Weight Loss Injections: Understanding Sites, Rotation, and Your Weekly Routine

Both Mounjaro and Wegovy are once-weekly injectable medicines. The three areas commonly used for subcutaneous injection are the abdomen (stomach area), the front of the thigh, and the upper arm. Your prescriber or doctor, along with the patient information leaflet that comes with your pen, will confirm the exact sites suitable for you.

Why rotation matters

Injecting into the same spot repeatedly can cause changes to the tissue under the skin — a condition sometimes called lipohypertrophy — which may affect how the medicine is absorbed. Rotating sites with each dose helps keep the skin in good condition and supports consistent delivery. A simple rule many people follow is to move to a different area each week, or at least to a different spot within the same area, leaving enough distance from the previous injection point.

Choosing a site

Each site has practical pros and cons. The abdomen is often the easiest to reach and to pinch a fold of skin; the thigh is accessible when sitting; the upper arm requires a little more care to use comfortably without assistance. There is no universally 'best' site — your prescriber or doctor is the right person to advise on what works for your individual circumstances.

For a closer look at using Mounjaro specifically, see how Mounjaro injections work and what to expect, or explore the broader picture of weekly injection routines for weight loss. If you were originally prescribed a GLP-1 medicine for blood sugar management and are now also using it for weight, the page on diabetes injections and weight loss covers how these medicines overlap.

After the injection

It is common to notice mild redness, itching, or tenderness at the injection site shortly after administering the dose. These reactions are generally short-lived. If a reaction is severe, spreads, or does not settle within a day or two, contact your healthcare professional. Side effects experienced after an injection — including any gastrointestinal symptoms — can be worth noting down with the date and which site you used, as patterns sometimes emerge over time.

Remembering which site you used last week — and logging each dose reliably — is exactly the kind of detail that is easy to lose track of across a long treatment journey. GLP Trackr's injection-site tracking feature lets you record the site used for each dose, and the app uses that history to suggest your next rotation automatically, so you never have to try to remember.

Alongside site tracking, the dose logging feature captures the date, time, and dose strength of every injection in one place. If you ever need to confirm when your last dose was — whether for your own peace of mind or to discuss with your prescriber — it is all there at a glance. Dose reminders can also be set so a weekly injection is never quietly forgotten.

GLP Trackr is available on the App Store and Google Play. Try it free for 7 days and see how straightforward keeping track of your injection routine can be — no fee required to get started.

For a fuller guide covering everything from how these medicines work to managing common experiences along the way, visit the weight loss injections hub.

Any concerns about your injection technique, site reactions, or how your medicine is working should always be taken to your prescriber or doctor — they know your full medical history and are best placed to advise. GLP Trackr records your journey; it is not a substitute for professional guidance.