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Reviewed by MyPeptideMatch Editorial TeamLast reviewed February 2026Updated February 2026

Retatrutide Dosing Protocol: 20 mg Vial — Week-by-Week Titration & Supplies

High-concentration retatrutide protocol for patients advancing to 8–12 mg maintenance using the 20 mg compounded vial.

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Quickstart highlights

The 12 mg dose of retatrutide produced 24.2% mean body weight reduction at 48 weeks (NCT04881760), superior to all other approved or investigational anti-obesity agents in comparable trial designs.

  • Concentration: 10 mg/mL (20 mg vial + 2 mL bacteriostatic water).
  • At 10 mg/mL: 1 mg = 10 units, 4 mg = 40 units, 8 mg = 80 units, 12 mg = 120 units.
  • Phase 2 trial: 12 mg dose achieved 24.2% mean weight reduction — highest ever reported for anti-obesity pharmacotherapy.
  • One 20 mg vial provides 2.5 doses at 8 mg or ~1.67 doses at 12 mg maintenance.
  • Double-check units — concentration here (10 mg/mL) is double the standard 5 mg/mL vials.

Dosing table

For educational reference only. Your prescribing provider may adjust doses based on your clinical profile and response.

WeekDose (µg)UnitsFrequencyNotes
1-4100010Once weekly1 mg — 10 units at 10 mg/mL; 20 starting doses per vial
5-8200020Once weekly2 mg — 20 units
9-12400040Once weekly4 mg — 40 units; 5 doses per vial
13-16800080Once weekly8 mg maintenance — 80 units; 2.5 doses per vial
17+12000120Once weekly12 mg maximum — 120 units; ~1.67 doses per vial

Reconstitution steps

  1. Draw 2 mL bacteriostatic water; inject slowly down the vial wall.
  2. Swirl gently until powder dissolves; do not shake.
  3. Final concentration: 10 mg/mL (20 mg / 2 mL). Note: double the concentration of 5 mg/mL vials — verify units.
  4. Label with date and 10 mg/mL; refrigerate at 2–8 °C.

Supplies needed

12-week plan

  • 1 vial
  • 12 syringes
  • 2 mL bac water
  • 12 alcohol swabs

20-week plan

  • 2 vials
  • 20 syringes
  • 4 mL bac water
  • 20 alcohol swabs
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Protocol overview & cycle notes

Support advanced retatrutide dosing up to the 12 mg maximum studied in Phase 2 trials, using the 20 mg high-concentration vial for efficient maintenance dosing at 8–12 mg weekly.

Cycle length: 20 weeks on.

Off-cycle: 8–12 weeks off between cycles.

Storage & handling

Lyophilized: store below 25 °C. Reconstituted at 10 mg/mL: refrigerate 2–8 °C; use within 28 days. Do not freeze. Note concentration is 10 mg/mL — half the units of a 5 mg/mL vial for the same dose.

Injection & tracking tips

  • CRITICAL: At 10 mg/mL, 1 unit = 100 µg. This is half the units needed compared to 5 mg/mL vials. Do not use your 5 mg/mL unit chart for this vial.
  • The 20 mg vial is most economical for patients at 8–12 mg maintenance — each vial provides 2–2.5 weekly doses.
  • Use a 1 mL U-100 syringe for doses ≤10 mg (100 units); use a 3 mL syringe for the 12 mg dose (120 units = 1.2 mL).

Tracking

Logging helps you and your provider spot patterns and adjust dose or timing.

  • Monitor body weight weekly; expect slowdown in rate of loss after reaching maintenance dose.
  • Track liver enzyme labs (ALT/AST) monthly — glucagon agonism improves hepatic steatosis.
  • Record energy, hunger, and satiety scores daily for the first 4 weeks at each new dose level.
Log your cycle in the calculator →

How this works & references

The 12 mg dose of retatrutide produced 24.2% mean body weight reduction at 48 weeks (NCT04881760), superior to all other approved or investigational anti-obesity agents in comparable trial designs. Glucagon receptor agonism produces meaningful hepatic fat reduction (MRI-PDFF data) independent of weight loss.

Sources

Frequently asked questions

Why use 10 mg/mL instead of 5 mg/mL for the 20 mg vial?
Reconstituting 20 mg into 2 mL yields 10 mg/mL, which keeps injection volumes manageable (0.8 mL for 8 mg, 1.2 mL for 12 mg). At 5 mg/mL, an 8 mg dose would require 1.6 mL — still feasible but less precise with a standard 1 mL syringe.
Is 12 mg the maximum retatrutide dose?
In the published Phase 2 trial, 12 mg was the highest dose arm. Phase 3 protocols are evaluating specific doses; clinical compounding protocols typically cap at 12 mg based on available safety data.
How does 10 mg/mL affect my unit calculation?
At 10 mg/mL, divide the dose (in mg) by 10, then multiply by 100 to get units. Example: 8 mg ÷ 10 × 100 = 80 units. At 5 mg/mL: 8 mg ÷ 5 × 100 = 160 units. Always verify concentration before drawing.
What are the most common side effects at 8–12 mg?
Nausea, vomiting, and diarrhea occur in 40–60% of patients during the first 4–8 weeks at each new dose level. These typically improve with continued use. The 12 mg arm in Phase 2 had higher GI rates than lower doses but similar tolerability after 12 weeks.
When is the best time to inject retatrutide?
Once weekly at a consistent day and time (±24 hours). Injecting in the morning may minimize overnight GI discomfort; however, individual preference should guide timing. Avoid injecting directly before a large meal.

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This content is for informational purposes only and does not constitute medical advice. Consult a licensed healthcare provider before starting any peptide therapy. Dosing and protocols may vary by formulation and prescriber.

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