GLP-1 Injection Technique

You are shown this once, quickly, by someone who does it every day, and then you go home. A year later most people have developed at least one habit that is costing them something. None of this is difficult; it is just rarely written down.

Note that devices differ. A multi-dose pen such as Ozempic uses a fresh needle each time and holds several doses; a single-dose autoinjector such as Wegovy or Zepbound is used once and discarded. Some of what follows applies only to the first kind, and I have marked which.

Where to inject

Three approved regions:

• Abdomen — at least 5 cm (2 inches) away from the navel. Most people’s default: easy to see, easy to reach, generally the least uncomfortable.
• Front of the thigh — the outer front portion, not the inner thigh.
• Back of the upper arm — awkward to do yourself, easy if someone else does it.

Absorption differences between these sites are small for this class of drug — small enough that it is not worth optimising. What matters more is consistency, because a consistent site makes a consistent weekly experience, and that makes it easier to tell whether a bad week is the dose or something else.

Avoid: scars, stretch marks, moles, bruises, anywhere tender or inflamed, and anywhere within about 5 cm of the navel.

Rotation, and the lump problem

The mistake is rotating between regions while hitting the same square inch of each one every time.

Repeated injection into the same spot causes lipohypertrophy — firm, thickened, slightly raised tissue under the skin. It is well described in people who inject insulin, and it matters for one practical reason: medication injected into that tissue absorbs erratically. People chase inconsistent effects for months without knowing why.

The fix is simple. Divide whichever region you use into quadrants, move quadrant each week, and shift by a few centimetres within the quadrant. Feel the area before you inject — if it is firm, raised, or feels different to the tissue beside it, go elsewhere and leave that area alone for 3–6 months.

The temperature thing

A pen from the fridge stings. This is the single easiest improvement available and almost nobody is told about it.

Take the pen out 15–30 minutes before you intend to use it and let it come to room temperature — a pen at 2–8°C straight from the fridge is the single most common cause of a painful injection. Do not warm it in hot water, on a radiator, or in a microwave — heat damages the medication.

The other contributors to a painful injection: pushing the plunger too fast, injecting into tensed muscle, and injecting into an overused area. Slowing down helps more than people expect.

The sequence

For a multi-dose pen:

1. Take the pen out 15–30 minutes early.
2. Check the medication is clear and colourless, and check the expiry.
3. Attach a new needle.
4. Do the flow check the instructions specify for a new pen, so you know it is primed.
5. Dial the dose. Look at the dial and confirm the number — a knocked dial is a wrong dose that nothing downstream will catch.
6. Pinch the skin if your needle length calls for it; many short needles do not need it.
7. Insert at 90 degrees, press the button, and hold for the full count specified in your instructions — commonly around six seconds — before withdrawing. Withdrawing early is the most common cause of a partial dose.
8. Remove the needle and dispose of it in a sharps container immediately.
9. Record the date, the site, and — for a new pen — the date you first used it.

For a single-dose autoinjector, steps 3 to 5 disappear. Take it out early, check the window, place it flat against the skin, press, and hold until the second click or the window changes as instructed.

Two errors that waste medication

Leaving the needle attached (multi-dose pens). The instructions say remove it after every dose, and the reason is mechanical: leaving it on lets medication leak out and air get drawn into the cartridge, so the next dose is short. If you have ever wondered why a pen ran out early, this is usually why.

Withdrawing too soon. These are viscous solutions and they take a few seconds to leave the needle. Count it out properly rather than approximating.

Normal, and not normal

The last row is rare and it is the one to know. Everything else in that table is manageable, and the red-flag list in the side-effects piece covers what else warrants a call.

Sharps

Used needles go in a proper sharps container — a rigid, puncture-resistant one with a lid, not a drinks bottle. Disposal routes vary by area: many pharmacies accept full containers, some councils collect, some clinics take them back. Ask your pharmacy when you collect your first prescription rather than working it out when the box is full.

If you are travelling, carry a small travel container and plan to bring used needles home.

Timing the injection day

One decision worth making deliberately: which day you inject. The 24–48 hours after a dose — particularly after an increase — is when tolerability is worst for most people, and once you know your own pattern you can move the injection so that window lands somewhere convenient rather than in the middle of a working week.

Most people can identify their pattern within 2 weeks of logging it, and the difficult window is typically the 24–48 hours after a dose. Changing the day is straightforward, with a minimum interval to respect — see what to do if you miss a dose.

Storage, briefly

Unopened pens live in the fridge at 2–8°C, commonly for the 2 years to their carton expiry. Once in use, most tolerate room temperature for a defined period that runs from the day of first use — not from the carton expiry date. Write that date on the pen with a marker, because by week three nobody remembers it.

Never freeze a pen. A pen that has frozen is discarded, whatever it looks like — which is also why pens never go in checked luggage.