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Retatrutide · Dosing

How Retatrutide Is Actually Dosed

What does a real Retatrutide dose schedule look like?

S-Tier (pending) Weight Loss RCT (late-stage)

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The plain-English version

You start at 2mg once a week and step up every 4 weeks. Trial doses ran 1mg up to 12mg weekly. One shot, under the skin, same day each week. The drug is not yet FDA-approved - most US users get compounded versions through telehealth. Always with a doctor.

Route: subcutaneous injection. Evidence tier for the dose: RCT (late-stage). Late-stage human trials are reporting; FDA review pending. Real evidence, near-final.

The dose at a glance

What's typical What's the max in research
Starting dose: 2 mg subQ (under-the-skin shot) once weekly for the first 4 weeks. Some prescribers start at 1 mg if the patient is sensitive to GLP-1 side effects. Max observed in research: 12 mg weekly was the highest dose in published Phase-2 trials. No FDA-approved max yet (drug is pre-approval).
Maintenance dose: Most users in TRIUMPH-1 settled between 4 mg and 12 mg weekly. The 8 mg and 12 mg arms produced the most weight loss.
Frequency: Once weekly. Same day each week. Half-life: About 6 days. Once-weekly works for the same reason it does with Tirzepatide.

Titration (how to ramp the dose)

Trial titration ladder: 2 mg for 4 weeks -> 4 mg for 4 weeks -> 8 mg for 4 weeks -> 12 mg max. Some compounded protocols use a slower 4-week-per-step ladder ending at 8 mg unless tolerance is excellent.

Cycle length and time off

On cycle: Indefinite for chronic obesity or diabetes (assuming approval). Some users do 6 to 12 months for a defined goal.

Off cycle: Same as Tirzepatide - no required off cycle. Appetite returns over weeks to months without it.

Timing notes: Time of day does not matter. Most users inject morning of their chosen day. Inject in stomach, thigh, or upper arm fat. Rotate sites week to week.

What's commonly prescribed (per published protocols and clinical write-ups)

Retatrutide is not yet FDA-approved (as of 2026-05). Pre-approval access exists only through clinical trials or compounded versions from US compounding pharmacies. Compounded retatrutide ships in mg/mL concentration vials (commonly 10 mg/mL) - patient draws their own dose. Telehealth providers (Hims, Henry Meds, Mochi) began offering compounded versions in 2025 ahead of approval. Quality varies - always ask for a COA (Certificate of Analysis, the lab purity test result).

Source: prescribing labels, published protocols, and clinical write-ups. We have not independently tested each prescriber pattern.

Reconstitution (mixing the vial)

Compounded retatrutide ships pre-mixed in liquid form (no reconstitution needed) at a labeled concentration like 10 mg/mL. At 10 mg/mL, 0.4 mL on the syringe equals 4 mg. Store in fridge. If your pharmacy filled the vial with a different volume, recalculate from the mg/mL printed on your vial label - not from this page. Throw out at the expiration printed on the vial.

Reconstitution = mixing freeze-dried (lyophilized) powder with bacteriostatic water (sterile water with preservative) so you can draw a dose into a syringe.

Drug interactions to watch

  • Slows gastric emptying (like all GLP-1s) - separate oral medications by at least 1 hour.
  • Birth control: efficacy may be reduced during titration and after dose increases. Use backup.
  • Insulin and sulfonylureas: high hypoglycemia risk if combined - prescriber should adjust those down.
  • The glucagon-receptor component is novel - report any unusual symptoms.

Who should not take this (contraindications)

  • Personal or family history of medullary thyroid carcinoma (a rare thyroid cancer; class effect for incretin drugs).
  • Multiple Endocrine Neoplasia syndrome type 2.
  • Active pancreatitis.
  • Pregnancy and breastfeeding (stop at least 2 months before trying to conceive).

Common side effects

  • Nausea (more pronounced than Tirzepatide in trials, especially in titration).
  • Constipation or diarrhea.
  • Burping, reflux.
  • Fatigue in the first week of each new dose.
  • Injection-site reaction (mild redness, itch).

Serious side effects (call a doctor)

  • Pancreatitis (severe persistent stomach pain that radiates to the back) - go to ER.
  • Gallbladder problems including stones (more common during rapid weight loss).
  • Severe dehydration from GI side effects.
  • Diabetic retinopathy worsening in pre-existing diabetics.
  • Allergic reaction including face swelling (rare).

What to monitor while you're on it

  • Weight and waist measurement weekly for the first 12 weeks.
  • A1C and fasting glucose at baseline and every 3 months if diabetic.
  • Lipid panel and liver enzymes every 6 months (the liver-fat effect makes baseline ALT/AST useful).
  • Body composition scan (DEXA or InBody) at start and 6 months.

How to stop

No formal taper. Step down a dose level for 4 weeks before stopping for a softer landing. Lock in protein and resistance training during that step-down.

Where this dosing comes from

  • TRIUMPH-1 trial (NEJM, 2023) - Phase 2 obesity
  • TRIUMPH NASH Phase 2 (2024)
  • Eli Lilly clinical trial protocols and dose-finding work
  • US compounding pharmacy protocols (pre-approval, 2025-2026)

Where these doses come from

These doses come from late-stage human trials in the TRIUMPH trial program and pre-approval clinical use. Not yet FDA-approved at this exact dose, but supported by published trial data.

Always work with a real prescriber. Don't self-prescribe.

Safety reminder: None of this replaces a doctor. Peptides are gray-market in the US for most uses. Talk to a real prescriber before you change anything.

Where to go next

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Last reviewed · 2026-05-07 · Page generated by Protocol One matrix engine. None of this replaces a doctor. Peptides are gray-market in the US for most uses. Talk to a real prescriber before you change anything.