Enter your vial size and BAC water — get the exact syringe units to draw for any titration stage. Includes the standard 2mg → 4mg → 8mg → 12mg protocol.
28.7%Avg weight loss in Phase 3
6 daysHalf-life (weekly injection)
3×Receptor agonist (GLP-1, GIP, Glucagon)
+512%Search growth YoY 2026
Retatrutide Reconstitution Calculator
Vial size
mg on your label (common: 5mg, 10mg, 12mg)
mg
BAC water added
Bacteriostatic water volume
mL
Your dose
e.g. 2 mg for Tier 1, 12 mg for maintenance
mg
Unit
Syringe type
Result
Fill Your Syringe To Here
—
TierDose/wkUnits to drawmL per doseDoses in vial
—
mg/mL concentration
—
mL per injection
—
doses at this tier
For reference only. This tool performs mathematical conversions. It is not medical advice. Retatrutide dosing should be managed by a licensed healthcare provider.
The Drug
What Is Retatrutide? (LY3437943)
Retatrutide is an investigational peptide drug developed by Eli Lilly. It is a triple agonist — meaning it activates three hormone receptors simultaneously: GLP-1, GIP, and Glucagon. Most weight loss drugs currently approved only target one or two of these receptors. Tirzepatide (Mounjaro/Zepbound) targets two. Retatrutide targets all three.
Phase 3 clinical trial results showed average body weight reduction of 28.7% at 96 weeks — the highest ever recorded for a weight-loss drug. For context, bariatric surgery typically produces 25–30% weight loss. FDA approval is expected in late 2026 to early 2027 pending trial completion.
Generic name
Retatrutide (LY3437943)
Developer
Eli Lilly & Company
Mechanism
Triple agonist — GLP-1 + GIP + Glucagon
Phase 3 weight loss
28.7% avg at 96 weeks
Half-life
~6 days (once weekly injection)
Steady state
~4–5 weeks at consistent dosing
Administration
Subcutaneous injection, once weekly
FDA status
Phase 3 trials — approval est. 2026–2027
Dosing Protocol
Standard Retatrutide Titration Protocol
Retatrutide uses a gradual dose escalation schedule. Starting low and increasing slowly over weeks minimizes gastrointestinal side effects — the most common complaint with GLP-1 class drugs — while allowing your body to adjust to the medication.
The standard protocol from Phase 3 trials increases the dose every 4 weeks. Most people reach the maintenance dose of 12mg after about 12–16 weeks. Some providers use a slower titration for better tolerability.
Tier
Weekly Dose
Duration
Purpose
T1
2 mg
4 weeks
Initial tolerance phase
T2
4 mg
4 weeks
Escalation — appetite suppression begins
T3
8 mg
4 weeks
Therapeutic range — significant weight loss begins
T4
12 mg
Maintenance
Maximum studied dose — sustained weight loss
Some protocols include an intermediate 6mg dose between T3 and T4. Your provider may adjust the schedule based on your tolerance and response. The calculator above supports any dose — just type in your current dose value.
Step by Step
How to Reconstitute Retatrutide
Retatrutide comes as a lyophilized (freeze-dried) powder that must be mixed with bacteriostatic water before injection. Common vial sizes are 5mg, 10mg, and 12mg.
What you need
Retatrutide vial (lyophilized powder), bacteriostatic water (BAC water), insulin syringe (U-100, 1mL), alcohol swabs, sterile gloves, and refrigerator storage.
The reconstitution steps
1. Wash hands thoroughly and put on gloves. Wipe both the retatrutide vial stopper and the BAC water vial stopper with alcohol swabs. Let dry for 30 seconds.
2. Draw your chosen volume of BAC water into an insulin syringe. A common ratio is 2mL per 10mg vial — this gives you 5mg/mL concentration, making dose math simple. Your provider may specify a different ratio.
3. Inject the BAC water slowly down the inner glass wall of the retatrutide vial. Do not spray directly onto the powder. Do not shake — gently swirl until the powder is completely dissolved and the liquid is clear.
4. Use the calculator above to find your exact draw volume. Enter your vial size, how much BAC water you added, and your current dose. Draw exactly that many units on your syringe.
5. Store reconstituted retatrutide in the refrigerator at 36–46°F (2–8°C). Protect from light. Most reconstituted peptides remain stable for 28–30 days. Discard if the solution becomes cloudy or discolored.
Common vial concentrations
The most common combinations and their resulting concentrations:
Vial Size
BAC Water
Concentration
2mg dose =
10mg
1mL
10mg/mL
0.2mL / 20 units
10mg
2mL
5mg/mL
0.4mL / 40 units
10mg
4mL
2.5mg/mL
0.8mL / 80 units
5mg
1mL
5mg/mL
0.4mL / 40 units
12mg
2mL
6mg/mL
0.33mL / 33 units
FAQ
Retatrutide — Common Questions
Semaglutide (Ozempic/Wegovy) is a single agonist — it only activates the GLP-1 receptor. Tirzepatide (Mounjaro/Zepbound) is a dual agonist targeting GLP-1 and GIP receptors. Retatrutide is a triple agonist targeting all three: GLP-1, GIP, and Glucagon. Each additional receptor target produces greater metabolic effects. Phase 3 data shows retatrutide producing roughly 28.7% weight loss versus ~20% for tirzepatide and ~15% for semaglutide at comparable timepoints.
No — as of mid-2026, retatrutide is not FDA approved. It is in Phase 3 clinical trials. FDA approval is estimated for late 2026 to early 2027 based on current trial timelines. It cannot be legally prescribed outside of approved clinical trials in the US. Compounded versions exist but are not FDA-approved formulations.
Retatrutide has a half-life of approximately 6 days. This means after 6 days, about 50% of your last dose remains active in your system. This is why it's dosed once weekly — there's still meaningful drug present when you take the next dose. After 4–5 weeks of consistent weekly dosing, you reach "steady state" — where the amount entering your system each week equals the amount being cleared. Most people notice increased efficacy after reaching steady state at each titration tier.
There is no single correct answer — it depends on your dose and syringe. The most common choice is 2mL per 10mg vial (giving 5mg/mL concentration), because it puts most common doses in a comfortable range of 20–80 units on a standard insulin syringe. If your dose is very small (e.g., 2mg), using less BAC water (1mL) makes measuring easier. If you're on 8–12mg, more water (2mL+) spreads the volume into a more manageable draw. Use the calculator above to model different scenarios before reconstituting.
Compounded retatrutide typically comes in 5mg, 10mg, and 12mg vials, though some suppliers offer other sizes. Always check the label on your specific vial — never assume the size. Enter whatever your actual label says into the calculator. The calculator works with any vial size.
No. Each injection should use a fresh, sterile syringe. Reusing syringes risks contamination of your vial and infection at the injection site. Insulin syringes are inexpensive — buy a box and use one per injection. You can draw from the same vial multiple times (the bacteriostatic water preservative makes this safe), but always use a new syringe each time.
No. This tool performs mathematical conversions only. It takes the numbers you enter and calculates the equivalent volume and syringe units. It does not recommend doses, evaluate your health, or replace guidance from a licensed healthcare provider. Your specific dose, titration schedule, and injection protocol should come from the provider who is managing your retatrutide use.
Coming Soon
Find a Verified Retatrutide Clinic
We're building a vetted directory of licensed clinics offering retatrutide and other peptide therapies. Be first to know when we launch.
No spam. One email when we launch.
🎉
You're on the list!
We'll email you when verified retatrutide clinics go live in your area.