How to Inject GLP-1 Drugs: Technique, Sites, and Common Mistakes

GLP-1 weekly injections are subcutaneous — into the fat layer under the skin — not intramuscular or intravenous. Correct technique is straightforward and becomes routine within a few doses. For the full step-by-step pen walkthrough with Wegovy-specific instructions, see the semaglutide injection guide.

Equipment

Pre-filled autoinjector pens (Wegovy, Zepbound KwikPen, Ozempic, Mounjaro): Single-use pens with a needle already attached (or a needle cap to be attached per the pen-specific instructions). No syringe required. Press and hold to inject.

Vials with separate syringe (Zepbound single-dose vials): Zepbound is available as individual vials through LillyDirect. These require drawing the medication into a syringe before injection. Vials are often used by patients who prefer more control over the injection or who are familiar with syringe use.

Needle gauge: 30–32 gauge (very fine), 4–8 mm length. These are specifically designed for subcutaneous injection and are substantially smaller than standard intramuscular needles.

Approved injection sites

All current weekly GLP-1 injectable drugs share the same approved injection sites:

1. Abdomen: At least 5 cm (2 inches) from the navel. The lower abdomen is most commonly used — pinch a fold of skin away from the navel. Do not inject at the navel itself (the umbilicus is a different tissue layer).

2. Outer upper thigh: The lateral aspect of the thigh (outer side). Avoid the inner thigh.

3. Outer upper arm: The posterior or lateral aspect of the upper arm. This site is harder to self-inject; some patients use a mirror or have a partner assist.

Rotation: Use a different site each week. Within the same anatomical area, vary the specific spot by at least 2–3 cm from the prior injection point. A systematic rotation pattern (e.g. right abdomen → left abdomen → right thigh → left thigh → right arm → left arm) helps prevent lipodystrophy.

Lipodystrophy: Repeated injection in the same spot causes changes to the subcutaneous fat tissue — either hardening (lipoatrophy) or thickening (lipohypertrophy). These changes alter drug absorption, making dosing inconsistent. Site rotation prevents this.

Step-by-step technique

Pre-injection:

1. Remove pen from refrigerator 15–30 minutes before injecting. Cold medication causes more discomfort. See GLP-1 pen storage and travel guide for temperature limits.
2. Check the medication window — the solution should be clear and colourless or faintly coloured, with no particles.
3. Check the dose window to confirm the correct dose is set (applicable to multi-dose pens like Ozempic).
4. Wash hands.

Injection:

1. Choose your injection site; clean with an alcohol swab if desired (not required but common practice). Allow to dry.
2. Pinch a fold of skin between thumb and forefinger — this lifts the subcutaneous fat layer above the muscle.
3. Hold the pen at a 90-degree angle to the skin fold (or 45 degrees for very thin patients with minimal subcutaneous fat).
4. Insert the needle in a swift, smooth motion.
5. Release the skin fold after needle insertion.
6. Depress the plunger (or activation button on autoinjectors) fully and hold for the time specified in your device's instructions (typically 5–10 seconds) to ensure complete delivery.
7. Withdraw the needle straight out. Do not rub the site.

Post-injection:

• Dispose of used needle in a sharps container (not in household waste)
• If bleeding occurs at the injection site, apply gentle pressure with a clean cotton ball — a small amount of bleeding or bruising is normal
• Record your injection (date, site used) to maintain rotation tracking

Common mistakes

Injecting too close to the navel: The periumbilical area has different tissue characteristics. The 2-inch exclusion zone is in the prescribing instructions specifically.

Not rotating sites: The most common cause of injection site reactions, lipohypertrophy, and inconsistent drug absorption.

Injecting cold medication: Temperature affects both comfort and absorption consistency. Room temperature before injecting.

Injecting through clothing: Autoinjector pens are designed for direct skin contact. Injecting through clothing risks contamination and inaccurate needle depth.

Sharing injection pens: Never share a GLP-1 pen with another person even if the needle is changed. There is a risk of blood contamination and infection transmission.

Injection site reactions

Minor redness, bruising, or small bumps at the injection site are common and typically resolve within a few days. Persistent large lumps, significant swelling, or severe redness warrant prescriber evaluation.

If you repeatedly notice reactions at specific sites, rotate to other anatomical areas and ensure the medication is at room temperature before injecting.

What to do about missing doses

Ozempic/Wegovy (weekly): If a dose is missed and the next scheduled dose is more than 2 days away, inject the missed dose as soon as possible. If the next scheduled dose is within 2 days, skip the missed dose and resume the regular weekly schedule. Do not inject two doses to make up for the missed one. For the full Wegovy dose escalation schedule, including how to restart after a longer gap, see the dedicated guide.

Mounjaro/Zepbound (weekly): Same approach — manufacturer guidance specifies a 2-day window for making up the missed dose.

Specific make-up guidance is in each drug's patient guide, available from the manufacturer's website and your pharmacist.