Clinically reviewed by Dr. Ponlawat Pitsuwan, Physician, Doctor Bangkok. Last reviewed: July 2026
Ozempic and Mounjaro pens are injected once weekly under the skin of the abdomen, thigh or upper arm. Wash your hands, choose and rotate the site, inject as your pen instructs, and dispose of needles safely. Always follow the specific instructions your doctor and the pen leaflet give you.
Most people are nervous about their first injection and relieved by how simple it turns out to be. These pens are designed for self-use, and once you have done it once or twice it becomes routine. This guide walks through the general steps so you know what to expect.
Two important caveats first. Pens differ, so the leaflet that comes with your specific device always takes priority over any general guide. And we teach you the technique in person at the clinic before you start at home, so you are never left guessing.
Before you inject
Wash your hands. Check the pen is the right medicine and dose, and that the liquid looks clear as described in the leaflet. Let a refrigerated pen come closer to room temperature if your instructions advise it, as cold injections can sting more. Attach a new needle if your pen uses detachable needles.
Where to inject: choosing a site
These medicines are injected subcutaneously, meaning into the fatty layer just under the skin. The usual sites are the abdomen (avoiding the area right around the navel), the front of the thighs, and the back of the upper arms. Any of these is fine; the key is to rotate.
Why rotation matters
Injecting into the same spot repeatedly can cause lumps or skin changes that affect how the medicine is absorbed. Move to a different area each week and avoid skin that is bruised, tender, hardened or broken.
Step-by-step technique
Clean the chosen area and let it dry. Following your pen’s instructions, press the pen against the skin and deliver the dose, holding it in place for the number of seconds the leaflet specifies so the full dose goes in. Remove the pen, and if there is a small drop of blood, press gently with a clean tissue. Do not rub the site. Dispose of the needle in a proper sharps container, never in household rubbish.
Timing and missed doses
These are weekly injections, and picking a consistent day helps you remember. If you miss a dose, the correct action depends on how many days have passed and your specific medicine, so follow your leaflet or ask us rather than doubling up. Your doctor will advise how to handle missed doses safely.
Storing your pen
Storage matters, especially in Bangkok’s heat. Unused pens are usually kept refrigerated, and there are limits on how long a pen can be kept at room temperature once in use. Follow the exact storage instructions on your pen and never leave it in a hot car or in direct sun.
When to call your doctor
Contact us if a site becomes increasingly red, swollen, warm or painful over days, if you have an allergic reaction, or if you are unsure whether a dose went in correctly. And separate from injection technique, seek prompt care for severe abdominal pain, persistent vomiting or dehydration, which our guide to GLP-1 side effects covers. Our 24/7 clinic means help is available whenever you need it.
Starting injections and want to feel confident? We teach the technique in person before you self-inject at home. See our overview of weight-loss injections in Bangkok or contact the clinic.
Frequently asked questions
Does the injection hurt?
Most people find it causes only a minor pinch, as the needles are very fine. Letting a cold pen warm slightly and rotating sites both help.
What time of day should I inject?
Any time of day is generally fine; consistency of the weekly day matters more. Choose a day you will remember.
Can I inject through clothing?
No. Inject into clean, bare skin so you can see the site and keep it hygienic.
What if I see a little blood or bruising?
A small drop of blood or minor bruise is common and harmless. Press gently with a tissue and avoid that spot next time.
How do I dispose of used needles in Bangkok?
Use a proper sharps container, never household bins. We can advise on safe disposal and where to return full containers.
Dr. Ponlawat Pitsuwan
Physician, Doctor Bangkok
Dr. Ponlawat is a physician at Doctor Bangkok, a private medical clinic in central Bangkok. He teaches patients safe self-injection technique as part of their weight-management programme.
Dr. Ponlawat Pitsuwan is a physician at Doctor Bangkok, a private clinic in central Bangkok. He sees expats, residents, and medical tourists for general medicine, wellness consultations, and IV therapy. His focus is straightforward, evidence-based care delivered in plain language.