Reference protocol: Retatrutide
Retatrutide is dosed once per week. Our guideline starts lower than the international reference —1.5 mg— and advances in 0.5 mg steps, never in 2 mg jumps: fewer adaptation effects and a minimum effective dose found with precision.
The reference for retatrutide starts at 1.5 mg per week —15 units at 10 mg/ml— and increases in 0.5 mg steps, always on the same day of the week. With our 1-to-1 reconstitution, each 0.5 mg equals 5 units on a U-100 syringe.
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You have never used semaglutide, tirzepatide or similar: start at 1.5 mg.
First time? Start here
Your Retatrutide vial arrives with the compound as a dry powder. Before using it you mix it with a special water — that step is called reconstitution — and measure each dose with an insulin syringe. Here is everything you need, in order.
- Get what you need: your vial, a vial of bacteriostatic water (not included — it is the special mixing water), a 1 ml U-100 insulin syringe — ask for it exactly like that at any pharmacy — and alcohol wipes.
- Mix the powder with the water (reconstitute): the vial is never uncapped — the needle goes through the rubber stopper. Add 0.5 ml of water letting it run down the inside wall, then swirl gently — never shake; it turns clear in a few minutes (some compounds take longer). Measure the water with the same insulin syringe: fill it up to the 50 mark. Once mixed, the vial goes in the fridge and lasts about 4 weeks; unmixed, also keep it refrigerated from the day it arrives.
- Fill the syringe up to the 15 mark: every small line on the insulin syringe is 1 unit (U). That mark equals the starting dose (1.5 mg); if your dose is different, pick it in the panel below and the number updates. And note: several protocols raise the dose after the first weeks — the dose steps further down tell you when your mark changes.
- Inject under the skin and you are done: belly area (two fingers away from the navel), skin cleaned with alcohol; pinch the skin, insert the full needle and inject slowly. Switch sides each time and use a new syringe for every injection. Used once a week, on the day you choose — always that same day.
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Quick dictionary — the words that stop beginners
- Reconstitute: mixing the vial's powder with the special water so it becomes a liquid you can measure.
- Bacteriostatic water: the special water for that mix (regular water will not do); sold separately — one vial covers several mixes.
- Unit (U): each small line on the insulin syringe. 100 units = 1 ml.
- U-100 syringe: the standard 1 ml insulin syringe with 100 marks; sold at any pharmacy.
- mg and mcg: milligrams and micrograms: 1 mg = 1,000 mcg. Mind the factor of one thousand when reading a dose.
- Subcutaneous: an injection under the skin (not into muscle or vein), usually in the belly area.
- Cycle and washout: using the product for a period and then stopping completely for some weeks; when resuming you start again from the starting dose.
Quick facts
| Parameter | Reference |
|---|---|
| Frequency | 1 dose every 7 days, always on the same day of the week |
| Time of day | Any; keep a consistent schedule |
| Fasting | Not required |
| Titration | Start at 1.5 mg · 0.5 mg increases (house guideline) |
| Cycle | Optional: 4 months of use and 4 of washout |
| Documented route | Subcutaneous injection |
Start low and titrate finely
International documentation for this compound usually starts at 2 mg per week and doubles from there. Our guideline is more conservative: start at 1.5 mg and always increase by 0.5 mg, evaluating the response before each increase. Anyone who has already been through titration with other GLP agonists can start one step higher, but the step size does not change.
Reconstitution and syringe units
House 1-to-1 rule: 5 mg → 0.5 ml · 15 mg → 1.5 ml · 30 mg → 3 ml — every presentation sits at 10 mg/ml.
The buttons follow the protocol's dose steps; the starting dose comes pre-selected.
Fill the syringe up to the 15 mark
The syringe: a 1 ml U-100 insulin syringe (100 small marks = 1 ml), sold at any pharmacy.
Open this calculation in the calculatorThe protocol week
See the full dose-to-units table
| Dose | U-100 syringe | Volume | Vial 5 mg | Vial 15 mg | Vial 30 mg |
|---|---|---|---|---|---|
| 1.5 mg | 15 U | 0.15 ml | 3 | 10 | 20 |
| 2 mg | 20 U | 0.2 ml | 2 | 7 | 15 |
| 2.5 mg | 25 U | 0.25 ml | 2 | 6 | 12 |
| 3 mg | 30 U | 0.3 ml | 1 | 5 | 10 |
| 4 mg | 40 U | 0.4 ml | 1 | 3 | 7 |
| 5 mg | 50 U | 0.5 ml | 1 | 3 | 6 |
| 6 mg | 60 U | 0.6 ml | — | 2 | 5 |
| 8 mg | 80 U | 0.8 ml | — | 1 | 3 |
| 10 mg | 100 U | 1 ml | — | 1 | 3 |
| 12 mg | 120 U | 1.2 ml | — | 1 | 2 |
Units refer to an insulin U-100 syringe (100 units = 1 ml). Tap a figure to open it in the calculator. The vial columns show how many complete doses each presentation yields; — means that vial does not cover one full dose.
A dose above 10 mg does not fit in a 1 ml syringe at 10 mg/ml. For that range, reconstitute the 30 mg vial with 2 ml instead of 3 —it comes to 15 mg/ml and 12 mg is 80 units— or split the draw in two. Check it in the calculator.
Reference titration
| Stage | Weekly dose |
|---|---|
| Start, no prior GLP experience | 1.5 mg |
| Start, with prior experience and titration on another GLP | 2 mg |
| Increases | +0.5 mg at a time, based on response |
| Range documented in research | up to 12 mg |
Each step is held as long as needed to evaluate the response before increasing; in documented practice with GLP agonists that means staying several weeks per dose, not week-to-week increases.
Documented precautions
- The most reported adaptation effects in this class are digestive: nausea, constipation or diarrhea, and reduced appetite. They tend to concentrate after each dose increase.
- Do not combine with other GLP agonists (semaglutide, tirzepatide): documented receptor redundancy and desensitization.
- GLP agonists delay gastric emptying: any procedure involving anesthesia must be informed of its use because of the risk of pulmonary aspiration.
- Contraindicated with a personal or family history of medullary thyroid carcinoma or MEN-2, and in pregnancy and lactation.
- Keep the reconstituted vial refrigerated (2–8 °C) and protected from light.
In our catalog
All three formats —5, 15, and 30 mg— are on the Retatrutide product page, with their per-batch certificate of analysis. If your protocol uses another dual agonist, check the Tirzepatide protocol.
Frequently asked questions
How much water do I reconstitute each vial with?
With the house 1-to-1 rule: the milligrams divided by 10. The 5 mg vial takes 0.5 ml; the 15 mg vial, 1.5 ml; the 30 mg vial, 3 ml. All three presentations come to 10 mg/ml, so the syringe units are the same with any vial.
How many units is 1.5 mg?
At 10 mg/ml, 15 units on a U-100 syringe (0.15 ml). The shortcut at this concentration: units = micrograms ÷ 100, or put another way, each 0.5 mg is 5 units.
Is the 5 mg vial enough to start?
It yields 3 complete doses of 1.5 mg: the first three weeks of the titration. The 15 mg vial yields 10 doses of 1.5 mg, and makes sense once you already know you will continue.
What if an interval stretches beyond 7 days?
Documented practice resumes at the same dose that was being used, without doubling it or moving the next increase forward. Consistency of the day of the week is part of the protocol.
Reference protocols compiled from documented research practice and adapted to our formats. Research-context documentation (RUO): not medical advice, not a prescription, and no substitute for professional evaluation.