Short answer: Using a weight-loss injection pen involves these steps: let the pen reach room temperature, attach a new needle, set the dose dial, insert the needle into the skin at 90 degrees and press the button, then wait 6–10 seconds so the full dose is delivered.

Key takeaways

  • Letting a pen taken out of the refrigerator reach room temperature for 15–30 minutes noticeably reduces pain.
  • Always attach a new, sterile needle for every injection.
  • After pressing the injection button, wait until the counter reaches 0, and count to 6 before pulling the needle out.
  • Do not press on or rub the injection site; if there is bleeding, press gently with a cotton ball.

GLP-1 medications are mostly given with prefilled pens. The type of pen varies by 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 shared flow; the package leaflet for your own pen is what counts.

It is recommended that you do your first injection with your doctor or a healthcare professional. This page does not replace that training.

Before the injection

  • Wash your hands.
  • Take the pen out of the refrigerator and let it sit for a few minutes; cold liquid hurts more.
  • Check the medication name, dose and expiration date on the label.
  • Look at the liquid: it should be clear and colorless. Do not use it if it is cloudy or has particles.
  • Choose the injection site, knowing which site is up 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 requires a flow check (priming), do it as the instructions say. Most single-use pens do not require this.
  • On multi-dose pens, turn the dose selector to the dose your doctor set.
  • Insert the needle straight into the skin and hold the button down.
  • Wait for the time stated in the instructions (usually a few seconds). Pulling out early leaves part of the dose outside.
  • Remove the needle and do not rub the site.
  • Remove the needle and throw it in a sharps disposal container; put the pen cap back on.

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 doctor determines the calculation. The injection technique is similar; the difference is that you draw up the dose instead of the pen. Do not calculate syringe units on your own.

Common mistakes

  • Pressing the button and pulling out right away: the full dose is not delivered.
  • Reusing the same needle; a dull needle increases both pain and tissue damage.
  • Injecting right after taking the pen out of the refrigerator.
  • Injecting into the same spot every week.
  • Throwing used needles in the regular trash.

Logging the injection

Haftra logs an injection with a single tap, keeping the site, dose and time together. At the next injection, it reminds you of the next site. It does not suggest doses and does not calculate syringe units. It is free and can be used without an account.

iPhone, iPad and Apple Watch. Free.

Frequently asked questions

How do you use a weight-loss injection pen?

Wash your hands, take the pen out of the refrigerator and let it sit for a few minutes, attach a new needle, insert the needle straight into the skin and hold the button down. Wait for the time stated in the instructions, then remove the needle 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 is not safe: the tip gets dull, it can clog, and it increases pain, tissue damage and the risk of infection.

Can I use the pen right after taking it out of the refrigerator?

Take the pen out of the refrigerator and let it sit for a few minutes; cold liquid hurts more.

Can I pull the needle out right after pressing the button?

No. Keep the needle in the skin while holding the button down for the time stated in the instructions (usually 6–10 seconds). Pulling out early lets part of the dose leak back out.

Will I feel pain during the injection?

The needles are micro-needles (31G–32G) in thickness; when the medication is at room temperature, there is almost no pain.

Sources

  • EMA - Mounjaro (tirzepatide)
  • EMA - Ozempic (semaglutide)
  • EMA - Wegovy (semaglutide)
  • NHS - Obesity treatment
  • U.S. Food and Drug Administration (FDA)

Last reviewed: August 4, 2026