How to Reconstitute Retatrutide
Reconstituting Retatrutidemeans adding bacteriostatic water to the freeze-dried (lyophilized) powder so you can inject a measured dose. If you've just received a vial with a small disc of powder at the bottom, this is where you start.
- Clean the vial stopper with an alcohol swab. Let it dry completely.
- Draw bacteriostatic water into a syringe. We recommend 2 mL for most peptides. Most vials hold 3 mL or less.
- Inject the water slowly into the vial, aiming at the glass wall — not directly onto the powder. This prevents damaging the peptide.
- Gently swirl the vial until the powder is fully dissolved. Do not shake.
- Store in the refrigerator. Most reconstituted peptides last 4–6 weeks refrigerated.
After reconstitution, your vial won't be completely full — that's normal. A typical vial holds about 3 mL, and you're adding 1–3 mL of water. The dose is based on concentration, not how full the vial looks.
How to Draw a Dose
Drawing liquid from a sealed vial requires injecting air first. This equalizes the pressure inside the vial so the liquid flows smoothly into the syringe.
- Clean the vial stopper with a fresh alcohol swab.
- Pull back the plunger to draw air into the syringe — the same volume you plan to withdraw (e.g., if you need 20 units of liquid, draw 20 units of air).
- Insert the needle through the vial stopper and push the plunger to inject the air into the vial.
- Invert the vial so the stopper faces down, with the needle tip submerged in the liquid.
- Pull back the plunger slowly to your target unit mark.
- Check for air bubbles. If you see any, gently flick the barrel to move them toward the needle, then push the plunger slightly to force them back into the vial. Readjust to your target volume.
- Remove the needle from the vial. You're ready to inject.
Retatrutide Dosage Chart
Retatrutide is a triple-agonist peptide that targets GLP-1, GIP, and glucagon receptors simultaneously. It's currently in Phase 3 clinical trials. The dosing below is based on the published Phase 2 trial data (NEJM, 2023):
| Weeks | Weekly Dose | Phase |
|---|---|---|
| 1–4 | 1–2 mg | Initiation |
| 5–8 | 4 mg | Titration |
| 9–12 | 6 mg | Titration |
| 13–16 | 8 mg | Titration |
| 17–20 | 10 mg | Titration |
| 21+ | 12 mg | Maintenance |
In the Phase 2 trial, the 12 mg group saw up to 24.2% body weight loss over 48 weeks. Retatrutide is not yet FDA-approved — these doses are from clinical research data only.
Retatrutide Starting Dose
The recommended starting dose for retatrutide is 1–2 mg per week, based on Phase 2 trial protocols. Starting low is important because retatrutide activates three receptor pathways simultaneously, which can cause significant GI side effects if the dose ramps too quickly.
Stay at each dose level for at least 4 weeks before increasing. If side effects are significant, remain at the current dose for an additional 4 weeks. Most of the weight loss benefit comes from sustained use, not from reaching the highest dose quickly.
Understanding Peptide Dosing
The key concept is concentration. When you add 2 mL of water to a 10 mg vial, you get a concentration of 5 mg/mL. To dose 2.5 mg, you need 0.5 mL — which is 50 units on a standard insulin syringe.
Insulin syringes are marked in "units," where 100 units = 1 mL. So the math is simple: multiply the volume in mL by 100 to get your unit mark. The calculator above does this for you automatically.
Frequently Asked Questions
How is retatrutide different from semaglutide and tirzepatide?
Retatrutide is a triple agonist (GLP-1 + GIP + glucagon), while tirzepatide is a dual agonist (GLP-1 + GIP) and semaglutide targets GLP-1 only. The glucagon component may provide additional metabolic benefits including increased energy expenditure.
Is retatrutide FDA-approved?
No. Retatrutide is currently in Phase 3 clinical trials by Eli Lilly. It is available through research peptide suppliers but has not been approved for clinical use.
How long does reconstituted retatrutide last?
When mixed with bacteriostatic water and refrigerated, reconstituted retatrutide typically lasts 4–6 weeks. Keep the vial upright and avoid temperature fluctuations.