Short answer: Using a weight-loss injection pen involves these steps: letting the pen warm up briefly if its leaflet suggests it, attaching a new needle, setting the dose dial, inserting the needle into the skin at 90 degrees, pressing the button and keeping the needle in for the time your pen's instructions give so the medicine is fully delivered (on Ozempic and Wegovy FlexTouch pens, count slowly to 6 after the dose counter shows 0).

Key takeaways

  • If your pen's leaflet suggests it, a pen taken out of the fridge can be left out briefly before injecting.
  • Always attach a new, sterile needle for every injection.
  • On Ozempic and Wegovy FlexTouch pens, keep the needle in after the dose counter shows 0 and count slowly to 6; for other pens, follow the pen's instructions for use.
  • Do not press on or rub the injection site; if it bleeds, press lightly with a cotton wool pad.

GLP-1 medicines are mostly given with prefilled pens. The type of pen depends on the product: some are single-use and need no dose setting, while others are multi-dose and you select the dose for each injection. The steps below describe the common process; the instructions for your own pen always take priority.

It is recommended that you do your first injection with your GP, prescriber or another healthcare professional. This page does not replace that training.

Before injecting

  • Wash your hands.
  • If your pen's leaflet suggests it, take the pen out of the fridge and let it stand briefly before injecting.
  • Check the medicine name, dose and expiry date on the label.
  • Look at the liquid: it should be clear and colourless. If it is cloudy or has particles in it, do not use it.
  • Choose the injection site: choose it knowing which site is next in line this week.

Step-by-step injection

  • Remove the pen cap.
  • Attach a new, sterile needle; a new needle is used for every injection.
  • If your pen needs a flow check (priming), do it as the instructions describe. Most single-use pens do not need this.
  • On multi-dose pens, turn the dose selector to the dose your prescriber set.
  • Insert the needle straight into the skin and hold the button down.
  • Keep the needle in for the time stated in your pen's instructions (on Ozempic and Wegovy FlexTouch pens, count slowly to 6 after the dose counter shows 0). Withdrawing too early means part of the dose stays outside.
  • Withdraw the needle from the skin and do not rub the site.
  • Remove the needle from the pen, put it in a sharps bin and put the cap back on the pen.

Pen or vial?

Some treatments are given with a vial and syringe. In that case, the dose is read from the unit markings on the syringe, and your prescriber works out the amount. The injection technique is similar; the difference is that you draw up the dose rather than the pen doing it. Do not work out syringe units on your own.

Common mistakes

  • Pressing the button and withdrawing straight away: the full dose has not been delivered.
  • Reusing the same needle; a blunted needle increases both pain and tissue damage.
  • Injecting a cold pen straight from the fridge when its leaflet says to let it warm up first.
  • Injecting into the same spot every week.
  • Throwing used needles away with normal rubbish.

Logging your injection

Haftra logs an injection with one tap and keeps the site, dose and time together. At your next injection, it reminds you which site is next. It does not suggest doses or work out syringe units. It is free and can be used without creating an account.

iPhone, iPad and Apple Watch. Free.

Frequently asked questions

How do you use a weight-loss injection pen?

Wash your hands, let the pen stand briefly out of the fridge if its leaflet suggests it, attach a new needle, insert the needle straight into the skin and hold the button down. Keep the needle in for the time stated in your pen's instructions, withdraw it and do not rub the site.

Is the needle changed every time?

Yes. A new, sterile needle is used for every injection. Reusing the same needle increases pain and tissue damage, because the needle becomes blunt; it can also get blocked and carries a risk of infection.

Can I use the pen straight after taking it out of the fridge?

Follow your pen's leaflet. If it suggests letting a cold pen stand out briefly before injecting, do that; the leaflet also says how long the pen can be kept out of the fridge.

Can I withdraw the needle straight after injecting?

No. Keep the needle in the skin while holding the button down for the time stated in your pen's instructions. On Ozempic and Wegovy FlexTouch pens, that means counting slowly to 6 after the dose counter shows 0. Withdrawing too early means part of the dose stays outside.

Will I feel pain during the injection?

The needles are very fine, and most people feel little pain.

Sources

  • EMA: Mounjaro (tirzepatide)
  • EMA: Ozempic (semaglutide)
  • EMA: Wegovy (semaglutide)
  • NHS: Obesity treatment
  • MHRA (Medicines and Healthcare products Regulatory Agency)

Last reviewed: 4 August 2026