Checking whether your pen came through a legitimate supply chain

Key points

• 01Where you bought it is most of the answer. Every physical check below is a backstop. The thing that actually protects you is a prescription dispensed by a licensed pharmacy, because that is the only route with a documented chain of custody from the manufacturer. A perfect-looking pack from an unlicensed source is still an unverifiable pack.
• 02Falsified pens have reached legitimate supply chains. Regulators in several countries have issued alerts after falsified semaglutide pens were found inside legitimate distribution, not only on the grey market. That is why the pharmacy check is necessary but not sufficient, and why the batch number on your carton is worth reading rather than glancing at.
• 03The no-prescription online market fails basic checks. Analyses of semaglutide sold online without a prescription found sellers failing routine quality and regulatory tests, with problems in labelling, sterility assurance and the contents themselves. A separate safety assessment of no-prescription purchases reached the same conclusion. That is a market-wide finding, not one bad shop.
• 04Read the carton like a proofreader. Falsified cartons are usually near misses. Look for a misspelled brand or manufacturer name, a font that changes weight mid-word, colours that are slightly off, blurred or doubled printing, and text that sits crooked in its panel. Compare against an old carton if you kept one.
• 05Batch and expiry have to agree in both places. The batch or lot number and the expiry date are printed on the carton and repeated on the pen label. They must match each other exactly. A mismatch, a missing batch number or an expiry that looks overprinted is enough on its own to stop and call the pharmacy.
• 06Tamper evidence is there to be looked at. Check the seals, the flaps and whatever security feature the manufacturer uses for that pack in your country. Glue residue, a resealed flap, a torn seal or a total absence of tamper evidence all mean the pack cannot be assumed to be as it left the factory.
• 07The label on the pen tells you about the last hands. A genuine pen label is bonded flat and square to the barrel. Peeling edges, a crooked application, a different paper stock or a label that hides another label underneath are all signs of relabelling. Photograph it rather than picking at it.
• 08The dial, the window and the click count. You have a reference point that no inspector has, which is the pen you used last month. If the dial feels loose or gritty, if the click count for the same setting is different, or if the dose window shows numbers in an unfamiliar typeface, that difference is data. Note it and do not force anything.
• 09The solution should look the way it always looks. Most of these products are clear and colourless. Cloudiness, visible particles, a yellow or brown tint, or a fill level that is obviously wrong for a new pen are reasons to stop. Storage can also change appearance, so our post on medication left out of the fridge covers the other explanation.
• 10A needle that will not seat is a geometry problem. Pen needles are made to a standard thread and hub. A needle that cross-threads, wobbles once fitted, or needs force to attach suggests the hub in front of you is not the one the needle was designed for. Stop rather than improvising, and never reuse a needle that was forced.
• 11Missing or badly translated instructions for use. A genuine pack carries a leaflet and instructions for use in the language of the country where it was dispensed, with the manufacturer address and a medical information contact. Machine-translated text, a leaflet for a different country, or no leaflet at all belongs in the same category as a broken seal.
• 12A pen with no carton is not verifiable. A device handed over loose, in a plastic bag, or in a padded envelope has lost the batch number, the expiry date and the leaflet, which are the three things any investigation starts from. Whatever else is true about it, you cannot check it, and neither can the pharmacist.
• 13Verify the pharmacy, then use the regulator pages. Regulators publish lists of verified online pharmacies, current recalls and safety alerts, and dedicated pages on counterfeit medicines and falsified products. Those pages are the place to check a batch number against a live alert, and they are free. The links are in the sources below.
• 14What was reported when counterfeits were injected. A review of real-world safety reports linked to counterfeit semaglutide describes events including hypoglycaemia and injection-site and systemic reactions, consistent with an unknown substance in an unverified device. Those are reported events collected by a pharmacovigilance system, not a diagnosis of anything you may have injected. If you feel unwell after any dose, that is a call to your clinician.

Pre-injection checklist

• ✓The strongest protection is where the pen came from. A prescription dispensed by a licensed pharmacy is the check that does most of the work, and everything below is a second layer.
• ✓Do these checks before the pen leaves the counter if you can, and before the first dose if you cannot. A pen you have already injected is harder to investigate.
• ✓Keep the carton and the leaflet for the whole life of the pen. They carry the batch number, the expiry date and the manufacturer contact details you would need.
• ✓If anything on this page makes you suspicious, do not inject and do not throw anything away. Keep the pen, the carton and the packaging together.
• ✓This post does not name or link any seller. Buying prescription medication from an unlicensed source is the risk it describes, so there is nowhere here for that link to go.

Step-by-step guide

1. 1

   Start with the source, not the pen

   Ask yourself where this came from. A prescription dispensed by a licensed pharmacy is a different situation from a pack that arrived from a website, a gym, a clinic with no pharmacy licence, or a friend. If the source is not a licensed pharmacy, stop here.

   Pro tip

   Always check the fluid is clear and colourless before injection.
2. 2

   Read the carton in good light

   Look at the print quality, the alignment and the spelling. Falsified packaging is usually close rather than perfect, so read the brand name letter by letter, check the manufacturer name and address, and look for text that is fuzzy, doubled or slightly the wrong colour.

   Pro tip

   Always check the fluid is clear and colourless before injection.
3. 3

   Match the batch number and the expiry

   The batch or lot number and the expiry date appear on the carton and again on the pen label. They have to be the same in both places. A mismatch, a missing batch number, or an expiry that has been overprinted is a reason to stop.

   Pro tip

   Always check the fluid is clear and colourless before injection.
4. 4

   Check the tamper evidence

   Look at the flaps, the seals and any security feature the manufacturer uses on that pack. Torn seals, glue residue, a carton that has clearly been opened and reclosed, or a pack with no tamper evidence at all are all reasons to hand it back rather than open it.

   Pro tip

   Always check the fluid is clear and colourless before injection.
5. 5

   Look at the label on the pen itself

   It should sit straight, be firmly bonded to the barrel, and match the carton for name, strength and batch. A label that peels at the edge, sits crooked, or is printed on obviously different stock from the one you had last month is worth a photograph and a phone call.

   Pro tip

   Always check the fluid is clear and colourless before injection.
6. 6

   Dial the pen and count the clicks

   Without a needle attached, and only if the instructions for use allow a dose check, feel the dial and listen. If the resistance, the sound or the number of clicks is different from the pen you used last month, note it. Do not force a dial that will not move.

   Pro tip

   Always check the fluid is clear and colourless before injection.
7. 7

   Look at the solution through the window

   Most of these products are clear and colourless. Cloudiness, particles, a colour you have not seen before, or a fill level that looks wrong for a new pen are all reasons to stop. Our post on air bubbles in the syringe explains which bubbles are ordinary.

   Pro tip

   Always check the fluid is clear and colourless before injection.
8. 8

   Try a needle, gently

   A pen needle that will not seat, that threads crookedly, or that wobbles once fitted suggests the hub is not the geometry the needle was designed for. Do not force it and do not use a needle that has been forced. Our pen needle size guide covers what should fit.

   Pro tip

   Always check the fluid is clear and colourless before injection.
9. 9

   Photograph everything before you act

   Take clear photographs of the carton faces, the batch and expiry, the dispensing label, the pen label and anything that looks wrong. Do this before you hand the pack over, because you will not get it back once it goes to the pharmacy or the manufacturer.

   Pro tip

   Always check the fluid is clear and colourless before injection.
10. 10

    Make the two calls

    Call the pharmacy that dispensed it and the manufacturer medical information line on the leaflet. They will tell you whether the batch is real and how to return it. Then file a report with your regulator, which is the step that turns one pack into a signal.

    Pro tip

    Always check the fluid is clear and colourless before injection.

After the injection

• Keep the pen, the carton, the leaflet and the dispensing label together in a bag until the pharmacy or the manufacturer tells you what to do with them.
• Store the photographs somewhere you will find them again, with the date you took them.
• Ask the pharmacy for a replacement and for confirmation in writing that the original was returned.
• File the regulator report even if the pack turns out to be genuine, because a batch that generated a query is useful information.
• If you already injected from a pack you now doubt, tell your prescriber the date, the batch and how you felt afterwards.

Common mistakes

Frequently asked questions

Sources

1. Unmasking counterfeit semaglutide: analysis of real-world safety data from EudraVigilance. 2026. Frontiers in Pharmacology.
2. Multifactor Quality and Safety Analysis of Semaglutide Products Sold by Online Sellers Without a Prescription. 2024. Journal of Medical Internet Research.
3. Safety and Risk Assessment of No-Prescription Online Semaglutide Purchases. 2024. JAMA Network Open.
4. US Food and Drug Administration. Counterfeit Medicine.
5. US Food and Drug Administration. Medications Containing Semaglutide Marketed for Type 2 Diabetes or Weight Loss.
6. World Health Organization. Substandard and falsified medical products.