Retatrutide Pricing: Comparing Listings on Purity and Value

Retatrutide pricing has two numbers in it: the vial price a listing leads with, and the cost per milligram sitting underneath it. In one research-supply catalog priced 10 September 2026, a 10 mg vial at $100 works out to $10.00/mg and a 20 mg vial at $195 to $9.75/mg, a 2.5% difference. Adjust each for the purity a certificate of analysis reports and that gap narrows or flips: the 20 mg vial has to test at roughly 96.5% or better to stay cheaper than a 10 mg vial testing at 99%. Value is the purity-adjusted figure, not the sticker.

What does a retatrutide listing cost per milligram?

Divide the listed vial price by the milligrams in the vial. That single step normalizes every listing to one unit and removes the packaging from the comparison.

Vial size (mg)	Listed price (USD)	Arithmetic	Cost per mg (USD)
10	100	100 ÷ 10	10.00
20	195	195 ÷ 20	9.75

Cost per milligram at two vial sizes. Prices from a research-supply catalog pulled 10 September 2026; the cost-per-mg column is the listed price divided by the vial’s milligram content.

Buying 20 mg as two 10 mg vials costs 2 × $100 = $200 against $195 for the single 20 mg vial, so the larger size saves $5 on the same quantity of material. That is the entire size discount at these two prices, and it is small enough that a second variable can erase it.

What does reported purity do to the per-mg price?

A vial labeled 10 mg at 98% purity contains 9.8 mg of the target peptide and 0.2 mg of something else. Costing the vial against its labeled mass overstates what you are actually buying, so the honest denominator is labeled mass multiplied by the purity fraction:

effective cost per mg = vial price ÷ (vial mg × purity fraction)

Reported purity (%)	10 mg vial at $100 (USD/mg)	20 mg vial at $195 (USD/mg)
99.0	10.10	9.85
98.0	10.20	9.95
95.0	10.53	10.26

Purity-adjusted cost per milligram at the two catalog prices above (as of September 2026). The purity values are illustrative inputs, not measured results from any specific listing. Each cell is price ÷ (mg × purity): $100 ÷ (10 × 0.99) = $10.10, $100 ÷ (10 × 0.98) = $10.20, $100 ÷ (10 × 0.95) = $10.53, $195 ÷ (20 × 0.99) = $9.85, $195 ÷ (20 × 0.98) = $9.95, $195 ÷ (20 × 0.95) = $10.26.

Read the table across rather than down and the point lands: a 20 mg vial documented at 95% costs $10.26/mg, which is worse than a 10 mg vial documented at 98% at $10.20/mg. A three-point purity gap outweighs a 2.5% size discount.

The breakeven is computable. Setting the 20 mg vial equal to a 10 mg vial at 99% purity ($10.101/mg): $195 ÷ (20 × p) = $10.101, so 20p = 195 ÷ 10.101 = 19.305, and p = 0.9653. The 20 mg vial needs a documented assay of about 96.5% before its lower headline per-mg price survives contact with the purity number. Listings that give you purity reported as a range rather than a single figure force you to run this twice, once at each end of the range, and compare the pessimistic case.

Why is there no manufacturer list price for retatrutide at all?

Retatrutide is not an approved product, so no manufacturer price schedule exists to anchor against. The TRIUMPH program is still running four Phase 3, multicenter, randomized, double-blind studies of once-weekly subcutaneous retatrutide versus placebo in over 5800 participants, with percent change in body weight as the weight-management primary endpoint, according to the 2026 TRIUMPH trial design paper in Diabetes, Obesity and Metabolism. Registrational trials of that size do not produce a public price.

Before those, the phase 2 obesity trial enrolled 338 adults into 1 mg, 4 mg, 8 mg and 12 mg once-weekly arms for 48 weeks, reporting a least-squares mean weight change at 24 weeks of −7.2% in the 1 mg group and −17.5% in the 12 mg group against −1.6% on placebo, per the 2023 NEJM phase 2 retatrutide report. Every price you can look up today is therefore a research-supply listing set by the supplier, which is why the spread between listings is wide and why retatrutide pricing has no reference point except other listings. These materials are sold for laboratory research use only.

Does the lowest price per mg always win?

No, and the failure mode is usually the denominator rather than the price. A vial is 10 mg for costing purposes only if the fill matches the label, which puts vial fill volume claims in the same check as the arithmetic. An undocumented 10 mg vial that actually contains 8 mg costs $12.50/mg, not $10.00, and no purity percentage on the page corrects for that.

The relationship does not run in reverse either. A higher number on the page certifies nothing about the assay behind it, and treating price as a purity proxy substitutes a marketing decision for a measurement. The position worth holding is narrow: compare per-milligram prices only between listings that publish a lot-matched certificate of analysis, and treat an unpublished COA as an unknown denominator rather than a discount.

That cuts both directions. Listings far under market average are the clearest case, because a per-milligram figure well below the rest of the market is either a real cost advantage the supplier can document or a denominator problem the supplier has not disclosed, and the COA is what separates the two.

How much material does a listing comparison actually cover?

Enough that a small per-milligram gap compounds. The phase 2 obesity trial’s 12 mg arm ran 48 weeks, and at a flat 12 mg per week that arithmetic is 12 × 48 = 576 mg, though participants in that arm titrated up from a 2 mg initial dose, so real exposure over the 48 weeks was lower than the flat figure (NEJM 2023, PMID 37366315).

Cost 576 mg at the two catalog rates: 576 × $9.75 = $5,616, against 576 × $10.00 = $5,760. The difference is $144 on a quantity that is only 2.5% apart per milligram. Rounded up to whole vials, 576 ÷ 20 = 28.8 becomes 29 twenty-milligram vials, while 576 ÷ 10 = 57.6 becomes 58 ten-milligram vials.