What is GLP-3 retatrutide?

"GLP-3" is a community nickname for retatrutide (LY3437943), an investigational once-weekly drug from Eli Lilly that activates GIP, GLP-1 and glucagon receptors. It is not an official drug class. As of Oct 19, 2026 it is not FDA approved; Lilly plans a US submission in the first quarter of 2027.

Is retatrutide FDA approved?

No. It is investigational and legally available only to participants in Lilly clinical trials. Products sold online as research retatrutide are unapproved, and the FDA has sent warning letters to sellers.

How many units is 2.5 mg of tirzepatide?

It depends on concentration: units = mg ÷ (mg/mL) × 100. At 10 mg/mL it is 25 units; at 5 mg/mL (the strength of Zepbound single-dose products, 2.5 mg per 0.5 mL) it is 50 units. Follow your prescription label.

What is a GLP-1 dose plotter?

A tool that draws the modeled amount of a weekly medicine over time from its half-life, so you can see how doses overlap and build after each step. GLP Ladder's plotter runs in your browser with a one-compartment model and shows a data table alongside the chart.

Does GLP Ladder give dosing advice?

No. The calculators do arithmetic on numbers you enter and lay out schedules exactly as published in trials or FDA labels. For an approved medicine, your prescriber sets your dose; retatrutide is not available outside clinical trials.

GLP-1 and retatrutide math, charted and sourced

Calculators and charts for retatrutide, tirzepatide and semaglutide. Published ladders only, every number dated and sourced, no account needed.

Open the plotter All calculators

Modeled estimates for research and education; not dosing advice. Retatrutide is investigational.

Retatrutide Phase 3 12 mg arm as published (dataset), modeled with t½ = 6 days.

Calculators

Start from the job, then pick the compound. Each calculator shows its formula and a worked example.

Your medication

All RetatrutideTirzepatideSemaglutide

See levels over time

Model how weekly doses overlap and build, with published ladders preloaded.

Dose-level plotter

weekly mg + t½ gives mg-eq curve

One-compartment Bateman model with published ladder presets, weekly peaks and troughs, and CSV export.

Convert mg, mL and units

Vial arithmetic for U-100 syringes, from any vial strength and water volume.

mg to units

mg ÷ mg/mL × 100 gives units

A dose in mg as U-100 units, with the concentration, mL and doses per vial.
Reconstitution

vial mg ÷ water mL gives mg/mL

Concentration from vial mg and water mL, units on a U-100 syringe, and the water for a target mark.
Pen-to-vial converter
pen mg + vial mg/mL gives units

Labeled pen doses for four brands, as units from any vial strength.

Plan a schedule

Week-by-week dates for published trial and label ladders.

Titration schedule

ladder + start date gives dated weeks

Published trial and label ladders as a dated, week-by-week table.

Supply and storage

Cost from your own prices, and discard-by dates from label in-use periods.

Cost

mg/week × weeks + price gives vials, cost

Total mg for a schedule or published ladder, whole and fractional vials, and cost per mg from your price.
Storage dates

start date + days gives discard-by

Discard-by date and days left from label in-use periods, or from a period you enter.

Compounds

Status and model half-life as of Oct 19, 2026
Compound	Half-life	Status	Receptors
Retatrutide	6 days	Investigational. Not FDA approved; available legally only in Lilly clinical trials.	GIP, GLP-1 and glucagon receptor agonist (a "triple agonist")
Tirzepatide	5 days	FDA approved as Mounjaro (type 2 diabetes) and Zepbound (weight management, obstructive sleep apnea).	GIP and GLP-1 receptor agonist (a "dual agonist")
Semaglutide	7 days	FDA approved as Ozempic (type 2 diabetes) and Wegovy (weight management, cardiovascular risk reduction).	GLP-1 receptor agonist

What changed

Dated trial, label and regulatory events reflected on this site. Checked Oct 19, 2026.

Latest events (newest first, each with its source)

Sep 29, 2026

TRIUMPH-1 in NEJM; TRIUMPH-2 in The Lancet

Trial readout. Source: N Engl J Med.
Aug 28, 2026

Zepbound prescribing information revised

Label update. Source: DailyMed.
Aug 24, 2026

FDA warning letter to a "GLP-3R" research-peptide seller

Regulatory. Source: FDA.
Aug 12, 2026

Lilly acts against online retatrutide sellers

Regulatory. Source: Eli Lilly.
Jul 23, 2026

TRIUMPH-2 and -3 topline; US submission planned for Q1 2027

Trial readout. Source: Eli Lilly.
May 21, 2026

TRIUMPH-1 topline: 12 mg −28.3% at 80 weeks (efficacy estimand)

Trial readout. Source: Eli Lilly.
Mar 19, 2026

Wegovy HD (7.2 mg) approved

FDA approval. Source: FDA.

Charts and guides

Table-first reference pages, grouped by compound. Start with the dosage chart, then units, reconstitution and half-life.

Frequently asked questions

What is GLP-3 retatrutide?: "GLP-3" is a community nickname for retatrutide (LY3437943), an investigational once-weekly drug from Eli Lilly that activates GIP, GLP-1 and glucagon receptors. It is not an official drug class. As of Oct 19, 2026 it is not FDA approved; Lilly plans a US submission in the first quarter of 2027.
Is retatrutide FDA approved?: No. It is investigational and legally available only to participants in Lilly clinical trials. Products sold online as research retatrutide are unapproved, and the FDA has sent warning letters to sellers.
How many units is 2.5 mg of tirzepatide?: It depends on concentration: units = mg ÷ (mg/mL) × 100. At 10 mg/mL it is 25 units; at 5 mg/mL (the strength of Zepbound single-dose products, 2.5 mg per 0.5 mL) it is 50 units. Follow your prescription label.
What is a GLP-1 dose plotter?: A tool that draws the modeled amount of a weekly medicine over time from its half-life, so you can see how doses overlap and build after each step. GLP Ladder's plotter runs in your browser with a one-compartment model and shows a data table alongside the chart.
Does GLP Ladder give dosing advice?: No. The calculators do arithmetic on numbers you enter and lay out schedules exactly as published in trials or FDA labels. For an approved medicine, your prescriber sets your dose; retatrutide is not available outside clinical trials.

Sources for the dates above

Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity. N Engl J Med (abstract via PubMed PMID 42814954; doi:10.1056/NEJMoa2604169), Sep 29, 2026. Accessed Oct 19, 2026.
ZEPBOUND (tirzepatide) injection, for subcutaneous use - Full Prescribing Information, Medication Guide and Instructions for Use (DailyMed SPL set ID 487cd7e7-434c-4925-99fa-aa80b1cc776b, version 40). U.S. National Library of Medicine (DailyMed) / Eli Lilly and Company, Aug 28, 2026. Accessed Oct 19, 2026.
Warning Letter: Peak Performance Peptides, MARCS-CMS 735127. U.S. Food and Drug Administration, Aug 24, 2026. Accessed Oct 19, 2026.
Lilly calls on online platforms, payment companies and regulators to shut down the illegal retatrutide black market. Eli Lilly and Company (via PR Newswire), Aug 12, 2026. Accessed Oct 19, 2026.
Lilly's triple agonist, retatrutide, successful in two additional Phase 3 obesity trials, delivering significant improvements in weight and A1C. Eli Lilly and Company (via PR Newswire), Jul 23, 2026. Accessed Oct 19, 2026.
Lilly's triple agonist, retatrutide, delivered powerful weight loss in pivotal Phase 3 obesity trial. Eli Lilly and Company (via PR Newswire; also investor.lilly.com), May 21, 2026. Accessed Oct 19, 2026.
FDA Approves Fourth Product Under National Priority Voucher Program, Higher Dose Semaglutide. U.S. Food and Drug Administration, Mar 19, 2026. Accessed Oct 19, 2026.