What peptides and GLP-1s are, and what to log if you're prescribed one

What is a peptide, and what is a GLP-1?

Longetic stores what you were prescribed and when you took it, not what the molecule is. A peptide is a short chain of amino acids, and GLP-1 is a hormone your own gut releases after you eat. The medicines people mean when they say GLP-1 are not the hormone itself, they act on the same receptor it does.

The National Human Genome Research Institute glossary puts the first half plainly. "A peptide is a short chain of amino acids (typically 2 to 50) linked by chemical bonds (called peptide bonds)." The same entry draws the line to the next size up: "A longer chain of linked amino acids (51 or more) is a polypeptide." So "peptide" is a description of shape and length, not a category of medicine, and nothing about the word tells you whether a particular product is approved, tested or legal where you live.

The second half is a hormone you already make. The MedlinePlus Medical Encyclopedia, reviewed on 18 May 2026, states it in one sentence: "Glucagon-like peptide-1 (GLP-1) is a natural hormone that is released by your gut after a meal." The Society for Endocrinology's public resource in the UK says the same thing independently, in a page last reviewed in July 2021: "Glucagon-like peptide 1 is a hormone produced in the gut and released in response to food." Two publishers, two countries, five years apart, the same three facts.

Why do a hormone and a medicine share the same name?

Because the medicine is named after the receptor it acts on, not after itself. Regulators call this class a GLP-1 receptor agonist, a statement about mechanism, and that is the reason a single phrase covers products with different brand names, different approved uses and different legal status in each country. The shared name hides those differences rather than explaining them.

The US prescribing information for one semaglutide product, revised in January 2025, describes the substance in its clinical pharmacology section as acting "as a GLP-1 receptor agonist that selectively binds to and activates the GLP-1 receptor". The Highlights section of the same document names the class directly: the product "is a glucagon-like peptide 1 (GLP-1) receptor agonist".

One small thing worth knowing if you ever compare two official documents side by side. The US label prints the class as "glucagon-like peptide 1", with no hyphen before the numeral; the European Medicines Agency writes "glucagon-like peptide-1", with one. The two agencies are describing the same thing. A difference in punctuation between regulators is not a difference in substance, and it is not a reason to think you are reading about two different products.

What are these medicines approved for, and does that change by country?

Yes, and the differences are not cosmetic. What a product is approved for, and whether it is approved for weight management at all, is decided separately by each regulator, so one brand can be licensed for one use in one country and for another use elsewhere. The only reliable way to know is to read the document your own country's regulator publishes, and to note the date printed on it.

The clearest illustration is that the US label for one widely discussed semaglutide product carries no weight-loss indication at all. Its first indication reads "as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus", and its other two are risk-reduction uses that each add a further restriction on who they apply to. Weight management for semaglutide sits with a different brand and a separate authorisation. People talk about "the drug" as if there were one; the paperwork says otherwise.

Two of those rows are worth reading in full. The NHS page on tirzepatide, last reviewed on 15 May 2026, says: "It's only available with a prescription, either NHS or private." The "or private" matters, and a summary that stops at "prescription" loses it. On 22 May 2026 the European Medicines Agency announced a committee opinion on an oral form for weight management and noted its status carefully: "The opinion adopted by the CHMP is an intermediary step on Wegovy tablets' path to patient access." It also said plainly that the tablets "will only be available with a prescription".

What do regulators say about these products sold outside a pharmacy?

All four of the regulators below have published warnings, and the striking thing is that no two of them use the same word. One says unapproved, one says falsified, one says counterfeit and not authorised, one says illegal. The words are not interchangeable, they describe different legal findings, and carrying one country's term into another country's sentence makes the claim wrong.

This is not a pedantic distinction. "Compounded" is a US regulatory category with its own rules and does not describe anything on sale in England or Spain. "Falsified" is the European term for a medicine misrepresenting its identity or origin. "Not authorised" means a regulator has never licensed the product in that country, which is a different problem from a licensed product being faked.

The UK entry is the most recent of the four. In a news story dated 15 October 2026, the MHRA and West Midlands Police said "Fake weight loss medicines worth approximately £2 million were seized last night" and that these products "have not been assessed for safety, quality or effectiveness". The same page carries a separate and narrower finding about one substance: "Retatrutide has not been authorised for use in the UK." It adds the clause that makes the sentence accurate rather than absolute, that products sold as retatrutide "outside legitimate clinical trials are being supplied illegally". The agency's advice is that "Anyone considering GLP-1 treatment should speak to a healthcare professional". Separately, it says to "only obtain medicines from a registered pharmacy against a valid prescription".

Spain's regulator, the AEMPS, published its own note on 3 September 2025 and reached for a different word. Its line on how these products are sold is short and worth quoting as printed: "En España, y en muchos estados de la UE, la venta online de medicamentos con receta es ilegal." The page does not use the word "falsificados" anywhere, which is why the table above records Spain's term as illegal rather than falsified. On the other side of the Atlantic, the US position on products labelled for laboratory use is set out in an FDA warning letter dated 17 June 2026, which found that despite labelling marketing products for "RESEARCH USE ONLY" and "not for human consumption", the evidence "establishes" "that your products are intended to be drugs for human use". An FDA page current as of 1 October 2026 makes the consumer-facing version of the same point: such products are "falsely labeled "for research purposes" or "not for human consumption."" and "These products have been sold directly to consumers for human use with dosing instructions."

What should you write down if you are prescribed one?

Write the name and strength exactly as printed on the box, the batch number, the expiry date, the date you started, and anything you noticed afterwards with the date it began. That is not a wellness habit. It is close to the exact list that an official safety-report form asks a patient to supply, so the home record and the official form end up wanting the same information.

In Spain the fields are published and anyone can read them. The AEMPS manual for its NotificaRAM reporting form, dated 18 December 2025, reproduces the citizen version of the form field by field. Among them: "Nombre del medicamento", "Lote", "Fecha de caducidad", "¿Cuándo empezó a utilizarlo?", "Síntomas de la reacción adversa", "¿Cuándo han empezado esos síntomas?" and "¿Cuándo han terminado los síntomas, si es que han terminado?". A batch number and an expiry date are not things anyone remembers. They are on the box, and once the box is gone they are gone with it. The same goes for the paperwork from the appointment itself, which we cover in what to keep after a doctor visit.

England asks for broadly the same material, but publishes the field list in guidance written for clinicians rather than for patients, which is a real asymmetry between the two countries. The patient-facing Yellow Card pages instead make the threshold clear, and the threshold is low. "You can report a side effect anytime, even if you are no longer using the medicine." The guidance for professionals, patients and the public, last updated on 24 July 2025, puts the standard in one line: "You do not have to prove causality to report a suspected ADR, only a suspicion is needed." The scheme is open to patients, parents and carers, and it says so: "You can report for yourself or for someone else, with their permission."

Both countries also tell you to bring the whole list, not just the new thing. NHS guidance for patients, on a page whose own next review date of 12 January 2026 has passed, says: "List or bring all your medicines and pills – including vitamins and supplements." Spain's Ministry of Health, in a March 2022 guide for health professionals built on a WHO tool for patients, lists it as a question for the patient to ask themselves: "¿Mantengo una lista actualizada con todos los medicamentos y productos que tomo?" If more than one clinician prescribes for you, the same logic extends to keeping one medication list when several doctors prescribe. There is also a practical reason beyond tidiness. MedlinePlus, reviewed on 25 January 2026, notes that "The vitamin biotin (B7) can affect the results of the TSH test" and advises: "If you take biotin, talk to your provider before you have any thyroid function tests." It pairs that with a warning the article repeats deliberately: "Do not stop taking any medicines without first asking your provider."

Does anyone officially tell you to log the date and site of an injection?

In the United States, yes, and in patient-facing materials. In England and Spain the official patient leaflets reviewed for this page tell you to change the injection site, but none of them tells you to write down where or when. That gap is not a reason to skip the habit, only a reason to know that if you keep that record, you are keeping it on your own initiative.

The US instruction is explicit and it is written for the person doing the injecting. A MedlinePlus patient-instruction page, reviewed on 15 July 2024, says: "Write down the date, time, and place on the body where you put the injection." A MedlinePlus drug-information page for a different injectable, last revised on 15 May 2025, says: "Keep a record of the date and spot of each injection." The FDA-approved Instructions for Use for a generic version of that product, revised in February 2025, ask for the sites specifically: "Keep a record of the sites where you give your injection each day so you will remember where you already injected."

We looked for the same instruction in English and Spanish national patient guidance and did not find it. The pages read were the NHS medicines page for an injectable treatment, the NHS page on side effects of an injectable, the NHS guidance on what to ask your doctor, the NHS page on blood tests, NHS England's guidance on medication safety, the Specialist Pharmacy Service page on medication review, and the AEMPS patient leaflet for an injectable product in the CIMA database. The Spanish leaflet does say "Cambie el sitio donde se inyecta regularmente." It does not say to record it. Local hospital leaflets may well say more, but they are not national guidance, and this page only reports what the national sources print. The honest conclusion is narrow: changing the site is official advice in both countries, writing it down is official advice in neither.

So the list is yours to keep, and the only question is where. A sheet of paper works, and so does a note on a phone, as long as the dates survive. As a disclosure, Longetic is our product, so weigh this accordingly: it holds a dated medication list with dose reminders and a schedule, alongside your lab reports and your doctor visits, so that the name, the strength and the start date are in the same place as everything else when somebody asks. It does not check interactions, it does not interpret anything, and it has no injection log, so the site and the date still go in whatever you already use. What matters is not the tool. It is that the record exists, dated, before the appointment where somebody asks you for it.

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