Retatrutide Dosage Guide: How Much, How Often & For How Long

Retatrutide is the newest of the weight-loss injectables and has no FDA label yet, so there is no official schedule. What people use is copied from the published phase 2 and phase 3 trial designs: start at a low weekly dose, add a step every four weeks, and settle somewhere between 4 and 12 mg. Because it is unapproved, the community leans more conservative on the starting dose than the trials did.

At a glance

Typical dose: Start 1–2 mg weekly; trial doses 4, 8–9 and 12 mg weekly (12 mg max studied)
How often: Once a week, same day each week
Route: Subcutaneous — abdomen, thigh or upper arm
Timing: Any time; no label rules exist, so the tirzepatide conventions are borrowed
How long: Continuous; 4 weeks per step is the trial pattern
Vial sizes: 10 mg, 30 mg and 50 mg

How much

The phase 2 trial (48 weeks) tested 1, 4, 8 and 12 mg weekly. The higher groups started at 2 mg (some at 4 mg) and stepped up every four weeks: 2 → 4 mg, 2 → 4 → 8 mg, or 2 → 4 → 8 → 12 mg. Starting at 4 mg caused more early stomach side effects with no better result at 48 weeks — which is why a 2 mg start became the convention.

The phase 3 TRIUMPH program tested 4, 9 and 12 mg weekly. The community typically starts at 2 mg (1 mg, or even 0.5 mg, for a cautious start), rises every four weeks — commonly 2 → 4 → 6 or 8 → 9 → 12 mg — and stops at the lowest dose that works. The practical range is 2–12 mg, with 4–8 mg the most common landing zone.

Step	Dose	Notes
Weeks 1–4	2 mg (1 mg for a cautious start)	4 weeks; some sources hold the first step 8 weeks
Weeks 5–8	4 mg	4 weeks — the lowest phase 3 dose
Weeks 9–12	6–8 mg	4 weeks
Weeks 13–16	8–9 mg	4 weeks — a common stopping point
Week 17 on	12 mg	Maximum dose studied

How often & when

Once a week, same day each week. There is no label, so there is no official food or missed-dose rule; the community borrows tirzepatide’s: take a missed dose within 4 days, otherwise skip it, and never double up.

Abdomen, thigh and upper arm are used, rotating sites.

How long

Continuous in the trials (80 weeks in TRIUMPH-1, with a longer extension). Community sources expect regain after stopping, and some suggest stepping down one dose every four weeks rather than stopping abruptly — that idea has no trial basis.

Mixing the vial

Doses below are for a standard U-100 insulin syringe (100 units = 1 mL). The formula: units = dose in mg ÷ concentration in mg/mL × 100. Bacteriostatic water is the usual diluent. A standard peptide vial holds about 3 mL of liquid at most — the store’s vials included — so every row below stays at or under 3 mL. Guides elsewhere that call for 4–5 mL will not fit.

Vial	Water added	Concentration	Doses in units
10 mg	2 mL	5 mg/mL	0.5 mg = 10 u · 1 mg = 20 u · 2 mg = 40 u · 4 mg = 80 u
10 mg	1 mL	10 mg/mL	1 mg = 10 u · 2 mg = 20 u · 4 mg = 40 u · 8 mg = 80 u
30 mg	3 mL	10 mg/mL	2 mg = 20 u · 4 mg = 40 u · 8 mg = 80 u · 12 mg = 120 u (two draws)
30 mg	1.5 mL	20 mg/mL	4 mg = 20 u · 8 mg = 40 u · 12 mg = 60 u
50 mg	3 mL	16.7 mg/mL	6 units per mg: 2 mg = 12 u · 8 mg = 48 u · 12 mg = 72 u
50 mg	2.5 mL	20 mg/mL	5 units per mg: 2 mg = 10 u · 12 mg = 60 u

Pick the vial size to match your dose: the 10 mg vial suits the first month, the 30 and 50 mg vials the higher steps. At 10 mg/mL, 1 mg is 10 units — one guide circulating online says 100 units per mg, which is wrong by a factor of ten.

How to reconstitute

Not sure how to mix the vial? Our free Reconstitution Calculator walks you through it: enter the vial size, how much bacteriostatic water you're adding and the amount you want per dose, pick your syringe, and it tells you exactly what mark to draw to, the concentration, and how many doses the vial holds — with a syringe diagram and a step-by-step worked example.

Practical tips

Stomach side effects track both the dose and the starting dose. Starting at 2 mg or lower and climbing slowly is the main mitigation.
Add the water slowly down the inside of the vial, do not shake, refrigerate at 2–8 °C, and use within about 28–30 days.
Some clinic pages suggest baseline and per-step lab checks (liver, kidney, lipase, thyroid) because the compound is still in trials.
Research-grade retatrutide is not a pharmaceutical product; a batch-matched COA is the only way to know what is in the vial.

What the evidence looks like

Evidence level

Moderate. The phase 2 results are published (NEJM, 2023) and phase 3 TRIUMPH results have been reported, but there is no approved label. Every self-dosing and mixing figure here is community convention modeled on the trial schedules.

For what the compound is and how it is studied — mechanism, research history and the primary literature — read the reference entry: Retatrutide.

Batch-tested with published COAs

Retatrutide on the store

Every vial is tested by an independent lab, with a batch-linked certificate of analysis you can check before you buy. This page is educational; purchasing happens on the store.

Retatrutide 10mg Retatrutide 15mg Retatrutide 30mg Retatrutide 50mg Retatrutide COAs

Common questions

What is the usual retatrutide starting dose?

2 mg once a week is the most-cited start; 1 mg (or 0.5 mg) for a more cautious approach. The trials mostly started at 2 mg.

How many units is 2 mg?

40 units at 5 mg/mL (10 mg + 2 mL), 20 units at 10 mg/mL (10 mg + 1 mL or 30 mg + 3 mL), 10 units at 20 mg/mL.

What is the highest dose?

12 mg a week is the highest dose studied in the trials. Nobody cites more.

Sources

The figures above were compiled from the following pages. Where an FDA label exists it is listed first; the rest are vendor, clinic and community dosing references, which are not peer-reviewed.

NEJM — Retatrutide phase 2 obesity trial (Jastreboff et al., 2023) — Dose groups 1/4/8/12 mg, 4-week escalation steps, 48-week results Open
Healio — phase 2 results summary — Weight loss by dose; 2 mg start reduced GI side effects vs 4 mg Open
Pharmacy Times — TRIUMPH-1 phase 3 results — Phase 3 doses 4 / 9 / 12 mg weekly, 80 weeks Open
Form Blends — retatrutide starting dose — 2 → 4 → 8 → 12 mg every 4 weeks; 1 mg and 8-week-first-step variants Open
GLP3 Planner — retatrutide reconstitution guide — 10 mg + 2 mL = 5 mg/mL; 30 mg + 3 mL = 10 mg/mL Open
SeekPeptides — retatrutide reconstitution chart — 30 mg + 1.5 or 3 mL unit tables; 2 mg (or 1 mg) start Open

General information, not medical advice. This guide summarizes dosing conventions reported in published research and commonly cited across the peptide community. It is not a recommendation for any individual, it does not replace a licensed healthcare provider, and individual responses vary. Products sold by Midwest Compounds are labeled for research use.

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