Retatrutide Pen Dosage Guide.

What is retatrutide?

Retatrutide is an investigational triple agonist that simultaneously activates the GLP-1, GIP, and glucagon receptors. That third axis — glucagon — increases energy expenditure on top of the appetite and insulinotropic effects familiar from semaglutide and tirzepatide. Phase 2 trials have reported the largest weight-loss signal among incretin compounds to date.

• Target

  GLP-1

  Satiety, insulin response

• Target

  GIP

  Glucose-dependent insulin release

• Target

  Glucagon

  Energy expenditure, lipolysis

Pen unit math

The standard retatrutide pen on this catalog is reconstituted to 10 mg/mL. The dial reads in units, where 100 units = 1 mL. To convert milligrams to units, divide dose by concentration and multiply by 100.

units = (dose_mg / concentration_mg_per_mL) × 100

# Example: 4 mg retatrutide on a 10 mg/mL pen
units = (4 / 10) × 100 = 40 units

Retatrutide titration schedule

Reference values based on a 10 mg/mL pen. Most published Phase 2 protocols escalate by 2 mg every 2–4 weeks based on tolerability, up to 8–12 mg weekly.

Hold or step back one dose level if gastrointestinal side effects become limiting. Hold-then-resume is preferred over discontinuing.

Storage & handling

• Store pens at 2–8°C; protect from light and freezing.
• Allow the pen to reach room temperature before administration.
• Prime the pen per manufacturer instructions before first use.
• Rotate subcutaneous sites; use a new needle every dose.
• Discard pens past their in-use period after first puncture.

Reported side effects

In published trials the most common adverse events were dose-dependent gastrointestinal: nausea, diarrhea, constipation, and vomiting — typically peaking during titration and tapering during maintenance. Slower titration (every 4 weeks rather than every 2) reduced incidence in Phase 2 data.

Frequently asked