David DeMesquita's Retatrutide Injection Guide: What He Shows and What You Should Know

David DeMesquita's Retatrutide Injection Guide: What He Shows and What You Should Know

In 2026, fitness content creator David DeMesquita posted a practical video titled "How to Measure and Inject Retatrutide (GLP-3 Triple Agonist)" walking through the full process of reconstituting grey market retatrutide, measuring doses with insulin syringes, and performing subcutaneous injection. The video has become a popular reference in peptide communities.

This page breaks down what DeMesquita demonstrates, where his technique aligns with pharmaceutical best practice, and where critical safety context is missing. DeMesquita is not a pharmacist or physician, and the product he demonstrates is not FDA-approved retatrutide.

The "GLP-3" Labeling Problem

DeMesquita opens by explaining why the product is labeled "GLP-3" rather than retatrutide:

"Most bottles will be labeled as GLP-3 because it is technically not allowed to be sold right now. It's not FDA approved and Eli Lilly owns a patent so they don't want anyone to sell it."

— David DeMesquita

This is largely accurate. Grey market vendors label retatrutide as "GLP-3 triple agonist" or similar to avoid trademark and regulatory issues. Eli Lilly holds the patent on retatrutide and the compound is not approved for any use. Products sold as "GLP-3" are classified as research chemicals — they are not pharmaceutical-grade, not subject to FDA quality controls, and may contain impurities including lipopolysaccharide (LPS).

The term "GLP-3" itself is informal slang, not a scientific classification. There is no third GLP hormone — the name refers to retatrutide being a triple agonist of GLP-1, GIP, and glucagon receptors. For more on the naming, see What Is Retatrutide.

Reconstitution: His Method

DeMesquita demonstrates reconstituting a 10mg vial of lyophilized (freeze-dried) retatrutide with 1ml of bacteriostatic water. His technique:

  1. Bacteriostatic water — he correctly emphasizes not using tap water ("please do not shoot sink water into this thing") and recommends bacteriostatic water containing benzyl alcohol as a preservative
  2. Volume calculation — 10mg vial + 1ml water = each 10 IU mark on the insulin syringe equals 1mg
  3. For a 20mg vial — he advises doubling the water to 2ml to keep the same concentration
  4. Mixing — he rolls the vial gently rather than shaking, which is correct technique for peptides (shaking can denature the protein)
  5. Storage — refrigerate after reconstitution
StepWhat He DoesBest Practice
SolventBacteriostatic waterCorrect — BAC water with benzyl alcohol is standard for reconstituted peptides
Volume1ml per 10mg vialReasonable — keeps math simple for dosing
MixingGentle rollingCorrect — shaking can damage peptide structure
StorageRefrigerate after reconstitutionCorrect — reconstituted peptides degrade at room temperature
Air pressure equalizationPushes air into vial if solution is hard to drawStandard technique for sealed vials

His reconstitution technique is broadly sound from a practical standpoint. The fundamental problem is not his technique — it is that the starting material is unverified grey market product with no certificate of analysis from an independent lab.

For more on reconstitution, see Retatrutide Reconstitution.

His Dosing: Far Below Clinical Trials

DeMesquita reveals he uses a notably low dose compared to clinical trials:

"I actually do a split dose. I only do 0.5 milligrams per week. I do a very small amount... I actually got a decent appetite reduction even at low dosages of 1 milligram per week."

— David DeMesquita

He describes splitting 1mg into two 0.5mg injections per week, and notes that he uses retatrutide primarily for blood sugar management rather than weight loss, citing episodes related to Graves' disease.

Dosing ContextDoseNotes
DeMesquita's dose0.5–1 mg/weekRoughly 1/12th to 1/4th of Phase 3 doses
Phase 3 lowest dose2 mg/week (starting)Titration starting point in TRIUMPH program
Phase 3 target doses9–12 mg/weekDoses that produced 26–29% weight loss
Phase 2 lowest effective dose1 mg/weekProduced only -3.19% weight loss at 48 weeks

At 0.5–1mg per week, DeMesquita is using retatrutide at a fraction of the doses studied in clinical trials. In the Phase 2 trial, the 1mg dose produced only 3.19% weight loss over 48 weeks — barely more than placebo (2.08%). His report of appetite reduction at this dose is anecdotal and could reflect placebo effect, individual sensitivity, or properties of the specific grey market product he is using.

The concept of using lower doses is discussed more broadly in Microdosing Retatrutide. For clinical dosing data, see Retatrutide Dosage.

Injection Technique

DeMesquita demonstrates subcutaneous injection around the belly button, using a pinch-and-inject technique:

"I go around the belly button. The left side for me feels way better than my right side... I take the skin and I pull it from my body and then I pop it in."

— David DeMesquita

He also shares tips for avoiding post-injection welts — rolling the skin after injection to disperse the fluid, and applying heat to the area.

His claim that subcutaneous injection "slightly elongates the half-life" compared to intramuscular is a common belief in peptide communities. For GLP-1 receptor agonists generally, subcutaneous administration is the standard clinical route — both semaglutide (Ozempic/Wegovy) and tirzepatide (Mounjaro/Zepbound) are administered subcutaneously. Retatrutide was given subcutaneously in all clinical trials.

For more on injection technique, see How to Inject Retatrutide.

Combining Multiple Peptides in One Syringe

DeMesquita mentions combining multiple compounds into a single injection:

"What's in here right now is going to be some retatrutide, HCG, FSH, BPC-157, and TB-500."

— David DeMesquita

He acknowledges that water-based solutions can technically be combined but advises keeping them in separate vials for accurate measurement. The practice of combining multiple peptides in a single syringe is common in the self-administration community but raises several concerns:

  • No stability data exists on retatrutide combined with HCG, FSH, BPC-157, or TB-500 in solution
  • Peptide interactions in solution can cause aggregation, degradation, or reduced potency
  • Dosing errors become more likely when multiple compounds are measured sequentially into one syringe
  • Adverse event attribution becomes impossible when multiple compounds are injected simultaneously

Frequently Asked Questions

Who is David DeMesquita?

David DeMesquita is a fitness content creator who produces videos on peptides, performance-enhancing compounds, and body composition. He is not a pharmacist, physician, or medical researcher. His retatrutide video demonstrates practical reconstitution and injection technique for grey market product.

Is his reconstitution technique correct?

His basic technique — using bacteriostatic water, gentle rolling to mix, and refrigerating after reconstitution — follows standard practice for reconstituting lyophilized peptides. The math for concentration (10mg in 1ml = 1mg per 10 IU) is correct. The fundamental issue is not his technique but the unverified quality of grey market "GLP-3" products.

Is 0.5mg retatrutide per week effective?

There is no published clinical data supporting retatrutide at 0.5mg per week. The lowest dose tested in Phase 2 trials was 1mg per week, which produced only 3.19% weight loss over 48 weeks — barely above placebo. DeMesquita's report of appetite reduction at this dose is anecdotal. Individual responses vary, and the potency of grey market products is unverified.

Is it safe to combine retatrutide with other peptides in one syringe?

No published safety or stability data exists on combining retatrutide with HCG, FSH, BPC-157, TB-500, or any other compound in the same syringe. Mixing peptides can cause degradation, aggregation, and unpredictable interactions. While DeMesquita and others in the peptide community routinely combine compounds, this practice has no clinical evidence supporting its safety.

Should I follow this video to inject retatrutide?

This video demonstrates grey market peptide preparation, not pharmaceutical-grade drug administration. Retatrutide is not FDA-approved and cannot be legally obtained as a medication outside of clinical trials. Grey market products labeled "GLP-3" have no quality assurance, may contain impurities, and carry risks of contamination. If you are interested in retatrutide, the safest option is enrolling in a clinical trial.

Sources

  • DeMesquita, D. (2026). "How to Measure and Inject Retatrutide (GLP-3 Triple Agonist)." YouTube. Watch on YouTube
  • Jastreboff, A.M., et al. (2023). Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine. DOI: 10.1056/NEJMoa2301972
  • Eli Lilly and Company. (2025). Lilly's retatrutide achieved significant weight loss and pain relief in adults with obesity and knee osteoarthritis. Press release

Medical Disclaimer

The content on glp3.wiki is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Retatrutide is an investigational drug that has not been approved by the U.S. Food and Drug Administration (FDA) or any other regulatory agency.

David DeMesquita's video is not medical instruction. He is not a pharmacist or physician. The product he demonstrates is unregulated grey market material, not pharmaceutical-grade retatrutide. His technique, while practical, does not substitute for proper medical guidance.

Do not use this information to make decisions about your health without consulting a qualified healthcare provider. Do not purchase or self-administer grey market peptides based on YouTube videos or any information on this site.

This site is not affiliated with David DeMesquita, Eli Lilly and Company, or any pharmaceutical manufacturer.

Sources