Pens versus vials and syringes: every GLP-1 presentation and how each one is handled

Semaglutide and tirzepatide now come in more containers than most people realise, and the containers differ more than the drugs. A person who has only ever pressed a Wegovy pen to their thigh will meet a KwikPen and wonder where the button went. A person switching from a pen to a vial acquires a new job: measuring. This guide lays out each presentation on the current labels, the steps the instructions for use require, and the errors that belong to each.

The presentations on the labels

The Zepbound label lists four: a pre-filled single-dose pen, a single-dose vial, a multi-dose vial, and a single-patient-use KwikPen. The Mounjaro label lists the same four. The Wegovy label lists a single-dose pen, a single-patient-use FlexTouch multi-dose pen, and, separately, tablets. The Ozempic label describes a multi-dose pen and a single-dose prefilled syringe.

Compounded semaglutide and tirzepatide are usually dispensed as multi-dose vials, sometimes as pharmacy-filled syringes. They are not FDA approved, they are not on any of these labels, and their handling is set by the dispensing pharmacy, not by Lilly or Novo Nordisk.

Single-dose auto-injector pens

Wegovy single-dose pen. The needle is built in and hidden under a needle cover. There is no dose to dial and no priming. Pull the cap, press the pen firmly and squarely against the skin, and the injection starts when the needle cover is pressed in. The instructions say not to lift the pen until the yellow bar in the window has stopped moving; lifting early, or not pressing firmly for the whole injection, is how a partial dose ends up on the skin. When you lift off, the needle cover locks and the pen is finished. It goes in a sharps container.

Zepbound single-dose pen (and Mounjaro's). Also fixed-dose, also no priming, but with a lock ring. Pull the grey base cap straight off, place the clear base flat on the skin, turn the lock ring to unlock, then press and hold the purple button for up to 10 seconds. The instructions say to listen for two clicks, the first when the injection starts and the second when it is complete, and to check that the grey plunger is visible before lifting off. If you do not see the grey plunger, the instructions say to contact Lilly rather than inject again. Do not put the base cap back on; the instructions warn it can damage the needle.

Errors that belong to these pens. Lifting early. Not pressing the base fully flat on a curved site such as the thigh or arm. Unlocking a Zepbound pen before it is on the skin. Trying to "save" a pen after the cap is off. Attempting a second injection when a bead appears on the skin; the missed-dose rules do not cover partial doses, and a repeat risks doubling the dose. Note it and ask your prescriber.

Multi-dose pens with attachable needles

Zepbound KwikPen. Contains four weekly doses at a fixed strength. A new pen needle is attached for every injection, and the instructions say to prime before each weekly injection: turn the dose knob until you hear two clicks and see the extended line, hold the pen needle-up, press the button until it stops and a drop appears. Then dial the dose, insert the needle, press and hold for the count in the instructions, withdraw, and remove and discard the needle. The label warns never to share a KwikPen between patients, even with a needle change.

Wegovy FlexTouch pen. Also multi-dose. The instructions describe a flow check before the first dose with a new pen: turn the dose selector to the flow-check symbol, hold needle-up, press until the counter shows zero and a drop appears. For the second, third and fourth doses with the same pen you go straight to setting the dose. New needle every time; the label carries the same never-share warning.

Ozempic pen. The original multi-dose semaglutide pen. Flow check with each new pen only; new NovoFine Plus needle each time (the pack includes them, and the label says other compatible needles up to 8 mm may be used); dial the dose; insert; press and hold the dose button and count 6 seconds; then withdraw. The instructions warn that if the needle comes out early you may see a stream of medicine from the needle tip and the full dose will not have been delivered.

Errors that belong to multi-dose pens. Skipping the prime or flow check and getting a short first dose. Reusing a needle, which dulls it, raises the chance of a blocked needle and lipohypertrophy, and is against every label. Storing the pen with a needle attached, which the labels say not to do because it lets air in and drug out. Losing track of the first-use date: an Ozempic or Wegovy FlexTouch pen is discarded 56 days after first use whether or not doses remain, and the Zepbound KwikPen has its own in-use limit on the label (see storage). Sharing.

Vials and syringes

Zepbound and Mounjaro single-dose vials. Each vial holds one dose. The label says to use a syringe appropriate for the dose, for example a 1 mL syringe capable of measuring a 0.5 mL or 0.6 mL dose, and a new syringe and needle for every injection. The vial instructions say to inject exactly as your healthcare provider showed you and that your provider should tell you whether to pinch the skin. Rotation is emphasised specifically to reduce lipodystrophy and localised cutaneous amyloidosis.

Zepbound and Mounjaro multi-dose vials. Newer to the label. Several doses in one vial, with their own storage rules once opened. The measuring job is the same as the single-dose vial, repeated.

Compounded vials. The concentration is whatever the pharmacy made, and it can change from fill to fill. The FDA's page on its concerns with unapproved GLP-1 drugs describes dosing errors from patients drawing up the wrong volume and from confusion between units and millilitres, with some resulting in hospital visits. The defence is the same routine every time: read the concentration on this vial, work out the volume for the prescribed milligram dose, convert to syringe units if you are using an insulin syringe, and check the number against the pharmacy's instruction before drawing up. The calculator site's dose unit converter and its five checks before every injection exist for this. Compounded products are not FDA approved and are not interchangeable with the brand products above.

Drawing up. General technique, since the brand labels leave it to the healthcare provider: wash hands, wipe the vial stopper with alcohol and let it dry, draw air into the syringe equal to the dose volume, inject the air into the vial, invert, withdraw slightly more than the dose, tap out bubbles, push back to the exact mark, withdraw the needle. A pharmacy that dispenses vials should have shown you this in person or on video.

Errors that belong to vials. Units versus millilitres. A concentration carried over from an old vial. A syringe too large to read the dose accurately (a 0.3 mL insulin syringe reads a small dose far better than a 1 mL one). Reusing syringes. Injecting air. Using a vial past its beyond-use date.

Choosing, if you have a choice

The labels treat the presentations as delivering the same drug with similar exposure regardless of site; the choice between them is about handling, supply and cost. Pens remove measuring and most technique variables and are the presentations the trials used. Vials are cheaper on the manufacturer self-pay programs and are what compounding pharmacies dispense; they add a measuring step that must be done right every time. Multi-dose pens cut down on packaging and fridge space and add priming, needle changes and an in-use clock. The pricing site tracks what each costs; FormBlends' own tirzepatide and semaglutide pages describe the compounded vials its pharmacies dispense.

Disposal, whichever you use

Used pens, pen needles and syringes go into an FDA-cleared sharps container or a heavy-duty plastic container with a tight screw-on lid, per the FDA's sharps disposal guidance. Never into recycling, never loose in household trash, never in a bag someone else will handle. Disposal rules for full containers vary by state and municipality; the FDA page links to a state-by-state directory.