg | Once weekly | Three four-week steps, reaching 12 mg at week 12. The highest group, and the only escalation scheme tested for it. |
Study length: 48 weeks, with all escalation completed by week 12. 338 adults randomised across placebo and the six retatrutide groups. Registry: NCT04881760.
Reconstitution and measurement
This part is arithmetic and does not depend on the evidence level. Concentration is vial size divided by the bacteriostatic water you add. Draw volume is your target amount divided by that concentration. Units are draw volume times 100, because a U-100 syringe reads 100 units per millilitre. Common vials for Retatrutide: 10, 15, 20, 30, 50 mg.
- Wipe the stoppers of both vials with an alcohol swab and let them dry.
- Draw the bacteriostatic water with a sterile syringe and inject it slowly down the inside wall of the peptide vial — never straight onto the powder.
- Swirl gently until the solution is clear. Do not shake; foaming and agitation damage peptides.
- Label the vial with the date and concentration, and refrigerate at 2–8 °C protected from light.
Worked example at the calculator defaults: 10 mg + 2 mL of bacteriostatic water = 5 mg/mL, so on a U-100 insulin syringe 1 unit = 50 mcg of Retatrutide. Change either input and the calculator redoes this for you.
Storage and stability
Supplies math
Whatever amounts your research uses, the planning arithmetic is the same. The calculator runs all of this per compound.
Supplies by protocol length
Based on the maintenance dose above (8 mg, once weekly subcutaneous) and a 10 mg vial reconstituted with 1 mL.
| Duration | Injections | Vials | Syringes | Bac water | Swabs |
|---|---|---|---|---|---|
| 8 weeks | 8 | 8 x 10 mg | 9 | 1 x 10 mL | 16 |
| 12 weeks | 12 | 12 x 10 mg | 14 | 2 x 10 mL | 24 |
| 16 weeks | 16 | 16 x 10 mg | 18 | 2 x 10 mL | 32 |
Syringe count includes ~10% spares. Swabs = 2 per injection (stopper + site). Vial count assumes the full maintenance dose for the entire duration.
Important notes
Practical considerations for consistency and safety.
- Use a new sterile insulin syringe for each injection and dispose in a proper sharps container.
- Rotate injection sites (abdomen, thighs, upper arms) systematically to reduce local irritation and avoid lipohypertrophy.
- Inject slowly and steadily; wait a few seconds before withdrawing the needle to ensure complete delivery.
- Administer on the same day each week for consistency. If a dose is missed, administer as soon as possible within a few days.
- The 10 mg vial size is standard for this compound. Reconstitute with 1 mL bacteriostatic water for a convenient concentration.
How Retatrutide works
Adds glucagon-receptor agonism to the GIP/GLP-1 combination. Glucagon activity is thought to raise energy expenditure directly, which is the proposed reason for the larger phase 2 weight changes.
Benefits & side effects
Potential benefits
- Triple agonist (GIP/GLP-1/glucagon) for enhanced fat loss
- Phase 2 showed up to 24% body weight reduction
- May improve liver fat and metabolic markers
- Glucagon component may support energy expenditure
Possible side effects
- GI side effects more common than single agonists
- Nausea and diarrhoea during escalation
- Heart rate increase reported in some subjects
- Very slow escalation recommended
This list reflects published literature and community reports. Individual responses vary. Not medical advice.
Bloodwork worth tracking
The community-standard practice is a baseline panel before starting, a recheck 8 to 12 weeks in, and another after time off. For Retatrutide, the markers most worth watching:
HbA1clipid panelCMPamylase/lipasethyroid panel
Typical time off: Taper off over 4-8 wks
Lab panels are how a research protocol stays honest: numbers move before symptoms do. Interpretation belongs with a clinician. Not medical advice.
Lifestyle factors
None of the literature above was run on a background of poor sleep and no protein. These variables move outcomes more reliably than any compound on this site.
- Protein in the 1.6 to 2.2 g/kg range preserves lean mass through any body-composition phase.
- Resistance training 2 to 4 days per week plus 150+ minutes of weekly aerobic work reinforces whatever the protocol is doing.
- Sleep is the recovery window: 7 to 9 hours at consistent times.
- Hydration matters more than usual on compounds with GI or flushing effects: 2 to 3 liters daily.
- Track the variables that matter: weigh-ins, measurements, photos, and labs at sensible intervals.
Subcutaneous technique and practical notes
General best practice from clinical injection guidance — the same fundamentals nurses are taught, none of it specific to any compound.
References
Quick answers
How many syringe units is a 8 mg dose of Retatrutide?
At the standard reconstitution of 10 mg with 1 mL bacteriostatic water (10 mg/mL), a 8 mg dose draws 80 units (0.8 mL) on a U-100 insulin syringe.
How do you reconstitute Retatrutide?
Add 1 mL of bacteriostatic water to the 10 mg vial for 10 mg/mL. Inject the water slowly down the inside wall of the vial, swirl gently without shaking, and refrigerate at 2 to 8 °C after mixing.
How long does a 10 mg vial of Retatrutide last?
About 1 maintenance doses of 8 mg, roughly 1 week at once weekly subcutaneous.
Does Retatrutide have human trial data?
Yes. The dosing on this page is anchored to published human research (Jastreboff AM et al., "Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial", NEJM 2023).
How does Retatrutide work?
Adds glucagon-receptor agonism to the GIP/GLP-1 combination. Glucagon activity is thought to raise energy expenditure directly, which is the proposed reason for the larger phase 2 weight changes.
Sourcing Retatrutide
Whatever you are working with, the documentation matters more than the price. Ask for a batch certificate of analysis whose lot number matches the vial you actually receive — a COA for a different batch tells you nothing about yours.
Retatrutide at Summit Research Supply → Grade a COA first
Summit is the supplier we feature and an affiliate link. Our COA checklist applies the same way to any vendor.
