Dosage guide · 10 mg and 20 mg vials

Retatrutide Dosage Protocol

LY3437943 · GIP / GLP-1 / glucagon triple agonist

Retatrutide is taken once weekly under the skin. The reference protocol starts at 2 mg and steps up every 4 weeks only if tolerated, to a studied maximum of 12 mg. Mix 1 mL of bacteriostatic water into the 10 mg vial (or 2 mL into the 20 mg vial) for 10 mg/mL — so 2 mg is 20 units on a U-100 syringe.

How oftenOnce weekly

Starting dose2 mg

Start = units20 units

Mix1 mL BAC water

Reviewed 25 Oct 2026 · Education only, not medical advice

Retatrutide 10 mg vial

View on Peak Peptides

Exact Peak Peptides Australia product photo

Dosage chart How to mix Supplies Calculator About Retatrutide References

01 · DOSAGE CHART

Retatrutide dosage chart

Gradual weekly approach · 10 mg vial + 1 mL BAC water

Vial

BAC water added

Concentration10 mg/mL

1 unit (U-100)100 mcg= 0.01 mL

How oftenOnce weeklySubcutaneous injection

1 mL in the 10 mg vial or 2 mL in the 20 mg vial both give 10 mg/mL, so 10 units = 1 mg and every step up to 9 mg fits in one syringe. Peak's 10 mg page also shows a 2 mL mix (5 mg/mL) — switch above to see those units.

Retatrutide dosage chart for a 10 mg vial mixed with 1 mL of bacteriostatic water
Week	Weekly dose	Syringe units
Weeks 1–4Start	2 mg	20 units0.2 mL
Weeks 5–8	4 mg	40 units0.4 mL
Weeks 9–12	6 mg	60 units0.6 mL
Weeks 13–16	9 mg	90 units0.9 mL
Week 17 onwardsMax	12 mg	120 units1.2 mL · 2 syringe drawsMore than one 10 mg vial — use the 20 mg vial

Once weekly · same day each week · subcutaneous injection

Step up only after at least 4 weeks on the current dose, and only if it is well tolerated. If side effects are bothersome, stay on the current step.

4 mg and 9 mg were also studied as ongoing doses — 12 mg is the maximum studied, not a dose everyone needs to reach.

Steps match the escalation used in Eli Lilly's phase 3 TRIUMPH trials. Retatrutide is not an approved medicine in Australia — education only, not medical advice. Dose amounts adapted from Retatrutide 10 mg vial dosage protocol (PeptideDosages.com); units are recalculated for the vial and mix selected above.

02 · HOW TO MIX

Mixing a 10 mg vial with 1 mL of BAC water

Using a 1 mL (100-unit) insulin syringe, one full draw of bacteriostatic water gives 10 mg/mL.

1
Add the water slowly
Wipe both rubber stoppers with an alcohol swab and let them dry. Draw 1 mL of bacteriostatic water and let it run slowly down the inside of the vial wall — not straight onto the powder.
2
Swirl gently
Swirl or roll the vial gently until the powder has dissolved. Give it a few minutes to settle if needed.
3
Don't shake it
Shaking can damage the peptide and cause foaming. Gentle swirling only.
4
Check it's fully clear
Only use it once it is fully clear with no particles. Label the vial with the date and 10 mg/mL, then store it in the fridge at 2–8 °C.

Full illustrated reconstitution guide

03 · SUPPLIES NEEDED

What you'll need

Counts follow the dosage chart above at the highest amount in each step, using a 10 mg vial mixed with 1 mL.

Length of protocol

3Retatrutide 10 mg vials24 mg needed in total

111 mL insulin syringesU-100, 27–31G · one per draw + one per vial mixed

1BAC water 10 mL bottle3 mL used for mixing

22Alcohol swabsSkin + stopper, every time

Plus an approved sharps container. Syringes and swabs are sold by Australian pharmacies — Peak Peptides and Pure Performance supply the bacteriostatic water.

Retatrutide 10 mg vialPeak Peptides Australia

Peak Peptides Australia Bacteriostatic water 10 mL

Bacteriostatic water 10 mLPeak Peptides Australia

Pure Performance Australia Bacteriostatic water 10 mL

Bacteriostatic water 10 mLPure Performance Australia

04 · CALCULATOR

Check a different amount

Enter your vial, water and dose to see the matching syringe units.

Concentration Calculator

Labelled Vial Amount (mg)

Verified Final Liquid Volume1 mL

Amount to Evaluate (not a recommendation)

Concentration

10.00 mg/mL

(10000 mcg/mL)

Calculated Liquid Volume

0.200 mL

Equivalent U-100 volume scale position

20markings (not biological IU)

Illustration of a U-100 volume scale, not preparation or injection guidance

05 · PROTOCOL DETAILS

About Retatrutide

Protocol overview

Starting dose: 2 mg once weekly
How it increases: Every 4 weeks if tolerated: 2 → 4 → 6 → 9 → 12 mg
Ongoing doses studied: 4 mg, 9 mg or 12 mg once weekly
Maximum studied: 12 mg once weekly
When to take it: Same day each week, any time of day
Common mix: 10 mg vial + 1 mL, or 20 mg vial + 2 mL → 10 mg/mL

Storage

Before mixing: Freezer (−20 °C) for long-term storage, sealed and away from light.
After mixing: Fridge at 2–8 °C, upright and dark. Peak advises using it within about 4 weeks.
Never: Freeze a mixed vial, or use one that is cloudy, discoloured or has particles.

How it works

Retatrutide (LY3437943) is a single molecule that activates three hormone receptors: GIP, GLP-1 and glucagon — which is why it's called a triple agonist.

GLP-1 and GIP signalling reduce appetite and improve blood-sugar control. Glucagon-receptor activity is thought to increase energy use and reduce liver fat.

Illustrated mechanism explainer

What the research shows

Phase 3 TRIUMPH-1 (2,339 adults, 80 weeks): average weight loss was 19.0% on 4 mg, 25.9% on 9 mg and 28.3% on 12 mg, compared with 2.2% on placebo. Everyone started at 2 mg and stepped up every 4 weeks via 2 → 4 → 6 → 9 mg to their target.
Phase 3 TRIUMPH-4 (445 adults with knee osteoarthritis, 68 weeks): 26.4% weight loss on 9 mg and 28.7% on 12 mg, with knee-pain scores down by about 75%.
Phase 2 obesity trial (NEJM, 2023): 24.2% average weight loss after 48 weeks on 12 mg. Starting at 2 mg instead of 4 mg reduced stomach side effects.
Approval status: not approved by the TGA or the US FDA. Eli Lilly has said it plans to apply for approval in early 2027, and retatrutide is legally available only inside its clinical trials.

Reported side effects

Nausea (28–42% across doses in TRIUMPH-1, versus 15% on placebo), diarrhoea, constipation and vomiting — mostly while the dose is being increased.
Reduced appetite, and skin-sensation changes (dysesthesia) in 5–21% depending on dose and trial.
A dose-related rise in resting heart rate, which peaked and then eased in the phase 2 trial.
Redness or irritation at the injection site.
Stopping because of side effects was more common at higher doses: 4.1% on 4 mg up to 11.3% on 12 mg in TRIUMPH-1 (4.9% on placebo).

Important notes

Not an approved medicine: retatrutide is still in clinical trials and is not on the Australian Register of Therapeutic Goods.
Fakes are common: Australian health authorities have warned about counterfeit 'retatrutide' that contained other drugs. Check the batch test report for your vial.
Medicines in the GLP-1 class carry warnings about pancreatitis and gallbladder problems. Talk to a doctor if you have a history of either.
Never use a mixed vial that is cloudy, discoloured or has particles in it.

Injection basics

Use a new sterile 1 mL (100-unit) U-100 insulin syringe, 27–31G, every time — never reuse or share.
Wipe the vial stopper and the skin with an alcohol swab and let both dry first.
Inject under the skin (subcutaneously) of the abdomen, thigh or upper arm, and rotate sites.
Put used syringes straight into an approved sharps container — the NDSS lists Australian disposal options.

Guidance: World Health Organization · National Diabetes Services Scheme (NDSS)

06 · QUICK ANSWERS

Retatrutide questions

How many units is 2 mg of retatrutide?

It depends on how much water you added. In a 10 mg vial, 2 mg is 40 units with 2 mL of water (5 mg/mL), 20 units with 1 mL (10 mg/mL), and 60 units with 3 mL.

How much BAC water do I add to retatrutide 10 mg?

1 mL gives 10 mg/mL (10 units = 1 mg), which keeps every step up to 9 mg inside one 1 mL syringe. Peak's guide also shows 2 mL, which gives 5 mg/mL (20 units = 1 mg). For the 20 mg vial, 2 mL gives 10 mg/mL. Use the selector above the chart to match your mix.

How often should the retatrutide dose go up?

In the trials, no sooner than every 4 weeks — not every week — and only if the current dose is well tolerated.

How long does a 10 mg vial last?

Five weekly doses at 2 mg, or two and a half doses at 4 mg. Higher steps use more than one 10 mg vial — Peak also lists a 20 mg vial.

07 · SOURCES