Retatrutide Dosing Schedule: Week-by-Week Protocol (1mg to 12mg)

Overview of Retatrutide

What is Retatrutide?

Retatrutide is an investigational, once-weekly injectable peptide that activates three receptors: GLP-1, GIP, and glucagon. Semaglutide targets only GLP-1; tirzepatide targets GLP-1 and GIP. The added glucagon receptor activation increases energy expenditure and fat oxidation, which likely explains the higher weight loss numbers in trials.

Mechanism of Action

Each receptor does something different: GLP-1 suppresses appetite and slows digestion, GIP improves insulin sensitivity and fat metabolism, and glucagon increases energy expenditure. The combination produced 24.2% weight loss at the 12mg dose in Phase 2 trials, the highest reported for any GLP-1 class medication so far.

Clinical Trials and Research

The Phase 2 trial (published in NEJM, 2023) enrolled 338 adults with obesity. At 48 weeks, the 12mg group lost an average of 24.2% body weight. Phase 3 TRIUMPH trials are ongoing, with early TRIUMPH-4 data showing 28.7% weight loss at 68 weeks. FDA approval is expected in 2027.

Standard Dosing Protocol

Initial Dosage Recommendations

Most protocols start at 1mg weekly (conservative community approach) or 2mg weekly (Phase 2 trial protocol). The low starting dose isn't for weight loss. It's to let your GI system adapt before increasing. Nausea and diarrhea are the main reasons people struggle with titration, so starting low pays off.

Maintenance Dose Guidelines

Your maintenance dose is wherever you get good results without intolerable side effects. For many people, that's 8mg weekly. The Phase 2 trial showed 22.8% weight loss at this dose. The 12mg maximum adds about 1.4 percentage points more weight loss but with higher GI side effect rates. Not everyone needs to push to 12mg.

Retatrutide Dosage Chart

For a printable reference, see our retatrutide dosage chart with the full Phase 2 titration table.

Track your weekly dose, side effects, and weight changes to see how you're responding at each level. Our free calculator plots retatrutide levels over time so you can see when you'll reach steady state and how drug concentrations change between injections.

Titration Schedules

Importance of Titration

Jumping straight to 8mg or 12mg would cause severe nausea and vomiting for most people. Titration gives your GI system time to adapt to each dose level before increasing. The Phase 2 trial used 4-week intervals between increases, and groups that followed dose escalation had better tolerability than those started at fixed higher doses.

Suggested Titration Schedule

Here's an example of how a typical retatrutide dosing schedule might progress. It usually begins with a low starting dose and gradually increases. This titration could look something like this:

1. Start with 1 mg weekly via subcutaneous injection.
2. Increase the dose every 4 weeks, by 2 mg increments, until the desired weight loss results are achieved.

For example, the schedule could progress to 2 mg, then to 4 mg, 6 mg, 8 mg, 10 mg, and potentially 12 mg per week. Remember, this is just an example, and your individual titration schedule may vary based on your healthcare provider's recommendations and your tolerance to retatrutide.

Monitoring and Adjustments

Track your weight, side effects, and how you feel at each dose level. If nausea or vomiting persists beyond the first week after an increase, stay at your current dose for another 4 weeks before trying again. Some people stay at 4mg or 8mg for 6-8 weeks before moving up. That's fine. The schedule is a guideline, not a hard rule.

Microdosing Protocols

Introduction to Microdosing

Microdosing means splitting your weekly dose into smaller, more frequent injections. For example, 4mg twice a week instead of 8mg once. The goal is smoother drug levels (lower peaks, higher troughs), which can reduce the nausea spike that hits 1-2 days after a full weekly injection.

Benefits of Microdosing Retatrutide

Splitting doses can reduce peak-related nausea by ~28-48% depending on frequency (see our dosing guide for the pharmacokinetic modeling). The trade-off: more injections per week and no clinical trial data validating this approach. It's based on pharmacokinetic theory and community experience, not controlled studies.

Microdosing Protocols for Retatrutide

Common split-dose approaches: twice weekly (e.g., 4mg Mon + 4mg Thu for an 8mg total) or three times weekly (e.g., 2.7mg Mon/Wed/Fri). Some people even do daily sub-milligram doses during the initial titration phase. See our full microdosing retatrutide guide for detailed protocols and peak reduction calculations.

Dosing Strategies for Weight Loss

Weight Loss Results with Retatrutide

Phase 2 trial results by dose: 1mg produced 8.7% weight loss, 4mg hit 17.3%, 8mg reached 22.8%, and the 12mg group lost 24.2% at 48 weeks. For context, semaglutide (Wegovy) tops out around 15% and tirzepatide (Zepbound) around 20.9%. Early Phase 3 TRIUMPH-4 data pushes even higher at 28.7% with 12mg at 68 weeks.

Comparative Analysis: Retatrutide vs. Tirzepatide

Tirzepatide targets two receptors (GLP-1 + GIP); retatrutide targets three (adding glucagon). The extra glucagon activation increases energy expenditure and fat oxidation, which likely accounts for the ~2% higher weight loss in trials. That said, these numbers come from different studies with different populations and durations. No head-to-head trial exists yet. See our full comparison for details.

Calculating Dosage Based on Body Weight

Clinical trials used fixed doses (not weight-based), so there's no official mg/kg recommendation. In practice, heavier individuals sometimes need higher maintenance doses to see the same appetite suppression effect. The titration approach handles this naturally. You increase until you find the dose that works for you, whether that's 4mg, 8mg, or 12mg.

Calculator Integration

Using Dosing Calculators

Our free dosing calculator models retatrutide pharmacokinetics based on your specific schedule. Enter your doses and timing to see projected drug concentration curves, when you'll hit steady state, and how peak-to-trough ratios change with different protocols.

Charting Retatrutide Levels

Plotting your drug levels over time shows the build-up pattern clearly: with a ~6-day half-life, retatrutide accumulates over 4-5 weeks before reaching steady state — a behaviour explained by first-order pharmacokinetics. This is why 4-week titration intervals make sense. You need to see the full effect of a dose before deciding to increase.

Create Charts to Visualize Retatrutide Levels

Try it on our calculator. Enter your protocol, and it generates a shareable URL with your projected drug level chart. Useful for discussing your schedule with a provider or comparing weekly vs. split-dose approaches side by side.

Frequently Asked Questions