Retatrutide Dosing Guide: Weekly Titration Schedule (UK)

Retatrutide is administered subcutaneously once weekly. In clinical study, dosing begins low and titrates upward every four weeks to allow gastrointestinal tolerance to develop. The Body Pharm multi-dose pen mirrors this format — a dialled dose, a single weekly injection, and a cartridge designed to last across several titration steps.

• Once-weekly subcutaneous administration
• Titrate every four weeks to manage tolerance
• Rotate injection sites (abdomen, thigh, upper arm)
• Maintain consistent day-of-week dosing

The schedule below reflects the high-dose arm titration used in the LY3437943 Phase II trial. Research applications may use this as a starting reference; actual study protocols vary.

Capacity figures are approximate and depend on the titration schedule followed.

• Store unopened pens refrigerated at 2–8°C.
• Refrigerated at 2–8°C, the pen stays stable for up to 12 months, including after first use.
• Do not freeze. Discard any pen that has been frozen.
• Keep the pen cap on between uses to protect the cartridge from light.
• Use a new sterile pen needle for each administration.

Across the published Retatrutide trials, the most commonly reported adverse events were gastrointestinal in nature and largely dose-dependent — nausea, diarrhoea, vomiting and constipation. Incidence diminishes with slower titration.

This page is a research reference only and does not replace consultation with a qualified clinician.

Retatrutide is an investigational triple GLP-1/GIP/glucagon agonist. It is not approved by the MHRA (or any medicines regulator) and is supplied strictly for in-vitro research — not for human use. The schedule on this page is a representative research reference, not a treatment protocol, and nothing here is medical advice.

• Dose-dependent gastrointestinal effects (nausea, vomiting, diarrhoea, constipation) are the most commonly reported adverse events across the class and tend to track titration speed.
• Retatrutide's glucagon-receptor activity was associated with a transient rise in heart rate in the published Phase 2 trial — a signal not seen with pure GLP-1 agonists.
• Long-term safety has not been established; the molecule remains in clinical development and figures here come only from the cited trials.
• This page does not cover individual risk factors (e.g. personal or family history of medullary thyroid carcinoma, MEN 2, pancreatitis, gallbladder or severe GI disease, pregnancy or breastfeeding) that a qualified clinician would assess before any GLP-1-class agent.

This section is a limitation of the page itself: it is an educational research reference, not a substitute for a consultation with a qualified clinician who can weigh an individual's circumstances.

Common questions from researchers comparing the Retatrutide titration schedule to Semaglutide (Ozempic / Wegovy) and Tirzepatide (Mounjaro).

How does the Retatrutide dosing schedule compare to Semaglutide?

Both follow a four-weekly titration ramp, but at different scales: Retatrutide ramps from 2 mg up to 10–12 mg weekly, while Semaglutide (Wegovy) climbs from 0.25 mg to 2.4 mg. See the full Retatrutide vs Semaglutide (Ozempic / Wegovy) comparison for side-by-side dosing tables.

How does the Retatrutide dosing schedule compare to Tirzepatide (Mounjaro)?

Tirzepatide titrates 2.5 → 15 mg weekly over the same 16-week ramp window that Retatrutide uses for its 2 → 12 mg climb. The cadence is near-identical; the mechanism is not. Read the Retatrutide vs Tirzepatide (Mounjaro) comparison for the full breakdown.

Can I switch from Semaglutide or Tirzepatide to Retatrutide on the same schedule?

In a research context, prior GLP-1 exposure is often used to justify starting one titration step higher, since GI tolerance is already established. Retatrutide remains investigational and is supplied strictly for in-vitro research — switching is not a human-use recommendation.

Is the side-effect profile during titration different from Semaglutide and Tirzepatide?

The dose-dependent GI signature (nausea, altered bowel habit, reduced appetite) is shared across all three. Retatrutide's glucagon-receptor activity adds a transient heart-rate rise observed in Phase 2 trials that is not seen with pure GLP-1 agonists like Semaglutide.

Why does Retatrutide's top dose look lower than Tirzepatide's 15 mg?

The numbers aren't directly comparable — they're different molecules at different molar potencies acting on different receptor combinations. Retatrutide's 12 mg studied dose produced ≈24% mean weight loss in Phase 2, exceeding Tirzepatide's ≈21% at 15 mg in SURMOUNT-1.