Choosing a UK research peptide supplier: the 12-point checklist
Twelve checks UK researchers should run before ordering research peptides from any supplier: stock location, COA policy, lab independence.
There are now well over a dozen websites selling research peptides to UK laboratories, and from the product pages they look almost identical: the same compounds, similar prices, a purity claim of 98 or 99%, a stock photo of a vial. The differences that matter, whether the material was tested, whether it ships from the UK, whether anyone answers email, are not visible on the product page. This checklist is the set of questions we would want answered before ordering from anyone, including us.
The checklist
1. Do they ship from UK domestic stock?
Many "UK" peptide sites are storefronts for overseas suppliers, with material dispatched from outside the country. That means two to four weeks in transit, exposure to customs inspection and seizure, and cold-chain uncertainty. Ask directly: where does the parcel physically leave from? A UK-stocked supplier can dispatch the same day and give you tracked delivery with a next-working-day aim.
2. Do they publish a batch-matched COA you can read before ordering?
Not a "representative" COA, not a COA from a batch sold last year. The certificate for the lot you will receive, with a batch number that will match the vial label. If the answer is "we have a COA on the website", ask which batch it belongs to and whether that is the batch in stock.
3. Is the COA from an independent, named laboratory?
The analytical lab should be identifiable on the certificate by name and address. Results issued under only the supplier's own name are the supplier's claim, not independent verification. Our note on how to read a peptide COA covers what else to look for on the document itself.
4. Is the HPLC threshold stated, and is it above the industry default?
The default for "research-grade" is around 98%. That sounds high until you work out that a 98% sample carries 2% of unknown related substances, which on a 10 mg vial is 200 micrograms of material that is structurally close to the target and can confound an assay. A supplier that has raised its acceptance threshold to 99% or better, and states it, has taken on the extra purification cost. See what 99+% HPLC-verified purity actually tells you.
5. Does the chromatogram appear on the COA?
A number without the trace behind it cannot be checked. The chromatogram shows peak shape, shoulders, and how the integration was drawn. Suppliers with real lab data will send it without argument.
6. Will they email you the in-stock batch's COA before you order?
This is the single most useful test, because it takes the supplier thirty seconds if they have the document and is impossible if they do not. Send a one-line email asking for the COA for the compound and size you intend to buy. The speed and content of the reply tell you most of what you need to know.
7. Is the company UK-registered with a Companies House number?
A registered company has a legal identity, a filing history and directors who can be identified. It is not a guarantee of quality, but its absence removes any recourse. Look for the company number on the site and check it on the Companies House register.
8. Is the contact a named person rather than a shared inbox?
Procurement questions, COA requests and problem resolution go better when there is a person on the other end. Sites with only a web form and no named contact tend to be the ones that go quiet when a batch has an issue.
9. Do they reply within working hours?
Response time is a proxy for how the operation is run. A UK supplier holding UK stock should be able to answer a COA request the same working day.
10. Is the packaging vacuum-sealed?
Lyophilised peptides are hygroscopic and, for several compounds, light-sensitive. Vacuum-sealed vials in protective packaging preserve integrity in transit. Loose vials in a padded envelope do not.
11. Tracked next-day courier?
Tracking is not a luxury for temperature- and time-sensitive material. It also tells you where the parcel is dispatched from, which answers question 1 independently.
12. Is there a refund policy if purity falls short on independent verification?
The strongest signal of confidence a supplier can give is to stand behind the COA financially. Ask what happens if you have a vial independently tested and it comes back below the stated purity. The answer should be a replacement or refund, not silence.
Scoring suppliers
In our experience most UK research peptide suppliers meet four to seven of these twelve. The most common failures are questions 1, 3, 5 and 12: overseas dispatch, supplier-issued rather than independent COAs, no chromatogram, and no purity guarantee. Alphex meets all twelve, and we would rather you verify that by sending us a COA request than take the claim on trust.
A note on price
Price differences between suppliers are largely explained by what is on this list. Independent testing costs money per batch. Longer HPLC purification runs to reach a 99+% cut cost yield. UK stock costs storage. A supplier that is significantly cheaper than the field is usually cheaper because one or more of these things is not being done. That is a legitimate choice for some purposes, but it should be a visible one, not something discovered when an assay does not reproduce.
Where to go next
- How to read a research peptide COA (and how to spot a fake one)
- How Alphex tests every batch: the four-stage pipeline
- UK research peptide compliance: what suppliers and researchers can and cannot do
- Browse the Alphex catalogue and request any batch COA via the contact page
All Alphex products are supplied for laboratory and in-vitro research only and are not authorised for human or veterinary use.
Research use only. Alphex products are supplied exclusively for laboratory and in-vitro research by qualified researchers. They are not authorised for human or veterinary use, and nothing in this note is advice on any such use.
Published 2 July 2026. Alphex reviews research notes when the testing method, the catalogue or UK guidance changes.