A GLP-1 pen is simple to use once you know which kind you're holding. Pre-set pens and dial pens go wrong in different ways, so a few minutes getting to know your own pen is the easiest protection against a dosing error.
Which kind of pen do you have?
GLP-1 injections come in three main formats (our history of GLP-1 auto-injectors covers how they developed). With a single-dose pen, the dose is fixed and the pen does the injection for you. With a multi-dose pen, you attach a needle and set the dose each time. Vials need a separate syringe. Each fails differently: a pre-set pen takes the math away but depends on you having the right strength on hand, while a multi-dose pen depends on you setting the dose correctly every time.
The main brands compare like this, based on their U.S. prescribing information and instructions for use as of September 2026:
| Product | Device | Needle | Priming |
|---|---|---|---|
| Wegovy, Zepbound, Mounjaro, Trulicity single-dose pens | Single-dose auto-injector, one fixed dose | Built in and hidden | None |
| Ozempic pen | Multi-dose pen; you select the dose | Attach a new needle each time | Flow check once with each new pen |
| Wegovy FlexTouch (2.4 mg) | Multi-dose pen, 4 doses of one strength | Attach a new needle each time | Flow check once with each new pen |
| Saxenda and Victoza pens | Multi-dose dial pen for daily doses | Attach a new needle each time | Flow check once with each new pen |
| Zepbound and Mounjaro KwikPen | Multi-dose pen, 4 doses of one strength | Attach a new needle each time | Prime before every weekly injection |
| Zepbound and Mounjaro vials | Single-dose or 4-dose vial | Separate syringe and needle | Not applicable |
The KwikPen row is the one most likely to catch out people switching from a Novo Nordisk pen: its instructions say to prime before every weekly injection, where the Novo Nordisk pens need a flow check only once per new pen.
Habits that apply to every pen
Check the dose before you inject. That means confirming you're holding the right pre-set pen for your current step, or that the dose you dialed matches what was prescribed.
Follow your pen's priming instructions exactly. Where a pen has a priming or flow-check step, it clears air and confirms the pen is working, and skipping it can give you an inaccurate dose.
Rotate injection sites. Our guide on injection site reactions covers how to rotate and reduce irritation. International injection-technique guidance, written for insulin but based on the same pens and needles, also recommends the shortest pen needles (4 mm) and consistent rotation to avoid lumps under the skin (Frid et al., Mayo Clinic Proceedings, 2016, DOI (external link)).
If your pen uses screw-on needles, use a new one for every injection and put used needles in a proper sharps container.
Many people let a refrigerated pen warm up before injecting, but you don't have to. The Zepbound and Mounjaro instructions say it isn't necessary to warm the pen to room temperature (Zepbound instructions for use (external link)). The evidence that warming reduces sting is thin: in a small trial of lidocaine injections, cold and room-temperature injections hurt about the same (Lundbom et al., J Plast Surg Hand Surg, 2017, DOI (external link)). Letting a pen sit out does no harm if your label allows the time out of the fridge, but don't heat it with hot water or a microwave, which Novo Nordisk's instructions specifically warn against.
Learn your specific pen
Pen mechanics differ between manufacturers, and even between products from the same company, so the most reliable instructions are the ones that come with your prescription. A demonstration from your pharmacist or prescriber's office when you first fill it helps too. Most manufacturers also post videos for their pen. Watch the one for yours even if you've used a different GLP-1 pen before, because what you learned on one pen may not carry over.
If you're not confident with your technique
Ask your pharmacist for an in-person demonstration, even if you've been on the medication for a while. It's a common request, and it cuts the risk of the dosing mistakes covered in our guides on missed doses and accidental double dosing.
Study findings above are attributed to their authors and were located via PubMed.
This article is for general education and is not medical advice. Follow your pen's official instructions and your prescriber's or pharmacist's guidance for your specific medication.