How to Use

How to Dose

Retatrutide is given as a subcutaneous injection taken once weekly, started at a low dose and stepped up every four weeks until the maintenance level is reached.

Sex

Height

Original Weight

Target Weight

Dose

Hover/hold on graph to see dosing.

Trial source: TRIUMPH-1 (Lilly, May 2026)

*For research and education purposes only

Weeks	Phase	Dose
1 – 4	Escalation	2 mg
5 – 8	Escalation	4 mg
9 – 12	Escalation	8 mg
13 – 38	Plateau	9 mg
39 – 46	Maintenance	4 mg

Tolerability note

Trial protocols use a single once weekly injection. Patients who still have nausea or GI discomfort at maintenance sometimes work with their physician to split the weekly dose into two smaller injections a few days apart, keeping the same total weekly exposure but lowering each peak.

How to Reconstitute

Peptides arrive as freeze-dried powder and must be reconstituted with bacteriostatic water into a clear liquid of known concentration before doses can be measured accurately.

Notes

Let the peptide vial and BAC water sit out 15–20 minutes before reconstituting, since cold vials can cause condensation and incomplete dissolving.

Label the vial with compound, concentration, and reconstitution date, then store reconstituted peptide at 2–8°C and unopened lyophilized vials at −20°C or colder away from light.

Reconstitution calculator

An insulin syringe is marked in “units” instead of mL: on the standard U-100 scale, 100 units equal 1 mL, so each unit is 0.01 mL. This calculator turns a vial of peptide plus a measured volume of bacteriostatic water into a working concentration, then converts a target dose into the matching draw on your syringe.

Peptide In Vial

BAC Water

Target Dose

Concentration

10mg/mL

Volume Per Dose

0.2mL

Syringe Units

Effects

Positive

Effect	Notes
Weight loss	~28.3% at 12 mg over 80 weeks; up to 30.3% in BMI ≥35 by 104 weeks (TRIUMPH 1, 2026)
Reduced appetite	primary driver of weight loss across all dose arms (TRIUMPH 1, 2026)
Improved blood sugar	2.0% HbA1c drop with 16.8% weight loss in type 2 diabetes (TRANSCEND-T2D-1, 2026)
Knee osteoarthritis pain relief	WOMAC pain fell ~76% in obesity + knee OA (TRIUMPH 4, 2025)
Improved lipids	lower triglycerides and LDL on treatment (Phase 2, 2023)
Lower blood pressure	modest drop in systolic blood pressure (Phase 2, 2023)
Quieter food noise	users describe far less intrusive background hunger (Community Notes)
Improved focus	attention freed from food preoccupation (Community Notes)
Reduced cravings	lower alcohol and substance cravings reported anecdotally (Community Notes)

Negative

Effect	Notes
Nausea	most common, 42.4% at 12 mg vs 14.8% placebo (TRIUMPH 1, 2026)
Vomiting	25.3% at 12 mg vs 4.8% placebo (TRIUMPH 1, 2026)
Diarrhea	32.0% at 12 mg vs 13.5% placebo, usually transient (TRIUMPH 1, 2026)
Constipation	26.1% at 12 mg vs 10.9% placebo (TRIUMPH 1, 2026)
Dysesthesia (skin tingling)	distinctive to reta, 7–21% at higher doses (Phase 2, 2023)
Heart rate increase	modest, dose-dependent, peaks ~24 weeks then declines (Phase 2, 2023)
Injection site reactions	mild redness or irritation (TRIUMPH 1, 2026)
Fatigue	occasional tiredness during early weeks (Community Notes)
Anhedonia	muted reward or flat affect reported by some users (Community Notes)

VIEW PRODUCTS

Disclaimer: The dosing, reconstitution, and effect notes above summarize publicly available clinical and community-reported data. Modern Bio sells materials for in vitro and laboratory research only, and nothing on this page is medical advice.