Best Retatrutide Vendors for 2026: Where Researchers Buy After the Peptide Sciences Shutdown

On March 6, 2026, Peptide Sciences voluntarily shut down. They were one of the largest retatrutide sources in the market, running roughly $7.45M in monthly sales. Finnrick had already graded them an E across 37 samples, with at least one batch confirmed to contain the wrong peptide entirely.

Price, not quality, kept buyers there. If you are reading this, you probably need a new vendor.

We ranked six of them against four pillars: COA completeness, mass-spec identity verification, TFA counterion documentation, and named third-party lab accreditation. The mass-spec pillar is the one most buyers ignore.

Retatrutide free base weighs 4,731.33 g/mol. TFA salt weighs 4,845.35 g/mol. Exendin-4, the most common substitute in this category, weighs 4,186.58 g/mol. HPLC cannot tell those molecules apart; mass spectrometry can.

A vendor that does not report an observed mass on the COA is a vendor that cannot prove what is in the vial.

Finnrick's 2,489-sample dataset across 164 vendors is the best independent data point we have for this market. We reference it throughout, but we do not use it as our methodology. Finnrick tests blind. We grade what a buyer can verify before paying. Those are different measurements and they produce a different ranking.

The window for this article is narrow. Eli Lilly's NDA for retatrutide is projected for Q4 2026, with FDA approval expected late 2027 or Q1 2028. The TRIUMPH-4 Phase 3 readout showed 28.7% weight loss at 12mg over 68 weeks, the highest ever for a Phase 3 obesity trial.

In February 2026 the FDA restored 14 peptides to Category 1 status for compounding pharmacy access. Retatrutide was not on that list. Research-chemical access is the only legal path right now, and it will contract once approval lands.

Below: how we graded the six, why two of Finnrick's top-three picks did not make our top three, a full per-mg pricing table, and the FAQ most vendors will not answer in writing. Our four-pillar methodology comes first.

How We Graded Retatrutide Vendors: The Mass Spec Problem Nobody Is Talking About

In one independent analysis of 1,866 samples from 134 vendors, 23% of retatrutide-labeled vials contained exendin-4 analogs. Reported HPLC purity on many of those was above 98%. The vials were clean. They were just clean of the wrong molecule.

Finnrick's rating distribution across 164 vendors is the other piece of context worth carrying into a buying decision: 29 A-grades, 25 B, 46 C, 20 D, 42 E, 4 outright F-graded fraud operations, and 6 unrateable X. Nantong Guangyuan was the most visible F, caught fabricating COAs at scale with labels that had never been on a mass spectrometer. Our four-pillar grading system is the filter designed to catch those vendors before a buyer hands over a credit card.

• COA completeness. Batch-specific, dated, method disclosed, not a stock image reused across SKUs. A COA that could apply to any batch applies to no batch.
• Mass-spec identity. Observed mass is required. Retatrutide free base = 4,731.33 g/mol. TFA salt = 4,845.35 g/mol. Exendin-4 = 4,186.58 g/mol. If the COA does not publish an observed mass, you cannot verify identity. HPLC purity is a purity number, not an identity number.
• TFA documentation. Solid-phase peptide synthesis leaves trifluoroacetic acid counterions bound to the peptide. Residual TFA is not harmless at scale. A vendor publishing a residual TFA percentage is telling you they know what is in the vial beyond the active molecule. A vendor silent on TFA is telling you the opposite.
• Lab accreditation. Named third-party lab. Ideally ISO 17025 or CLIA. “Independently tested” with no lab name attached is marketing copy, not accreditation.

There is a fifth signal that does not fit into a pillar but matters: quantity deviation. Finnrick's dataset shows ±45% deviation at the 95th percentile. A vial labeled 10mg can contain anywhere from 5.5mg to 14.5mg of actual peptide. SeekPeptides' own sourced analysis found vials labeled 10mg containing only 2.3mg to 6.8mg of actual peptide. That is a 58% underdose at the worst end. Only one vendor in our top six publishes the actual net weight of each vial on the COA, and that is why they rank where they do.

One honest caveat. Paradigm Peptide holds the highest Finnrick average for retatrutide, 9.6 across 6 blind tests, A rating. They also publish zero COAs, name no labs, and show no mass-spec data on product pages.

Finnrick tests what is in the vial. We grade what a buyer can see before they buy. Those are different jobs, which is why our ranking puts Paradigm sixth while Finnrick ranks them first. Neither of us is wrong; we are answering different questions.

With that grading system in mind, here are the six vendors worth considering in April 2026.

1. Peptide Partners: The Best Documentation Stack in the Market

If you want one vendor to default to, this is it.

Finnrick graded them A across 14 tests. Average score 8.9, range 7.0 to 10.0. The range matters more than the average. A tight range across 14 tests means nobody is cherry-picking batches to submit.

The company is Pirsek Technologies LLC, based in Florida. Vials ship in a single 24mg format, which is unusual enough to flag. Most research vendors default to round-number sizes (10mg, 20mg, 30mg). The 24mg choice aligns with the 12mg-titrated protocol dosing that TRIUMPH Phase 3 used (two doses per vial with modest overfill headroom). It is a format decision that reads as protocol-aware rather than retail-friendly. Free shipping kicks in over $400.

COA scorecard.

• Completeness: Four-category verification on every COA (HPLC, USP<85> endotoxin, ICP-MS heavy metals, sterility). Batch-specific and dated.
• Mass-spec identity: Yes. Observed mass reported on every COA.
• TFA documentation: Published as a residual number.
• Labs: TrustPointe Analytics, BioRegen, Chromate, and Kovera Labs. Four separate labs rotating across batches. Nobody else in this category runs a four-lab stack.

The Finnrick range of 7.0 to 10.0 across 14 tests is the tell. Vendors who submit best-case batches to blind testers get narrow high ranges. A wider range that stays above failure thresholds means Finnrick pulled those batches off the shelf from the same pool a buyer would pull from. Batch IDs are matched to vial labels, so the COA a buyer downloads is verifiably the COA for the vial in hand.

One footnote worth naming neutrally. Peptide Partners had a Trustpilot page with 83 reviews at 4.4 stars that was removed. We mention it because a search will surface it and we do not hide things. We have no inside information on why it was removed, and the four-lab COA stack stands on its own.

A smaller caveat worth flagging: retatrutide holds an A, but Finnrick graded their CJC-1295 and tirzepatide C across separate tests. Quality at this vendor is molecule-specific, not a blanket house-level grade.

Weaknesses. Only one vial size. Trustpilot history is gone. Per-mg pricing is not the cheapest in this list. If you are optimizing purely on cost, skip down.

Best for: First-time buyers replacing a Peptide Sciences slot. Researchers who will not negotiate on documentation.

Skip if: You need sizes other than 24mg, or per-mg cost is the only metric that matters.

2. Onyx Biolabs: The Only Vendor Publishing Actual Net Content

A 10mg Onyx vial actually contains 14.02mg. A 40mg contains 41.91mg. They publish the scale readout on the COA. If you have read this far, you know why that matters.

Onyx is based in Charlotte, NC. Sizes run 5mg to 40mg, the widest range on our list. Sale prices currently span $54.99 on the smallest vial to $249.99 on the 40mg, which puts the per-mg floor below every vendor in our top six on the small end. Bulk discount tiers: 5% for 2 to 5 vials, 10% for 6 to 10, 20% for 11 or more. Same-day dispatch on orders placed before 2 PM EST.

COA scorecard.

• Completeness: 16 Kovera Labs batch COAs publicly accessible from product pages. Batch-specific, dated. This is the most transparent batch archive on our list.
• Mass-spec identity: Yes.
• TFA documentation: Yes.
• Labs: Kovera Labs only. Single-lab relationship, which is a weakness compared to Peptide Partners, though the published batch depth compensates.
• Net content documented: 10mg vial actual = 14.02mg. 15mg batch RETA0925 = 19.80mg. 30mg = 28.84mg. 40mg = 41.91mg.

Net-content disclosure is a transparency commitment that works against the vendor commercially. If a single vial underfills by even a milligram, it is now documented on the COA. Vendors who are not sure what their fill process produces do not make that commitment. Onyx publishes because their process is tight enough that they can afford to.

The Finnrick ±45% deviation figure is where this matters. For a researcher titrating retatrutide doses, actual net content is the difference between a clean protocol and one where the dose-response curve is corrupted by unknown underfill. Onyx removes that variable. No other vendor on this list does.

Purity runs 99.9% and above consistently across the 16 published batches. The lowest-purity batch we could find in their archive was RETA0925-15-1 at 99.308%, still above the 99% threshold and notable because Onyx published it at all rather than burying the weaker number. They also documented that same batch as a 19.80mg fill on a 15mg-labeled vial (a 32% overfill, not underfill). Publishing overfill data openly is the posture of a vendor who would rather eat margin than ship light.

Weaknesses. Single-lab relationship. Not in the Finnrick dataset, so we have no blind-test corroboration. No Trustpilot history to reference.

One operational caveat on the single-lab relationship. All 16 public COAs run through Kovera Labs. That concentrates risk if Kovera's methodology drifts or their accreditation status changes. Peptide Partners' four-lab rotation and Orbitrex's three-lab stack both hedge that exposure. Onyx compensates by publishing the raw batch data that would let a buyer detect drift themselves, but the underlying structural risk is real.

The verdict: If the ±45% quantity-deviation problem is what keeps you up at night, this is the buy.

3. Ascension Peptides: Triple-CLIA Labs, Best Value at the 30mg Size

Three CLIA-certified labs. $3/mg with the promo code at 30mg. 4.8 across 72 Trustpilot reviews. If you are price-sensitive but will not give up documentation, this is the one.

Ascension ships US-only. R-10 (10mg) runs $70 to $120 depending on promo stack. R-30 (30mg) runs $180 to $200. Trustpilot sits at 4.8/5 across 72 reviews.

COA scorecard.

• Completeness: Batch-specific, HPLC plus mass spec published on each COA.
• Mass-spec identity: Yes.
• TFA documentation: Confirmed.
• Labs: SafeCert Labs, triple CLIA-certified. CLIA stands for Clinical Laboratory Improvement Amendments, the federal standard for diagnostic laboratories. Research peptide vendors almost never pay for CLIA-grade testing. SafeCert holds three separate CLIA certifications, which is why this pillar rates highest on our list for a single-lab relationship.

Ascension is not in the Finnrick top three for retatrutide. A vendor that publishes complete buyer-visible documentation will score well with our four pillars even if Finnrick has not submitted enough of their batches for blind testing to land a top-three slot.

One protocol-planning note worth carrying into a 30mg-vial purchase. TRIUMPH-4 reported dysesthesia (skin hypersensitivity) in roughly 20.9% of patients at the 12mg dose. Titration protocols that reach 30mg-vial territory over multiple weeks need slow escalation. Ascension's size range (10mg and 30mg) is well-matched to a titrated protocol.

Small friction note on the catalog itself. Ascension codes products as R-10, R-30, T-10 (retatrutide 10mg, retatrutide 30mg, tirzepatide 10mg) rather than labeling them plainly. First-time buyers sometimes land on the wrong SKU. This is a UX quibble rather than a quality signal, but it is the single most common friction point in their Trustpilot feedback.

Price spread at 30mg is worth naming. With the 50% promo code, Ascension lands near $3/mg. Paradigm sits at $9 to $10/mg. Peptide Partners is higher still on a per-mg basis given the 24mg-only format. Ascension is the only vendor on this list where aggressive promo pricing does not come at the cost of documentation.

Weaknesses. US-only, so international researchers are excluded. Narrower size range than Onyx. Promo-dependent pricing means the headline per-mg number is not always available.

Quick comparison.

• vs Peptide Partners: Cheaper per mg. Weaker multi-lab redundancy.
• vs Onyx: Comparable lab accreditation quality. Narrower size range. No net-content disclosure.
• vs Paradigm: Much better documentation at roughly one third the per-mg price.

4. Orbitrex Peptides: Veteran-Owned, QR-Coded Batch Tracking, Finnrick A Upgrade

Orbitrex was a D on Finnrick. Then they fixed a lab-recalibration error and came back as an A across 13 tests. Vendors who survive public failures transparently are sometimes more trustworthy than vendors who have never had to explain a bad batch.

Orbitrex is based in Lewisville, TX, veteran-owned, and has been in commercial operation under 12 months. Their retatrutide ships under the brand name 3G-RT in 36mg vials. Trustpilot sits at 4.0/5 across 112 reviews, the lowest on our top-six list.

Differentiators are where Orbitrex earns its ranking. Each vial ships with a QR code that pulls the batch-specific COA when scanned. That is vial-level traceability, which nobody else on this list offers. They also run a customer testing credit program: submit your vial to an independent lab, upload the report, and Orbitrex issues either a 50% product replacement on the tested SKU or a 10% group credit toward a future order, customer's choice. The credit stacks with their bulk discount tier. Few vendors actively invite external scrutiny like that, let alone subsidize it.

The endotoxin protocol is worth a line of its own. Orbitrex runs random endotoxin testing aligned to USP <85> methods rather than testing only batches flagged for issues. Random sampling catches problems that batch-triggered testing does not.

COA scorecard.

• Completeness: Batch-specific COA accessible via vial QR code.
• Mass-spec identity: Yes.
• TFA documentation: Yes.
• Labs: Freedom Diagnostics, Chromate, and TrustPointe. Three labs, similar redundancy profile to Peptide Partners' four-lab stack.
• Finnrick: 13 tests, A rating, after the D-to-A recalibration upgrade.

The D-to-A story is worth sitting with. Most vendors who receive a bad blind-test result quietly disappear, rebrand, or dispute the result in forum threads. Orbitrex published the lab-recalibration explanation, reworked the process, and submitted for re-testing. Thirteen follow-up tests landed at A. That is a recovery arc, not a cover-up, and it is the main reason they rank above Profound despite a shorter operating history.

Weaknesses. Under 12 months commercial operating history is short. Trustpilot 4.0/5 is the lowest of our top six. The earlier D rating will still surface in searches for anyone who does not read to the end of the article.

Direct recommendation: If you want infrastructure that forces accountability (vial-level QR, customer testing credit, three-lab stack), Orbitrex is it. If you want a pristine multi-year track record, go with Peptide Partners or Ascension.

5. Profound Aminos: Best Per-Mg Pricing on 60mg Vials

If you need a 60mg vial, Profound is $4.48/mg. Everyone else is higher.

Profound Aminos lists retatrutide in 10mg, 30mg, and 60mg vials. The 20mg size is currently out of stock. Endotoxin is published as <1.0 EU/mg on every COA. Reported molecular weight is 4,731 g/mol, which is the accurate free-base mass. That last detail matters more than it looks.

COA scorecard.

• Completeness: Solid and batch-specific.
• Mass-spec identity: Yes. Reported MW of 4,731 is the correct free-base value. Vendors who report 4,845 are reporting TFA salt mass and calling it the peptide. Some vendors publish no MW at all. Profound publishes the right one, which is a calibration signal.
• TFA documentation: Yes.
• Structural detail: The COA explicitly confirms the C20 diacid fatty acid side chain. That is the albumin-binding motif that drives retatrutide's six-day half-life and makes once-weekly dosing feasible. Very few vendors bother reporting side-chain structure. Profound does.
• Endotoxin: <1.0 EU/mg documented.

Profound also lists CAS number 2381089-83-2 alongside the 4,731 g/mol free-base weight. The CAS check is another small calibration signal: a vendor that publishes the correct CAS has at least done the work to verify identity on paper. They also flag retatrutide's WADA classification transparently, which matters for any researcher with athlete populations in-frame.

Price is the headline. The 60mg vial at $269 works out to $4.48/mg, the best large-format per-mg number in our top six. Run the math against a 30mg protocol over 12 weeks: the 60mg Profound vial cuts the per-mg spend roughly in half compared to Paradigm's 50mg listing at $9/mg. For researchers running larger or longer protocols, this is where the pricing math shifts in your favor.

Weaknesses. 20mg out of stock is a real limitation if that is your preferred size. Not in the Finnrick dataset, so no blind-test corroboration. Specific lab names for the COAs are not cited on the product page, which is the main documentation gap keeping Profound out of the top three.

Size-range breadth is the quieter advantage. Profound lists six retatrutide sizes between 10mg and 60mg, more than any other vendor in our top six. For researchers who need to match exact protocol-dose increments rather than splitting larger vials or stacking smaller ones, that granularity removes compounding dosing error.

Best for: Researchers running 30mg or 60mg vials regularly, where per-mg cost compounds.

Skip if: You need multi-lab redundancy or vial-level QR traceability.

6. Paradigm Peptide: Finnrick's Top Rated, But the Honest Caveat Is Big

Paradigm Peptide has the single highest Finnrick score in the dataset for retatrutide. 9.6 average across 6 blind tests. A rating. We still rank them sixth. Here is the split.

The blind-test case is real. Six samples, 9.6 average, highest in the Finnrick dataset for this molecule. On the question of “is the peptide what the label says it is,” Paradigm scored cleanest of anyone tested.

The buyer-side case is the opposite. No COAs posted on product pages. No named third-party lab. No visible mass-spec identity data. No public TFA residual number.

Their product pages are also gated by bot-detection that blocks programmatic COA verification, so third parties cannot scrape and audit at scale. Paradigm self-describes as “highest rated RETA on Finnrick” and leans on that badge as the primary trust signal, with no secondary documentation behind it. Six Finnrick tests is also the smallest sample size of the Finnrick top three, which means the 9.6 average has the widest confidence interval of the three top-rated vendors.

Pricing does not help their case either. 20mg at $200 is $10/mg. 50mg at $450 is $9/mg. That is roughly triple Ascension's per-mg price for a vendor asking you to trust them on faith.

No Trustpilot or BBB verification surfaced in our research. That is not disqualifying on its own, but in combination with zero product-page documentation it leaves a buyer with exactly one external signal to triangulate against: the Finnrick badge.

Who should still consider Paradigm? Researchers who weight blind-test data more heavily than buyer-side documentation, researchers who run their own independent testing on every batch before use, or researchers who were already Paradigm customers before Finnrick existed and are comfortable with the track record they have built privately. We are not saying Paradigm sells bad peptide. Finnrick's data says the opposite. We are saying they ask you to trust them without showing the receipts, and our grading system does not reward that.

The verdict: Great peptide, per Finnrick. Bad transparency grade, per our four pillars. Start with vendors one through five before reaching for number six.

The Retatrutide Per-Mg Pricing Table, Compared Across All Six Vendors

Below is per-mg pricing across our top six at the most common vial sizes. We pulled these in April 2026. Prices move. The ranking relationships between vendors are more stable than the absolute numbers.

Three takeaways from the table.

1. Best large-format per-mg: Profound at $4.48/mg on the 60mg vial.
2. Best mid-size per-mg with full documentation: Ascension at roughly $3/mg on the 30mg vial with the 50% code, roughly $6/mg without.
3. Most documentation per dollar: Peptide Partners, given the four-lab stack at the 24mg format.

Broader market context: 10mg vials run $70 to $200 ($7 to $20/mg), 30mg runs $180 to $350, 60mg runs $300 to $550. Our top six all land at or below the midpoint of those ranges. No vendor wins on all three of price, documentation, and size flexibility. Pick by protocol. See our full vendor directory for ongoing scoring.

FAQ

Is retatrutide legal to buy in the US?

Retatrutide is sold as a research chemical. It is not FDA-approved for any use and it is not DEA-controlled. Vendors sell it with research-use-only labeling.

In September 2025 the FDA sent 50-plus warning letters to GLP-1 research vendors, and Amino Asylum was raided in June 2025 with its site dark since. The February 2026 Category 1 compounding restoration covered 14 peptides; retatrutide was not on that list. Those are the facts. This is not legal advice.

Why can't I get retatrutide from a compounding pharmacy?

Compounded access requires an FDA-approved drug equivalent. The February 2026 Category 1 restoration covered 14 peptides, but retatrutide was not among them. Without an approved equivalent, compounded retatrutide has no legal pathway. Compounded tirzepatide alternatives run $400 to $650 per month.

When will retatrutide be FDA approved, and what happens to research vendors after that?

Eli Lilly's NDA filing is projected for Q4 2026. FDA approval is expected late 2027 or Q1 2028. The research-chemical grey zone typically contracts after approval as regulatory risk for vendors rises sharply. The 18 to 24 month window before approval is the buying window this article is scoped to.

How do I store reconstituted retatrutide?

Lyophilized vials: refrigerated at 2 to 8°C, away from light. Reconstituted vials: refrigerated, with most vendor guidance suggesting use within 28 days. Do not freeze a reconstituted vial. General storage guidance, not a dosing protocol.

How is retatrutide different from tirzepatide?

Retatrutide (LY3437943) is a triple agonist on GLP-1, GIP, and glucagon receptors, MW 4,731 Da, still in Phase 3. Tirzepatide is a dual GLP-1/GIP agonist, FDA-approved as Mounjaro and Zepbound. TRIUMPH-4 showed retatrutide at 12mg producing 28.7% weight loss at 68 weeks versus roughly 20.9% for tirzepatide.

How can I tell if my vial contains real retatrutide and not exendin-4?

Check the observed mass field on the COA. Retatrutide free base = 4,731.33 g/mol. TFA salt = 4,845.35 g/mol. Exendin-4 = 4,186.58 g/mol.

If the observed mass does not match retatrutide within a few Da, it is not retatrutide. HPLC purity alone cannot distinguish the two, because both can register above 98% on an HPLC trace. Mass spec is the single most important COA field for identity confirmation.

For ongoing vendor scoring as market conditions change, see our full vendor directory.