GLP-1 medications like Ozempic, Wegovy, Mounjaro, and Zepbound are subcutaneous injections — they go just under the skin into the fat layer, not into muscle. Three body areas are FDA-approved: abdomen, front-outer thigh, and back of the upper arm. Absorption is similar but not identical — bioavailability is roughly 12% lower from the thigh than the abdomen, though not clinically meaningful for most patients. The real variable is rotation: as many as two-thirds of patients who inject regularly develop lipohypertrophy (palpable fatty lumps) at some point, which slows absorption and dents the consistency of dosing.
Direct answer: Inject subcutaneously into the abdomen (at least 2 inches / two finger-widths from the belly button), the front or outer-front of the thigh between knee and hip, or the back of the upper arm. Bioavailability from the thigh is about 12% lower than the abdomen — usually not clinically meaningful. Rotate every dose — either between body areas or shift at least 1 inch within the same area, keeping any single spot a 4–6 week break between reuses. Pinch a fold of skin, insert at 90° (or 45° if very lean), hold 5 seconds, withdraw, don't rub, dispose in a sharps container.
The Three FDA-Approved Sites
| Site | Pros | Cons | Best for |
|---|---|---|---|
| Abdomen | Largest area; easiest to self-inject; consistent fat layer; slightly faster absorption | Lumps appear faster if not rotated | Most people, weekly dosing |
| Thigh (front-outer) | Easy to see; ample subQ fat in most adults; ~12% slower absorption | Tighter skin can sting more; harder for very lean people | Backup/second weekly site |
| Upper arm (back, outer) | Discreet | Hard to self-inject solo — typically needs a partner | When abdomen and thigh need a break |
Abdomen
The default for most people on a weekly GLP-1:
- Stay at least 2 inches (about two finger-widths) from the belly button
- Use a roughly half-moon shape around the navel, excluding scars, stretch marks, and skin folds
- Skip the immediate waistband area where pants press
Thigh
- Use the front or outer front of the thigh, never the inner thigh (vessels and nerves)
- Halfway between hip and knee
- Pinch generously — thigh skin is tighter than abdominal skin
- Absorption is ~12% lower than abdomen but rarely clinically meaningful
Upper Arm
- The fleshy outer back of the upper arm, halfway between shoulder and elbow
- Hard to do solo; ask a partner or skip this site if injecting alone
- Lean arms may not have enough subcutaneous fat — switch to a shorter needle or 45° angle
Why Rotation Matters
Injecting repeatedly in the exact same spot leads to:
- Lipohypertrophy — palpable lumps of thickened fatty tissue, which can "reduce or limit absorption, and may remain for weeks or months." Up to two-thirds of regular injectors develop this at some point.
- Lipoatrophy — pits or depressions where fat thins out
- Slowed or erratic absorption through changed tissue, leading to inconsistent dose response
- Itching, redness, bruising that lingers longer than usual
The rule of thumb: keep any specific spot on a 4–6 week break before reusing it.
Two Rotation Patterns That Work
Pattern 1 — Rotate Between Areas
Easiest to remember:
- Week 1: abdomen (left side)
- Week 2: thigh (left)
- Week 3: thigh (right)
- Week 4: abdomen (right side)
- Week 5: upper arm (if available) or back to abdomen
Pattern 2 — Stay in One Area, Shift Position
Pick the abdomen (or thigh), divide mentally into a 2x2 or clock pattern, and move 1+ inch each week:
- Week 1: upper left abdomen
- Week 2: upper right abdomen
- Week 3: lower right abdomen
- Week 4: lower left abdomen
- Week 5: cycle back, but offset slightly
Either approach works. Consistency matters more than the specific pattern.
Technique Step-by-Step
- Wash hands.
- Take the pen out of the fridge 15–30 minutes before — cold injection stings more.
- Choose a site and rotate from last week.
- Clean the skin with an alcohol swab; let it dry. Wet alcohol stings.
- Inspect the medication — clear, colorless, no particles. If cloudy, do not inject.
- Prepare the pen or syringe per the device instructions; remove the cap.
- Pinch a 1–2 inch fold of skin between thumb and index finger.
- Insert at 90° (straight in) for adults of normal weight; consider 45° if very lean.
- Press the button or plunger slowly all the way down.
- Hold for 5–10 seconds to ensure full dose delivery (per pen instructions).
- Withdraw the needle straight out.
- Don't rub — a gentle press with gauze is fine.
- Dispose of the needle in a sharps container, never a regular trash can.
What If Something Goes Wrong
| Issue | What it means | What to do |
|---|---|---|
| Slight bleeding | Nicked a small capillary | Press gently 1 minute. No further action needed. |
| Larger bruise | Hit a deeper vessel | Apply cold pack; resolves in days. |
| Sharp pain into muscle | Needle went too deep | Continue the dose; effect is still therapeutic. Switch to 45° next time. |
| Drop of medication leaks out | Needle came out too fast or pinch released early | Do not redose; small loss does not change response meaningfully. |
| Lump that lasts weeks | Lipohypertrophy | Rotate aggressively away from that spot for 4–8 weeks. |
| Persistent redness > 48 hours | Possible infection or allergic reaction | Contact prescriber. |
Common Mistakes
- Injecting cold medication. Take the pen out of the fridge 15–30 minutes early.
- Reusing needles. Use a new needle every dose. Reusing dulls the tip and increases lump risk.
- Skipping the hold time. Pulling the needle out too fast wastes drug.
- Injecting through clothing. Don't. Skin needs to be clean and visible.
- Using the same spot every time. Even if it feels easier, lipohypertrophy will catch up.
- Aspirating before injection. Not necessary with short subcutaneous needles.
- Injecting into a stretch mark or scar. Absorption is unreliable.
Special Cases
- Pregnant abdomen — switch to thighs or upper arms during pregnancy (though most GLP-1s are contraindicated in pregnancy regardless).
- Visible bruising or skin condition in your usual area — pick a different site that week.
- Recent abdominal surgery — wait until the surgeon clears the area; use thigh in the meantime.
- Very lean body — pinch carefully, consider a 4–6 mm needle, and use a 45° angle to stay in subcutaneous fat.
Storage Right Before Injection
- Refrigerated until first use: standard for sealed pens
- Room temperature is OK for in-use pens for 28–56 days depending on the product
- Take pen out 15–30 minutes before injecting to reduce stinging
- Never inject frozen medication — discard and contact pharmacy
Frequently Asked Questions
Where is the best place to inject a GLP-1? Any of the three FDA-approved sites: abdomen (at least 2 inches from navel), front of thigh, or back of upper arm. Most people choose abdomen because it's easiest.
Does the injection site affect how the drug works? Trial data shows bioavailability from the thigh is about 12% lower than the abdomen, but the difference is rarely clinically meaningful for routine dosing.
Should I inject in muscle or fat? Always subcutaneous fat. GLP-1 medications are not approved or studied for intramuscular injection.
How often should I rotate sites? Every dose. Keep any specific spot on a 4–6 week break before reusing it. Up to two-thirds of patients develop lipohypertrophy without good rotation.
Is bleeding after injection normal? A drop is normal. Larger bruises resolve on their own. Persistent redness over 48 hours warrants a call to the prescriber.
Can I inject myself in the upper arm? Technically yes, but it's awkward without help. Most people who use the arm have a partner administer it.
Does cold medication hurt more? Yes. Take the pen out of the fridge 15–30 minutes before injecting to reduce stinging.
Last reviewed: May 13, 2026
