Common mistakes to avoid
- Don't inject into muscle: The injection should go into the fat layer just under the skin (subcutaneous), not into muscle. Pinch the skin and inject at 90 degrees.
- Don't reuse pens: Mounjaro pens are single-use. Each pen contains one dose. Discard after injection.
- Don't inject into bruised, scarred, or irritated skin: Choose a clean, healthy area.
- Don't store with the cap off: Light exposure can degrade the medication.
- Don't freeze: If accidentally frozen, discard the pen even if it thaws. Freezing can damage the protein structure of the medication.
Injection site rotation
Rotate injection sites each week to prevent lipodystrophy (lumps or indentations under the skin from repeated injection in the same spot). A simple rotation: abdomen left side → abdomen right side → left thigh → right thigh → repeat. Keep at least 2cm between injection sites.
Dealing with needle anxiety
If you're nervous about self-injection, know that you're not alone — and that it's almost always much easier than expected. The Mounjaro pen uses a hidden needle (you don't see it), and most patients describe the sensation as a slight pinch that's over in seconds. After 2–3 injections, the vast majority of patients describe it as completely routine.
If anxiety persists, ask your pharmacist for a demonstration on your first injection, or ask a partner/family member to help.