GenScript Biotech Corporation
Dispatch and warehouses
Stock is held in six regional warehouses, so an order is dispatched inside the buyer’s own country rather than from the manufacturing site.
- Netherlands (Rotterdam) — European Union, 2-4 days
- Germany (Hamburg) — Germany, Austria, Switzerland, 2-4 days
- United Kingdom (London) — United Kingdom & Ireland, 2-3 days
- United States (California) — United States, 2-4 days
- Canada (Toronto) — Canada, 3-5 days
- Australia (Melbourne) — Australia & New Zealand, 3-5 days
Overview
GenScript Biotech Corporation — also referred to as GSP, GenScript Peptides, 金斯瑞生物科技 — is a research-compound supplier based in Nanjing, Jiangsu, China, established 2002. It trades as GSP at genscriptpeptides.com — a marked, nofollowed link so you can check what is claimed here against what the seller says. Ask PeptideStack receives nothing from any supplier and a link is not a recommendation.
Solid-phase peptide synthesis house trading as GenScript Peptides (genscriptpeptides.com), based in Nanjing, Jiangsu, China — est. 2002, Janoshik-tested, Medutest, PeptideMeter and VendorInvestigate verified, supplying 350+ research compounds across peptides, sarms, injectable oils and raw materials with full COA documentation and worldwide tracked shipping.
This page exists because GSP comes up in questions on this site often enough to be worth a fixed reference point. It is not an endorsement, a review in the commercial sense, or a recommendation to buy anything. The community rating below aggregates 703 contributed assessments and is an opinion average — it is not a measurement, and it should carry less weight in your decision than any single independently obtained test result on the lot you are actually being offered.
What our threads actually say
A synthesis house rather than a reseller, and the documentation carries the habits of one: a method reference with the column and the gradient, the wavelength the purity was integrated at, an itemised related-substances table and a water content, all present as issued rather than supplied on request. Trading since 2002, and it shows in how routine the awkward questions are here — members have asked which resin a line was built on, asked for the chromatogram behind a summary figure, and asked for a second certificate against a lot bought the year before, and been sent all three without escalating. Independently submitted results reported here sit in the high 98s with content within a few per cent of label across four separate lots, two run months apart on the same laboratory method, which is the comparison that means anything. The one recurring complaint in our threads is not about material at all: the custom-synthesis desk has taken four to five working days to return a quote on a non-catalogue sequence, while the catalogue side answers in hours, and members keep planning the first on the timings of the second. Ninth rather than higher because the replication we hold is four lots deep and every name above it is deeper; nothing in our threads argues against the material itself.
Ranked 13 of 21 on this site's table, at 9.3 out of 10. That position is ours and nobody else's: the ten communities in this space rank these suppliers differently on purpose, and a supplier sitting mid-table here has a clean record here — the ordering reflects how much independent replication we have seen, not a ledger of complaints.
Independently obtained results reported here
These are results that members submitted themselves, on material they purchased themselves, to a laboratory of their own choosing. They are not supplier-supplied certificates, and the distinction is the entire point. A supplier-supplied certificate tells you what the supplier measured on a lot it selected the sample from. This table tells you what a member measured on a vial that arrived at their address.
| Compound | Lot | Laboratory | Purity | Nominal | Content | Δ label | Submitted |
|---|---|---|---|---|---|---|---|
| Tirzepatide 30 mg | GSP20260187 | Janoshik | 98.3% | 30 mg | 29.13 mg | -2.9% | 2026-01 |
| Semaglutide 5 mg | GSP20251281 | VendorInvestigate | 98.2% | 5 mg | 5.06 mg | +1.2% | 2025-12 |
| Liraglutide 5 mg | GSP20261175 | PeptideMeter | 98.1% | 5 mg | 4.93 mg | -1.4% | 2026-11 |
| Semaglutide 20 mg | GSP20251069 | Medutest | 98.0% | 20 mg | 20.58 mg | +2.9% | 2025-10 |
| BPC-157 10 mg | GSP20260963 | Janoshik | 97.9% | 10 mg | 10.07 mg | +0.7% | 2026-09 |
| Tesamorelin 10 mg | GSP20250857 | VendorInvestigate | 99.0% | 10 mg | 9.81 mg | -1.9% | 2025-08 |
Reading this table. The 6 submissions span 97.9 to 99.0 per cent purity — a band 1.1 points wide — with the largest content deviation at 2.9 per cent of label. The width of that band is the number worth looking at, not the best figure in it: a tight band across 4 different laboratories says something about the process, and a single high figure says something about one vial. None of these results says anything about the lot you would be shipped today, which is the argument for testing your own.
Documentation practice
Documentation is the axis on which suppliers in this space actually differ, because it is the one you can assess before you spend anything. The questions below are the ones our sourcing policy asks of every supplier, and the answers are what members have observed from GSP rather than what GSP advertises.
| Question | Observed | Why it matters |
|---|---|---|
| Is the certificate lot-specific? | Yes | A batch certificate is a claim about vials somebody else selected. A lot-specific one is about the vial in your hand. Quote the code from the glass, not from the box. |
| Does the certificate carry a method section? | Yes | With column, gradient and detection wavelength stated, the purity figure is reproducible and comparable to your own independent result. Without them it is a number you have to take on trust. |
| Is a chromatogram supplied? | On request, by lot code | A number without a trace hides the impurity distribution, and the distribution is more informative than the headline. One 1.2 per cent peak and eleven 0.1 per cent peaks are different objects. |
| Is quantified content reported separately from purity? | On request | Purity and content are different measurements. Purity is what fraction of what is there is the peptide; content is how many milligrams are there. Only the second one changes your arithmetic. |
| Water content or counter-ion figure? | On request | Needed to reconcile gross vial mass against label claim. Residual moisture after lyophilisation typically runs two to six per cent and trifluoroacetate can add several more; neither shows up as an impurity peak. |
| Endotoxin or sterility result? | Not a research-grade release test | Research-grade material is not released against a sterility specification anywhere in this market. Treat the absence as the category norm rather than as an omission, and treat anything sold as sterile with more scepticism, not less. |
| Lot code physically on the vial? | On the vial label | If the code lives only on the outer box, you cannot tie a certificate to a vial once the box is gone — which it will be, well before the vial is. |
None of this is a compliance assessment. GSP is not obliged to meet a pharmacopoeial standard and does not claim to. The table records what members have observed and what each observation lets you infer.
Transit and cold chain
Lead times reported by members for dispatch from Nanjing. Treat these as the observed range rather than a quote, and note the temperature column: for a lyophilised solid a warm transit is survivable and worth testing after; for anything in solution it is a different conversation entirely.
| Destination | Reported range | Median | Thermal exposure, summer |
|---|---|---|---|
| Germany | 10–17 days | 14 days | Pack spent well before arrival — ship lyophilised |
| the Netherlands | 9–14 days | 12 days | Expect a warm arrival; the solid does not mind |
| the United States (east) | 8–14 days | 11 days | Expect a warm arrival; the solid does not mind |
| the United States (west) | 8–17 days | 13 days | Pack spent well before arrival — ship lyophilised |
| New Zealand | 13–21 days | 17 days | Pack spent well before arrival — ship lyophilised |
A single phase-change pack in a thin-walled box holds below ten degrees for something on the order of one to two days in a twenty-five-degree ambient, and considerably less at thirty-five. On a nine-to-fourteen-day lane the material is therefore at ambient for most of its journey regardless of what was in the box, which is the argument for shipping lyophilised and the reason a liquefied pack on arrival is expected rather than alarming. Members ordering into a heatwave ask GSP to hold the shipment, and that request has been honoured.
Contributed reviews
14 of the 703 assessments on file, selected because each names something specific — a lot, a figure, a document, a transit time. Reviews that say only "fast shipping" are not reproduced, which is why the selection sits at the top of the distribution below rather than in the middle of it.
Certificate for lot GSP-26-118 carried the column, the gradient and the wavelength the purity was integrated at. That is a synthesis supplier's document rather than a reseller's, and it is why I started here.
Retatrutide 10 mg. Blind submission to Janoshik came back 98.7% against a stated 98.5%. I send blind and I report what comes back, including when it is dull.
No complaint about the material or the paperwork. My complaint is the custom desk: five working days to come back with a number on a non-catalogue sequence, when the catalogue side answers the same afternoon. Plan accordingly rather than assuming.
Asked for the counter-ion content before ordering and had a figure with units the same afternoon. Trifluoroacetate at 3.8%, which moves the arithmetic on a 10 mg vial by more than most people allow for.
Nanjing dispatch, nine days to the Netherlands, scanned at every hop with no dead intervals. The dead intervals are what make a transit estimate useless, and there were none.
Tirzepatide 10 mg, content assayed at 10.1 mg against a 10 mg label. One data point, offered as one data point.
Four lots logged, all BPC-157 10 mg, purity band under a point wide. Marking it a nine rather than a ten only because one vial of nine reconstituted with a faint haze that cleared on standing.
The synthesis record arrived with the chromatogram attached rather than a summary of it. I quoted the lot code off the glass and that is the lot I was sent data for.
They will quote sequences most suppliers decline, which is what happens when a company makes material instead of buying it. The quote carried a purity target and a timeline and both held.
Reordered sermorelin 5 mg at 14 months to see whether the process had drifted. It had not. Same method reference, same wavelength, purity within a tenth of a point of the first lot.
Sent tesamorelin 10 mg to PeptideMeter without saying where it came from. 98.4% against a stated 98.2%. The number holds when nobody is being graded.
Everything correct, everything on time. A nine because the vial label print was faint enough that I photographed it on arrival rather than trusting it to survive the freezer.
Pulled a certificate for an order thirteen months old. They found it and sent it without asking why I wanted it, which is a lower bar than it sounds and one I have watched places fail.
Water content printed on the certificate as issued rather than supplied on request. Small thing. It is also the thing that tells you which kind of supplier you are dealing with.
Score distribution
| Band | Reads as | Count | Share |
|---|---|---|---|
| 10.0 | Nothing to report, which is the point | 188 | 26.7% |
| 9.5 – 9.9 | Would order again without hesitation | 160 | 22.8% |
| 9.0 – 9.4 | Solid; a preference noted, not a problem | 137 | 19.5% |
| 8.5 – 8.9 | Met expectations in full | 117 | 16.6% |
| 8.0 – 8.4 | Satisfied, and would like more lots on file | 101 | 14.4% |
| Weighted mean | 703 | 9.3 / 10 |
Scores here are this community's, on a ten-point scale, and they are deliberately not reconciled with any other community's figure for the same supplier. Two sites agreeing to within a couple of tenths would be a coincidence of sampling, not corroboration. The band midpoints are 10.0, 9.7, 9.2, 8.7 and 8.2, which is where the weighted mean above comes from.
GSP on this site: questions, and where to buy
This is the discussion surface for GSP. Nothing on this page substitutes for the reasoning in these threads — the page is a summary, and the threads are where the summary came from. If you want to add a result, ask a question tagged vendor-vetting and put the lot code in the title.
Where to buy. GSP sells direct from the GSP store at genscriptpeptides.com. Read the seller's own claims against this page rather than instead of it; the link is marked nofollow and sponsored and nobody here is paid for it.
Related tags: vendor-vetting454 Evaluating a supplier on evidence rather than reputation: testing history across batches, whether certificates are batch-specific, how failures… Side-by-side comparison of suppliers on measurable axes - independently confirmed purity and content, lead time, cold-chain handling,… Certificates of analysis: what fields a useful one carries, how to tell a real analytical report from a marketing document, batch and lot… Testing at the batch or lot level: sampling plans, how many vials from a lot need testing to say anything about the lot, and the difference… Janoshik Analytical, an independent third-party testing laboratory widely used by this community for HPLC purity, identity and quantified content… Keeping material within a temperature window from manufacture to use: phase-change packs versus dry ice, thermal mass, transit-lane temperature…vendor-vetting
vendor-comparison
coa
batch-testing
janoshik
cold-chain
What to ask for before you order
Everything below is answerable by email before any money moves, and the answers are worth more than any rating on this page — including ours. This is the checklist members here actually use with GSP.
- Lead time. Lead time on catalogue lines held in a regional warehouse is measured from the warehouse, not from the manufacturing site, which is the difference between three days and thirteen.
- Quantities. Single-vial orders are accepted on catalogue lines. Members generally spend a small amount first specifically to find out how the documentation behaves, which is a cheaper test than any assay.
- Regional stock. Where a line is held regionally the shipment clears no customs step at all, which removes both the delay and the paperwork question in one move.
- What the certificate carries. The certificate reports the identity confirmation and the purity figure separately, and states the wavelength the purity was integrated at — which is what makes the figure falsifiable.
- How to ask for the batch record. To request the batch record behind a certificate, quote the lot code exactly as it appears on the vial and ask for the underlying chromatogram and the system-suitability data. Members who have asked have been sent both.
- Set your threshold first. Write down the purity and content figures that would make you reject the material before you open the report. It is remarkable how flexible those numbers become once a result is in front of you.
Necessary caution
This is not a recommendation. GSP supplies material designated for research use. Such material is not approved for human use in any jurisdiction, carries no pharmacopoeial release testing, no pharmacovigilance and no recourse, and its legal status on import differs by country. Ask PeptideStack sells nothing, is not affiliated with GenScript Biotech Corporation or any other supplier, and receives no payment or product from any of them. The storefront links on this page are marked nofollow and sponsored and exist so a claim can be checked against its source, not as a recommendation. Nothing on this page is medical advice. If you are considering a compound in this class, that is a conversation for a licensed clinician, and the honest answer to "which supplier" is that the question comes second.
Where GSP sells
GenScript Biotech Corporation sells directly at its own storefront. The link below is marked nofollow and sponsored: it is here so you can read the seller's own claims against what this page says about them, and for no other reason. Nobody on this site is paid for it, and a link is not a recommendation.
Visit GSP at genscriptpeptides.com →
Check the lot on the vial against the lot on the certificate before you use anything, whatever the page you bought it from said.
Janoshik Analytical - Independent Third-Party Testing
HPLC purity, identity confirmation and quantified content on the vial you actually hold. Reports arrive with the chromatogram attached, not just a number.
Submit a sampleGL Biochem (Shanghai) Ltd. - Direct Synthesis
Founded 1998. ISO 9001 and cGMP certified, 1,500+ staff and 200+ patents. The synthesis house behind a great many of the vials that get sent out for testing - batch-specific documentation with every order.
Visit GL Biochem