Two vials at the same sticker price can cost wildly different amounts per month once you account for dose — which is why price-per-mg, not price-per-vial, is the only number that matters.

Because each GLP-1 compound is dosed differently and titrated over months, comparing cost requires a little math. This guide shows you how to calculate true monthly cost, how research-grade pricing compares to pharmacy list prices, and how to bring the cost down.

This 2026 guide focuses on the true cost per month for the three leading GLP-1 weight-loss research compounds — Semaglutide, Tirzepatide, and Retatrutide. For the full picture, start at the GLP-1 weight loss hub and the GLP-1 research guide.

Why Sticker Price Misleads You

A cheap-looking vial can be expensive per month if its mg-per-dollar is poor or the dose is high.

Each compound's maintenance dose is different, so monthly consumption differs even at the same price-per-mg.

Prices move constantly and vary by vendor, so a one-time comparison goes stale fast.

How to Calculate True Monthly Cost

Sticker price per vial tells you almost nothing. The number that matters is cost per month at your maintenance dose. Here's the formula:

1. Find price-per-mg: vial price ÷ total mg in the vial.
2. Find monthly mg: weekly maintenance dose (mg) × 4.3 weeks.
3. Multiply: monthly mg × price-per-mg = your real monthly cost.

Buying larger-mg vials almost always lowers price-per-mg, which lowers your monthly cost — provided you can use the product before it expires.

Why Monthly Cost Differs by Compound

Each compound's maintenance dose is different, so even at the same price-per-mg the monthly spend varies. Use the live prices on each product page to run the numbers.

Semaglutide

Typical maintenance dose: 2.4mg once weekly. The 4-week-per-step titration ladder used in the STEP program exists to let gastrointestinal side effects settle before each dose increase. Researchers who escalate faster consistently report more nausea. If a given step is not tolerated, the literature supports holding at the current dose for an additional 4 weeks rather than pushing higher.

Run your cost calculation against the current price-per-mg here: Semaglutide price comparison.

Tirzepatide

Typical maintenance dose: 15mg once weekly. Tirzepatide uses a longer ladder with more steps because its larger maintenance doses require gradual GI acclimation. The 2.5mg starting dose is explicitly a tolerance-building dose, not a therapeutic target. Many research protocols find a plateau of acceptable effect at 10mg, so escalating all the way to 15mg is not always necessary.

Run your cost calculation against the current price-per-mg here: Tirzepatide price comparison.

Retatrutide

Typical maintenance dose: 12mg once weekly. All retatrutide dosing is investigational and drawn from the Phase 2 trial design. Because it is the newest and least-studied of the three, conservative titration is especially important. There is no established 'standard' maintenance dose the way there is for semaglutide and tirzepatide.

Run your cost calculation against the current price-per-mg here: Retatrutide price comparison.

A Worked Example

Suppose a 10mg vial of a compound costs a given price. Its price-per-mg is that price ÷ 10. If your maintenance dose is 5mg/week, you use about 5 × 4.3 ≈ 21.5mg per month — just over two 10mg vials. Your monthly cost is roughly 21.5 × price-per-mg. Swap in the live numbers from the product pages to get your actual figure. The same method works for any compound and any dose.

Research-Grade vs Pharmacy Pricing

Pharmacy list prices for the branded products (Ozempic, Wegovy, Mounjaro, Zepbound) are commonly cited in the four-figures-per-month range without insurance. Research-grade compounds typically cost a fraction of that. But that gap reflects a real difference: branded products are regulated, formulated, and approved for human use, while research-grade compounds are unregulated and sold for research only. The price difference is not a simple markup — it's a quality-assurance and regulatory difference.

How to Lower Your Cost (Without Lowering Quality)

• Compare price-per-mg across vendors with DiscountChems rather than buying from the first source you find.
• Apply discount codes — partner vendors frequently offer savings of up to 35% off; check each product page.
• Buy larger-mg vials for a better per-mg rate, if you'll use them before expiry.
• Don't over-escalate. Staying at the dose that achieves your goal — rather than pushing to the top of the ladder — directly reduces monthly mg and cost.
• Never trade a verified COA for a few dollars. Underdosed product is the most expensive purchase there is.

Research-Grade vs Pharmaceutical Products

Research-grade Semaglutide, Tirzepatide, and Retatrutide contain only the active peptide and are sold strictly for laboratory research. They are not equivalent to, or interchangeable with, FDA-approved products such as Ozempic, Wegovy, Mounjaro, or Zepbound, which include pharmaceutical-grade formulation, delivery devices, and regulatory approval for human use. Nothing in this article is medical advice.

Where to Source Research-Grade Compounds

Quality and purity are paramount when sourcing research chemicals. The factors that matter most:

• Documentation: A trustworthy vendor publishes third-party CoAs (HPLC or mass spec) for each batch, showing purity at or above 98%.
• Consistency: Established sellers with steady quality, clear test results, and quick support are worth more than the cheapest unknown source.
• Smart comparison: Run the numbers on price-per-mg with DiscountChems to find the best real value across trusted vendors.

Compare prices for compounds discussed in this article:

• Semaglutide — compare prices across vendors
• Tirzepatide — compare prices across vendors
• Retatrutide — compare prices across vendors

Exclusive vendor codes can cut up to 35% off — they're shown on the individual product pages.

Frequently Asked Questions

How do I calculate my real monthly cost?

Take your weekly maintenance dose in mg, multiply by ~4.3 for weeks per month, then multiply by the price-per-mg of the vial size you buy. Price-per-mg is the vial price divided by its total mg. Buying larger-mg vials usually lowers price-per-mg, which lowers monthly cost.

Is research-grade cheaper than getting a prescription?

Pharmacy list prices for the branded products are commonly cited in the four-figures-per-month range without insurance. Research-grade compounds are typically a fraction of that, but they are unregulated, sold for research only, and not equivalent to approved products. The cost gap reflects a regulatory and quality-assurance gap, not just a markup.

Which compound is cheapest per month?

It depends on the current price-per-mg of each and your maintenance dose. Semaglutide's low maintenance dose (2.4mg/week) can offset a higher price-per-mg, while tirzepatide and retatrutide use larger doses. Always run the calculation on live prices from each product page rather than assuming.

How do I lower the cost?

Compare price-per-mg across vendors with DiscountChems, apply available discount codes (often up to 35% off), buy larger-mg vials for a better per-mg rate, and avoid escalating past the dose that achieves your goal. Don't chase the lowest price at the expense of a verified COA.

References & Research Citations

1. [1] Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384(11):989-1002.
2. [2] Frías JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). N Engl J Med. 2021;385(6):503-515.
3. [3] Knudsen LB, Lau J. The Discovery and Development of Liraglutide and Semaglutide. Front Endocrinol. 2019;10:155.
4. [4] Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205-216.
5. [5] Jastreboff AM, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526.

Note: This list is not exhaustive. Researchers should consult primary sources and their institutional review boards for the most current data.

Related Resources on DiscountChems

• GLP-1 weight loss peptides hub — compare every option
• GLP-1 research guide: Semaglutide vs Tirzepatide vs Retatrutide
• Semaglutide vs Tirzepatide comparison
• Tirzepatide vs Retatrutide comparison
• Semaglutide price comparison
• Tirzepatide price comparison
• Retatrutide price comparison
• Semaglutide dosage guide
• Tirzepatide dosage guide
• Retatrutide dosage guide

Conclusion

Real GLP-1 cost is a function of dose and price-per-mg, not the number on the vial. Run the simple monthly-cost calculation on live prices, factor in discount codes, and never trade away verified quality for a few dollars. Compare current prices on each product page and start at the GLP-1 hub.

When you're ready to source, DiscountChems shows live price comparisons across lab-tested vendors for everything mentioned above.

Want a second opinion before you start? Join the free DadBod2Fit community on Skool — it's free, active, and full of researchers sharing what's working (and what isn't).