How do I calculate peptide concentration after adding water?

Divide the amount in the vial by the volume of water you added. A 10 mg vial mixed with 2 mL gives 10 ÷ 2 = 5 mg/mL, which is the same as 5,000 mcg/mL.

How many units are in 1 mL on a U-100 syringe?

A U-100 insulin syringe is marked so that 100 units equal 1 mL. Each unit is 0.01 mL, so 0.25 mL reads as 25 units.

How do I convert mg to mcg?

Multiply milligrams by 1,000. 1 mg = 1,000 mcg, so 0.25 mg = 250 mcg. To go back, divide mcg by 1,000.

Can I convert units on the syringe back to an amount?

Yes. Divide the units by 100 to get mL, then multiply by the concentration. 20 units = 0.20 mL; at 5 mg/mL that holds 1 mg. The calculator does this when you type units into the units box.

Does adding more water change how much is in the vial?

No. The total in the vial stays the same. More water lowers the concentration, so the same amount takes up more volume and more units on the syringe.

Why is IU treated differently from mg?

IU measures biological activity, not weight, so there is no universal IU-to-mg rule. The calculator uses the IU count printed on your own vial label instead of guessing.

Does PeptideWhiz suggest doses?

No. PeptideWhiz never suggests or recommends an amount. Every number comes from you, and the tool only does the arithmetic. It is not medical advice.

Do I need an account to use the calculator?

No. The calculator is free and works without an account. An account only lets you save results to your stack and tracker.

Peptide Calculator

Vial and water math for Retatrutide, with a research record of published human trials. Math only, no suggested amounts.

Free · no account needed

Compound (Optional)

Desired Amount Per Dose

units (U-100)

Vial Strength (Total mg of Your Vial)

Reconstitution Solution Added

Titration Schedule (Optional)

Results

Draw to

—units

Enter amount, vial and Reconstitution Solution

ConcentrationConc.

—mg/mL

Your dose

—mg

Doses / vial

—

More than 100 units (over 1 mL). This won't fit in a single U-100 syringe draw. Double-check your numbers or use more water / a smaller amount.

U-100 Syringe · 1 mL

Notes

PeptideWhizpeptidewhiz.app · research use only

Research use only (RUO). Results are math on the values you enter only, not a recommendation or prescription for human use. Not medical advice. Always verify your own measurements. Full disclaimer

About Retatrutide

Retatrutide (LY3437943) is an investigational single peptide that acts on three receptors: GIP, GLP-1 and glucagon. Adding glucagon receptor activity is the main difference from dual agonists such as tirzepatide, and researchers are studying whether it changes energy use and liver fat.

Research status

Retatrutide is not approved by the FDA or any other regulator. It is in late-stage clinical trials, and the human data so far come from clinical trials such as those listed below.

How the math works for any vial (concentration, U-100 units, mg and mcg) is explained step by step on the main peptide reconstitution calculator page. Read the full What is Retatrutide? guide for mechanism, trials and conditions researched.

What published studies used

Research record, not a recommendation or protocol

These are published human trials of Retatrutide from the PeptideWhiz study library. The last column quotes each study’s PubMed abstract word for word, so it shows what that study reported giving its participants under medical supervision. It is not advice, and the calculator never fills these numbers in on its own: you can copy one only by tapping its button and confirming.

Study	Year	Journal	As reported in the abstract	PubMed
Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial.	2026	Lancet (London, England)	“Participants were randomly assigned (1:1:1:1), using an interactive web-response system, to receive once-weekly subcutaneous injections (self-administered) of placebo or retatrutide 4 mg, 9 mg, or 12 mg.”	PMID 42810372
Retatrutide-Associated Improvements in Cardiovascular Risk Biomarkers in Adults With Obesity With or Without Type 2 Diabetes.	2026	Diabetes, obesity & metabolism	“In Study 1, adults with obesity/overweight and T2D received once-weekly retatrutide (0.5/4/8/12 mg), dulaglutide (1.5 mg) or placebo for 36 weeks; in Study 2, adults with clinical obesity without T2D received retatrutide (1/4/8/12 mg) or placebo for 48 weeks.”	PMID 42608321
Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial.	2026	Lancet (London, England)	“Participants were randomly assigned (1:1:1:1) to receive retatrutide (4 mg, 9 mg, or 12 mg) or placebo by once-weekly subcutaneous injection.”	PMID 42250575
Effects of retatrutide on body composition in people with type 2 diabetes: a substudy of a phase 2, double-blind, parallel-group, placebo-controlled, randomised trial.	2025	The lancet. Diabetes & endocrinology	“Eligible participants were randomly assigned in a 2:2:2:1:1:1:1:2 ratio to once-weekly subcutaneous placebo, dulaglutide 1·5 mg, or retatrutide 0·5 mg, 4 mg (2 mg initial dose), 4 mg (4 mg initial dose), 8 mg (2 mg initial dose), 8 mg (4 mg initial dose), or 12 mg.”	PMID 40609566
Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA.	2023	Lancet (London, England)	“Participants were randomly assigned (2:2:2:1:1:1:1:2) using an interactive web-response system, with stratification for baseline HbA1c and BMI, to receive once-weekly injections of placebo, 1·5 mg dulaglutide, or retatrutide maintenance doses of 0·5 mg, 4 mg (starting dose 2 mg), 4 mg (no escalation), 8 mg (starting dose 2 mg), 8 mg (starting dose 4 mg), or 12 mg (starting dose 2 mg).”	PMID 37385280

Disclaimer: this table is an educational research record. It does not recommend, suggest or endorse any amount, schedule or use, and it is not medical advice. Decisions about any medicine belong with a licensed clinician.

Retatrutide calculator FAQ

What is Retatrutide?

Retatrutide is a investigational GIP, GLP-1 and glucagon receptor agonist. Retatrutide (LY3437943) is an investigational single peptide that acts on three receptors: GIP, GLP-1 and glucagon.

Is Retatrutide approved?

Retatrutide is not approved by the FDA or any other regulator. It is in late-stage clinical trials, and the human data so far come from clinical trials such as those listed below.

Does this page suggest a Retatrutide dose?

No. The calculator dose field starts empty and PeptideWhiz never suggests, recommends or calculates an amount for anyone. The study table is a research record of what published trials reported, not a recommendation or protocol.

Where do the study numbers on this page come from?

Each row quotes the abstract of a published human trial (5 trials, 2023 to 2026) word for word, as indexed in PubMed, with a link to the PubMed record. Nothing is rounded, combined or converted.

How does the calculator work with a Retatrutide vial?

Pick Retatrutide in step 1 if you want it on your result card, then enter the vial amount printed on your own label and the water volume actually added. The tool divides one by the other for concentration and shows the matching U-100 syringe units for an amount you type. Pens and pre-filled syringes are already in liquid form and are not reconstituted.

Sources

Study rows: PubMed records linked in the table (abstracts checked against PubMed on October 31, 2026). Unit math: see the sources on the main calculator.

Reviewed by the PeptideWhiz team on October 31, 2026. For research and education only.