Retatrutide 20mg Complete Guide: Dosing, Reconstitution, and Research

Dosing Guide — 2026-11-09

Retatrutide — sold here as Reta 20mg — is a triple-receptor agonist studied for metabolic and weight-loss research, targeting the GLP-1, GIP, and glucagon receptor systems simultaneously. This complete guide covers what retatrutide is, how to reconstitute the 20mg vial, the weekly titration protocol in exact syringe units, and vial longevity. The numbers match our Reta 20mg protocol page and Reta 20mg dosage guide.

> Naming note: "Retatrutide" and "Reta" are the same compound. Our product is listed as Reta 20mg for brevity — if you searched for retatrutide 20mg, this is it. More on the naming in retatrutide vs reta.

Researcher special: code SAVE25 or PLATINUM25 unlocks 25% off Reta 10mg and Reta 20mg plus bacteriostatic water. Every vial ships with a batch-matched COA at 99%+ HPLC purity.

What retatrutide is

Retatrutide is a triple agonist — it interacts with three metabolic receptor systems at once:

GLP-1 — incretin signaling and appetite regulation
GIP — glucose-dependent insulinotropic signaling
Glucagon — energy expenditure and fat metabolism

This three-pathway action is what distinguishes it from single-agonist (GLP-1 only) and dual-agonist compounds in metabolic research. For the compound profile, see what is Reta.

Reconstitution math: Reta 20mg

Standard reconstitution: add exactly 2 mL bacteriostatic water to the 20 mg vial.

Metric	Value
Peptide	20 mg
Bac water	2 mL
Concentration	10 mg/mL
Per 10 units (U-100 syringe)	1 mg

So 10 units = 1 mg, 20 units = 2 mg, 40 units = 4 mg. (The 20mg vial uses 2 mL — double the water of the 10mg vial — so the per-unit math is identical: 10 units = 1 mg either way. The 20mg vial simply lasts twice as long.)

Weekly titration protocol

Retatrutide is dosed once weekly, titrated up slowly to manage tolerability:

Week	Dose	Units
Week 1	2 mg	20 units
Week 2	3 mg	30 units
Week 3 onward	4 mg	40 units

4 mg (40 units) weekly is the standard target for weight-loss research — most results come at this dose without going higher.
If appetite control is already comfortable at 2 mg (20 units), hold there as maintenance.
If nausea appears, drop to 1 mg (10 units) or 0.5 mg (5 units) until symptoms settle, then re-titrate.
If results stall after ~6–8 weeks at 4 mg, step up to 6 mg (60 units), then 8 mg (80 units) — one step at a time, only after at least 2 months at the lower dose.
Maintenance after reaching the goal: 1–2 mg (10–20 units) weekly.

How long does a Reta 20mg vial last?

Weekly dose	Units/week	Weeks per 20mg vial
4 mg	40 units	~5 weeks
2 mg	20 units	~10 weeks
1 mg (maintenance)	10 units	~20 weeks

At the 4 mg target, a single Reta 20mg vial covers ~5 weeks — twice as long as the Reta 10mg vial at the same dose, which makes the 20mg the more economical choice for a full run. See Reta 10mg vs 20mg.

Administration and cycling

Route: Subcutaneous, once per week. Rotate injection sites week to week.
Protein + training: Eat adequate protein (≈1 g per lb lean mass) and keep up resistance training to preserve muscle during rapid loss.
Side effects: Nausea and fatigue are most common in weeks 1–2 and after titration steps; constipation is common (a fiber supplement helps). Hold the current dose an extra week rather than pushing through intense side effects.
Refrigerate after reconstitution and use within 4 weeks.

For the full step-by-step dosage walkthrough, see the Reta 20mg dosage guide and Reta 20mg complete guide.

Disclaimer: All information presented in this article is for educational and informational purposes only. Platinum Biolabs does not promote or endorse the use of peptides for human consumption. All products sold by Platinum Biolabs are intended strictly for laboratory and research use only. Consult a qualified healthcare professional before making any health-related decisions.