Retatrutide Dosage Chart.
Retatrutide (LY3437943) is a once-weekly triple agonist: it activates the GLP-1, GIP and glucagon receptors at once, and that third receptor is why its phase 2 weight figures run ahead of everything else published. Every dose on this chart is a dose Eli Lilly actually administered in a trial. None of them is approved by any regulator.
2 mg once weekly for weeks 1–4, then 4, 8 or 12 mg , four weeks a step. Mixed at 10 mg in 1 mL of bacteriostatic water you have 10 mg/mL, so 1 unit on a U-100 syringe is 0.1 mg: 2 mg = 20 units, 4 mg = 40, 8 mg = 80. 12 mg is 120 units and overflows a 1 mL syringe. Approved by no regulator.
This chart is the condensed version. For the full write-up (mechanism, sourcing, stacking and the rest), read the full Retatrutide dosing guide.
Dosage Protocols
Units assume a 10 mg vial reconstituted with 1 mL bacteriostatic water = 10 mg/mL, so 1 unit on a U-100 syringe = 0.1 mg. Different setup? Use the calculator. Every milligram figure below is a real trial dose.
A ramp step, not a destination: 2 mg has never been tested as a maintenance dose.
Why this dose+
Its place here is inferred from the 1 mg arm, which reached -7.2% at 24 weeks: real, but well below what the higher arms produced. This month exists so the doses that do the work are tolerable by the time you reach them.
The lowest dose with a large effect: -17.1% at 48 weeks. Many people never need more.
Why this dose+
Both a phase 2 arm and a phase 3 arm sit here: -17.1% of body weight at 48 weeks in the phase 2 obesity trial, and -11.5% over 40 weeks of monotherapy in the phase 3 diabetes trial. It is the best-evidenced place to stop climbing.
Both are trial doses, but 12 mg is the highest ever given to a human: a ceiling, not a target.
Why this dose+
8 mg reached via a 2 mg start came in at -21.7% at 48 weeks; 12 mg reached -24.2%. At 10 mg/mL a 12 mg dose is 120 units, more than one 1 mL syringe holds, so mix more concentrated or split it across two injections.
- Both phase 2 groups finished on the same 8 mg, reached from different starting doses.
- Ramped from 2 mg: -21.7% at 48 weeks. Started cold at 4 mg: -23.9%.
- So the slow ramp costs about 2 points of weight loss, and is far easier to tolerate.
- The four weeks at 2 mg are a trade, not a formality.
- At 48 weeks the pooled 8 mg groups lost 22.8% and the 12 mg group 24.2%.
- That is 1.4 points for the highest dose ever given to a human.
- The weight-loss curve is flattening by 8 mg; the dose ladder is not.
- Treat 12 mg as the ceiling of the tested range, not the goal of the ramp.
Weekly Schedule
Every tier is the same shape: one injection, one day a week. What changes between them is the number in the syringe, not the pattern.
One injection, one day a week, at whatever time suits you, with or without food. With a half-life near 6 days the drug never fully clears between doses, so a missed week is skipped rather than doubled up.
Retatrutide Reconstitution Calculator
Enter your vial size, the water you added, and the dose you want. A 10 mg vial with 1 mL of bacteriostatic water gives 10 mg/mL, which puts a 4 mg dose at 40 units on a U-100 syringe. Dial in 12 mg on that mix and the calculator flags the overflow: 120 units does not fit in a 1 mL barrel.
Double-click a preset to edit it
Double-click a preset to edit it
Double-click a preset to edit it
Standard insulin syringe
Concentration
10.00 mg/mL
1 unit = 100 mcg
Draw volume
0.400 mL
= 4.00 mg ÷ 10.00 mg/mL
Units to draw (1 mL syringe)
40.0 units
1 mL Syringe
40.0 IUFrom Vial to Injection in 6 Steps
Alcohol swab the retatrutide vial and the bacteriostatic water vial, and let both air-dry before you pierce them.
Run the bacteriostatic water down the inside wall of the 10 mg vial. Never squirt it directly onto the powder cake. One millilitre into a 10 mg vial gives 10 mg/mL, which is the concentration every unit count on this page assumes.
Roll the vial gently until the solution is completely clear. Shaking damages the peptide, and there is no reason to rush a step that takes thirty seconds.
Use a fresh U-100 insulin syringe and the calculator. At 10 mg/mL, 2 mg is 20 units, 4 mg is 40 units and 8 mg is 80 units.
Subcutaneous into the abdomen, thigh or the back of the upper arm, rotating sites and staying clear of the navel, scar tissue and bruises. Time of day does not matter and neither does food; only the day of the week matters, and only because consistency does.
Keep the sealed vial at 2–8 °C, protected from light, and never freeze the mixed solution. Once reconstituted, refrigerate it and treat about 30 days as the outside limit. That figure is convention rather than data; no stability study for reconstituted retatrutide has ever been published. Needles go in a sharps container.
A 10 mg vial mixed at 1 mL is five doses at 2 mg, two and a half at 4 mg, or one dose plus a remainder at 8 mg. Nobody has published a stability study on reconstituted retatrutide, so the roughly 30-day mixed window is borrowed convention rather than measurement.
What to Expect
These are averages from the phase 2 obesity trial and the phase 3 diabetes trial: supervised participants, dietitian contact and drug of guaranteed purity.
Most people notice reduced hunger and smaller portions within the first few days at 2 mg. The scale barely moves in this window, and that is expected. Any nausea usually arrives in the 24–48 hours after the injection and settles well before the next one is due.
Nobody has measured what 2 mg does as a maintenance dose; the nearest reference point is the 1 mg arm, which reached -7.2% at 24 weeks. Real, but a long way below the higher arms. This month exists so the doses that follow are tolerable.
At week 24 the phase 2 groups averaged -12.9% (4 mg), -17.3% (8 mg) and -17.5% (12 mg) against -1.6% on placebo. Note that 8 mg and 12 mg are essentially indistinguishable at this point. The dose-dependent heart-rate increase also peaks around here, then declines over the following months.
Phase 2 finished at -17.1% (4 mg), -22.8% (pooled 8 mg) and -24.2% (12 mg) versus -2.1% on placebo. A loss of 15% or more was reached by 75% of the 8 mg group and 83% of the 12 mg group, against 2% on placebo. In the phase 3 diabetes trial, 40 weeks of monotherapy produced -11.5% (4 mg), -13.9% (9 mg) and -15.3% (12 mg).
Phase 2 stopped at 48 weeks. The phase 3 obesity trials run to 80 weeks and completed in April 2026, but no results have been published yet. Two-year outcomes, weight regain after stopping and long-term safety are unmeasured for this drug.
Two caveats. None of those numbers was produced by reconstituting lyophilised powder at home, and the ramp moves them: the slow-ramped phase 2 arms finished about one and a half to two percentage points lower than the cold-start arms at the same final dose.
Feeling Something? Check Here
- Mild nausea in the 24–48 h after the shot.
- Feeling full much earlier at meals.
- Noticeably quieter food cravings.
- Stools looser or firmer for a few days after a step-up.
- Slight pinkness at the injection site.
- Mild fatigue in the first fortnight.
- Vomiting more than once per dose.
- Resting heart rate up more than 10 bpm and staying there.
- Unable to keep fluids down for a day.
- Light-headedness on standing.
- Losing more than 1% of body weight per week.
- Constipation lasting beyond a week.
- Rapid muscle or strength loss.
- Severe unrelenting upper-abdominal pain radiating to the back (possible pancreatitis).
- Persistent vomiting with signs of dehydration.
- Right-upper abdominal pain with fever or yellowing skin (gallbladder).
- A new lump in the neck, hoarseness or difficulty swallowing.
- Sudden vision changes if you have diabetic retinopathy.
- Swelling of the face, lips or throat, or difficulty breathing.
Retatrutide has no approved label anywhere, so no official contraindication list exists. The stops below are carried across from the closest approved drug in its class, tirzepatide (ZEPBOUND), which has a boxed warning for thyroid C-cell tumours.
- Personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
- A serious hypersensitivity reaction to any GLP-1 or GIP agonist.
- Pregnant, trying to conceive, or breastfeeding.
- Already taking another GLP-1 or GIP agonist.
- Under 18.
- A history of pancreatitis or gallbladder disease.
- Gastroparesis or another significant gastrointestinal motility disorder.
- Type 1 diabetes.
- Diabetic retinopathy: the tirzepatide label flags worsening with rapid glucose improvement.
- Any condition that makes dehydration dangerous; that label ties acute kidney injury to vomiting and diarrhoea.
- An uncontrolled tachyarrhythmia, given the dose-dependent heart-rate rise measured in phase 2.
- Any history of suicidal ideation, which the label asks prescribers to monitor for.
- Oral contraceptives: delayed gastric emptying reduces their effectiveness.
- The tirzepatide label advises a non-oral or added barrier method for four weeks after starting and after each dose increase.
- Anaesthesia: tell the anaesthetist or endoscopist before a procedure, since delayed gastric emptying raises aspiration risk.
- Insulin and sulfonylureas: adjust those doses before you start.
FAQ
Is retatrutide FDA approved?+
No. It is not approved by the FDA or by any other regulator. It has 12 entries in the FDA's National Drug Code directory and every single one is classified BULK INGREDIENT: raw chemical registered by suppliers such as Nanjing Chengong and Qingdao Biopeptek, not a finished medicine. A phase 3 diabetes trial was published in The Lancet in June 2026 and the phase 3 obesity programme completed in April 2026, so a regulatory filing is plausible. Nothing has been approved yet.
How many units is my dose?+
It depends entirely on how much water you added, which is why any unit figure is meaningless without the mix stated next to it. At 10 mg of powder in 1 mL of bacteriostatic water you have 10 mg/mL, so 1 unit on a U-100 syringe is 0.1 mg: 2 mg is 20 units, 4 mg is 40 units, 8 mg is 80 units. 12 mg would be 120 units, which is more than a 1 mL syringe holds; at that dose you either use a more concentrated mix or accept two injections. Adding 2 mL instead of 1 mL halves the concentration and doubles every unit count.
Why does retatrutide have a third receptor, and does it change how I dose it?+
Retatrutide activates the glucagon receptor alongside GLP-1 and GIP. The glucagon arm is what raises energy expenditure rather than only cutting intake, and it is the plausible reason its weight numbers run ahead of the dual agonists. It is also why heart rate rose in a dose-dependent way in phase 2, peaking at week 24 before declining. Practically: do not assume a milligram of retatrutide behaves like a milligram of tirzepatide, and watch resting heart rate more closely than you would on a pure GLP-1 drug.
What if I miss a week?+
The half-life is about 6 days, so one missed dose does not reset your progress; you still have meaningful drug on board. There is no retatrutide label to tell you what to do, so the rule everyone uses is borrowed from tirzepatide: take the missed dose if you are within 4 days (96 hours) of when it was due, otherwise skip it and resume on your normal day. Never take two doses to catch up, because side effects track peak concentration and doubling up is how people end up vomiting. If you have missed several weeks, treat it as a restart and step back down the ladder rather than resuming at your old dose.
Can I escalate faster than four weeks per step?+
You can, and the posted trial results tell you what it costs in both directions. Participants who went straight to 4 mg instead of spending a month at 2 mg reported roughly three times the nausea at the same eventual dose (21 of 35 against 6 of 35 in the 8 mg groups). They also finished slightly ahead on weight: -23.9% versus -21.7% at 48 weeks. So a fast ramp is not simply worse, it is a harder first six weeks in exchange for about two percentage points. The phase 3 programme did not rush it either: TRIUMPH uses a fixed 16-week escalation period before maintenance dosing begins. If you have never used an incretin drug, the slow ramp is still the sensible default, because a couple of points are worth nothing if you quit in week five.
Is 12 mg worth it over 8 mg?+
For most people no, but the comparison has to be stated precisely. Against the pooled 8 mg groups, 12 mg added 1.4 percentage points at 48 weeks (24.2% versus 22.8%) while nausea went from 27 of 70 (39%) to 28 of 62 (45%). Against an 8 mg group ramped in slowly from 2 mg, 12 mg adds about 2.5 points (24.2% versus 21.7%) and takes nausea from 17% to 45%. Either way the weight-loss curve is flattening while the side-effect curve is not. 12 mg is a legitimate dose (a phase 2 arm and a phase 3 arm), but it is a ceiling rather than a target, and if you are still losing steadily at 4 or 8 mg the dose is not what is limiting you.
How should I store it?+
Keep the sealed lyophilised vial cold and protected from light. Once you add water, refrigerate it and treat about 30 days as the outside limit. Be clear that this is convention rather than data: no manufacturer stability study exists for reconstituted retatrutide of any kind. The 30 days comes from the benzyl-alcohol preservative in bacteriostatic water and from the in-use windows on the multi-dose GLP-1 products that do exist (30 days for liraglutide, 56 days for semaglutide). Tirzepatide, the closest molecule, is sold only in single-dose vials and pens, so it offers no beyond-use window to borrow. Do not freeze reconstituted solution and do not shake it; swirl gently. Discard anything cloudy, discoloured or containing particles.
How does it compare with semaglutide or tirzepatide?+
Retatrutide's 48-week phase 2 figure of -24.2% at 12 mg is the highest published for any drug in this space, but that is a cross-trial comparison between different populations, durations and protocols, not a head-to-head. Two direct comparisons are running and neither has reported. NCT06662383 puts retatrutide against tirzepatide in obesity with weight endpoints; that is the one that will actually settle this question. NCT06260722 puts it against semaglutide in type 2 diabetes on metformin with glycaemic endpoints, which will not. Treat any specific 'retatrutide beats tirzepatide by X%' claim as unproven until the first of those reads out.
Sources
The doses have human data behind them: phase 1 pharmacokinetics, a 338-person phase 2 obesity trial run to 48 weeks, and a 537-person phase 3 in type 2 diabetes published in June 2026. No regulator has approved it, the phase 3 obesity results are unpublished, and reconstituted lyophilised powder has never been studied.
- ·Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial. N Engl J Med 2023;389:514-526. PMID 37366315: 338 adults with obesity, 48 weeks; the source of the -17.1% / -22.8% / -24.2% figures and the responder rates.
- ·ClinicalTrials.gov NCT04881760: the phase 2 record with posted results, including adverse events and weight change broken out by starting-dose sub-arm (8 mg from a 2 mg start -21.72% vs -23.88% from a 4 mg start; 4 mg -16.32% vs -17.83%).
- ·Urva S et al. LY3437943, a novel triple GIP, GLP-1 and glucagon receptor agonist in people with type 2 diabetes: a phase 1b multiple-ascending dose trial. Lancet 2022;400:1869-1881. PMID 36354040. The source of the ~6-day half-life.
- ·Bajaj HS et al. Retatrutide in type 2 diabetes inadequately controlled with diet and exercise (TRANSCEND-T2D-1): a phase 3 trial. Lancet 2026;407:2402-2413. PMID 42250575: 537 participants; the source of the 40-week -11.5% / -13.9% / -15.3% monotherapy figures.
- ·Giblin K et al. Rationale and design of the TRIUMPH registrational trials. Diabetes Obes Metab 2026;28:83-93. The source of the phase 3 obesity doses (4, 9 and 12 mg) and the fixed 16-week escalation period.
- ·Coskun T et al. LY3437943, a novel triple glucagon, GIP and GLP-1 receptor agonist: from discovery to clinical proof of concept. Cell Metab 2022;34:1234-1247. PMID 35985340. The molecular identity and the receptor pharmacology behind the glucagon arm.
- ·FDA National Drug Code directory (openFDA): all 12 retatrutide entries are classified BULK INGREDIENT; there is no approved finished product.
- ·ZEPBOUND (tirzepatide) FDA label via DailyMed. The class analogue used for every safety statement on this page: boxed warning for thyroid C-cell tumours, the MTC/MEN 2 contraindications, and the warnings on pancreatitis, gallbladder disease, acute kidney injury, diabetic retinopathy, suicidal ideation, anaesthesia aspiration risk and reduced oral-contraceptive effectiveness. Note that it is supplied in single-dose vials and pens, so it carries no beyond-use window for a mixed multi-dose vial.
The longer treatment of all of this (sourcing, purity testing, stacking and how retatrutide compares with the dual agonists) lives in the full Retatrutide dosing guide.
Disclaimer: Informational purposes only; not medical advice. Retatrutide is not approved in any jurisdiction, and all 12 of its FDA drug-directory entries are registered as bulk chemical ingredient. Safety statements here come from the tirzepatide label. Doses come from Lilly's published trials; the four-weeks-per-step ladder, reconstitution volumes and storage windows are convention. Consult a qualified healthcare professional before starting any peptide protocol. PeptideDeck is not responsible for individual use.
