Semaglutide Injection: How the Medication Is Administered

Where does the injection go?

Semaglutide is a subcutaneous injection, which means into the fatty layer under the skin rather than into muscle or a vein [1][2]. The Ozempic label names three sites — the abdomen, the thigh and the upper arm — and tells patients to use a different injection site each week when injecting in the same body region [1]. Wegovy's label pharmacokinetics found similar semaglutide exposure at the abdomen, thigh and upper arm [2].

Injection site reactions were reported in 1.4% of people taking Wegovy 2.4 mg versus 1% on placebo in the pooled weight-management trials [2]. The Ozempic label says to inspect the pen before use: the solution should be clear and colorless, and the pen should not be used if particulate matter or coloration is visible [1]. Both labels state that a pen must never be shared between patients, even if the needle is changed [1][2].

What is the starting dose, and how fast does it climb?

The Wegovy label escalates in four-week steps: 0.25 mg weekly for weeks 1 to 4, 0.5 mg for weeks 5 to 8, 1 mg for weeks 9 to 12, 1.7 mg for weeks 13 to 16, then maintenance from week 17 [2]. For weight reduction, the recommended Wegovy maintenance dose is 2.4 mg weekly, with 1.7 mg weekly as an alternative [2]. Adults who tolerate 2.4 mg for at least 4 weeks and still need more weight loss may go to a maximum of 7.2 mg weekly; the pediatric maximum is 2.4 mg [2].

Ozempic, which is approved for type 2 diabetes and has no weight-loss indication, runs on its own ladder: 0.25 mg once weekly for 4 weeks — the label calls this a starting dose and not a maintenance dose — then 0.5 mg, with maintenance at 0.5, 1 or 2 mg and each increase made only after at least 4 weeks on the current dose [1]. The maximum is 2 mg weekly [1].

Nausea, vomiting and diarrhea were reported most often during Ozempic dose escalation [1]. In the Ozempic label's pooled placebo-controlled trials, nausea was reported by 6.1% of placebo patients, 15.8% of those on 0.5 mg and 20.3% of those on 1 mg, and any GI reaction by 15.3%, 32.7% and 36.4% respectively [1]. In pooled Wegovy 2.4 mg weight-management trials involving adults with obesity or overweight, nausea occurred in 44% versus 16% on placebo, vomiting 24% versus 6%, diarrhea 30% versus 16% and constipation 24% versus 11%; 6.8% on Wegovy stopped for adverse reactions versus 3.2% on placebo [2].

At the 7.2 mg dose, two 72-week trials in adults with obesity reported nausea in 39% on 7.2 mg, 35% on 2.4 mg and 13% on placebo, and dysesthesia — altered skin sensation such as burning or pain from touch — in 22%, 6% and 0% [2].

What happens if a weekly dose is missed?

The two labels use different rules. For Wegovy, the label says a missed dose is given if the next scheduled dose is more than 2 days away, and after 2 or more consecutive missed doses the schedule restarts from a lower dose [2]. For Ozempic, the label says a missed dose is given within 5 days of the scheduled time; otherwise it is skipped, and the day of the week can be changed as long as the two doses are more than 48 hours apart [1].

What does the label say to watch for?

Every semaglutide label carries a boxed warning on thyroid C-cell tumors [3][1][2]. In rodents, semaglutide caused dose- and treatment-duration-dependent thyroid C-cell tumors at clinically relevant exposures, and whether it causes them in humans is unknown [3][1][2]. It is contraindicated in people with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2, and the label says to counsel patients on symptoms such as a neck mass, trouble swallowing, shortness of breath and persistent hoarseness [3][1][2].

The Wegovy label warns about acute pancreatitis and instructs discontinuation if pancreatitis is suspected [2]. It also lists acute gallbladder disease (cholelithiasis in 1.6% versus 0.7% on placebo and cholecystitis in 0.6% versus 0.2% in the adult injection trials), hypoglycemia when combined with insulin or a sulfonylurea, acute kidney injury from volume depletion, severe GI reactions (4.1% versus 0.9%), hypersensitivity reactions, monitoring for diabetic retinopathy progression, a rise in heart rate (mean 1 to 4 beats per minute, with a rise of 20 beats per minute or more in 26% versus 16%), and pulmonary aspiration during general anesthesia or deep sedation [2]. The Ozempic label lists the same items except the heart-rate warning, and its pen must also never be shared [1].

The half-life is about 1 week, and semaglutide stays in the body for roughly 5 to 7 weeks after the last 2.4 mg or 7.2 mg injection or 25 mg tablet [2]. Both labels say to stop at least 2 months before a planned pregnancy [1][2].

What about compounded semaglutide injections?

Compounded drugs are not FDA approved and are not reviewed for safety, effectiveness or quality before marketing [4]. As of 2026-05-31, FDA had received 990 adverse event reports for compounded semaglutide and says this likely undercounts; the agency also reports dosing errors with compounded injectable semaglutide, including patients measuring the wrong dose, clinicians miscalculating doses, and doses above the labeled amount [4]. Semaglutide sodium and semaglutide acetate salts are different active ingredients from the approved drug, with no lawful basis for compounding that FDA is aware of [4].

For multi-dose vials, FDA recommends discarding the vial 28 days after first use even if medication remains, using a new sterile needle and syringe for every dose, and not using an injectable GLP-1 drug that arrives warm or with insufficient refrigeration [4].

What did the schedule produce in a trial?

STEP 1 enrolled 1,961 adults with a BMI of 30 or higher, or 27 or higher with a weight-related condition, and no diabetes [5]. Over 68 weeks, semaglutide 2.4 mg weekly plus lifestyle intervention produced a mean weight change of -14.9% versus -2.4% on placebo, a difference of -12.4 percentage points; at least 15% weight loss occurred in 50.5% versus 4.9%, and 4.5% versus 0.8% discontinued for GI events [5].