Semaglutide Side Effects: What to Expect in a Clinic Program

Gastrointestinal effects dominate the data.

In the Wegovy 2.4 mg injection weight trials — 2,116 adults on semaglutide versus 1,261 on placebo — the label's side-effect table reads as follows.

Fatigue is on the table too, at 11% versus 5% on placebo, which is where the "does semaglutide make you tired" question lands: tiredness is a labeled effect, well behind the gastrointestinal list.

Hair loss was reported by 3% of semaglutide patients versus 1% on placebo.

Across the adult weight trials as a whole, 73% of patients on Wegovy injection reported a gastrointestinal side effect versus 47% on placebo.

These are trial averages, not a prediction for any one patient — someone following the label's titration spends weeks at each lower dose before reaching the 2.4 mg maintenance dose.

In STEP 1, nausea and diarrhea were the most common adverse events, typically transient and mild-to-moderate in severity and subsiding with time; 4.5% of semaglutide patients versus 0.8% on placebo stopped because of gastrointestinal events.

The label's own explanation is dose escalation: gastrointestinal reactions were most frequently reported while doses stepped up, which is why the Wegovy label raises the dose slowly over 16 weeks before maintenance.

• Weeks 1 to 4: 0.25 mg once weekly
• Weeks 5 to 8: 0.5 mg once weekly
• Weeks 9 to 12: 1 mg once weekly
• Weeks 13 to 16: 1.7 mg once weekly
• From week 17: 2.4 mg once weekly (the recommended maintenance dose) or 1.7 mg

That schedule is also the honest answer to "how long do semaglutide side effects last": STEP 1 described nausea and diarrhea, its most common effects, as typically transient and subsiding with time, and the label says GI reactions were most frequently reported during dose escalation — but we found no label or trial figure for how many days an individual bout of nausea or diarrhea lasts.

When a step does not agree with you, that is precisely what the prescriber titrating your dose is there to hear about.

Some patients decide the trade is not worth it: in the weight trials, 6.8% of patients on Wegovy 2.4 mg versus 3.2% on placebo permanently stopped because of adverse reactions, most commonly nausea, vomiting and diarrhea.

Serious risks sit in two places on the Wegovy label: the boxed warning at the top, and the warnings list that covers the gallbladder, the pancreas and several other systems.

Gallstones (cholelithiasis) were reported by 1.6% of Wegovy injection patients versus 0.7% on placebo, and acute pancreatitis was confirmed in 4 Wegovy-treated patients — 0.2 cases per 100 patient-years — versus 1 patient on placebo.

The warnings list also includes acute kidney injury from dehydration, severe gastrointestinal reactions, hypersensitivity reactions, complications of diabetic retinopathy, an increase in heart rate, and pulmonary aspiration under anesthesia.

These are the label's own warnings — the documented risks behind the "long-term side effects" question.

Compounded semaglutide is not held to the standard the branded trials were: compounded drugs are not FDA-approved, FDA does not review them for safety, effectiveness or quality before they are marketed, and the agency says compounded drugs should be used only in patients whose medical needs cannot be met by an FDA-approved drug.

The legal back story is its own topic — see compounded GLP-1s.

FDA's tracking puts numbers on the record: as of May 31, 2026, the agency had received 990 adverse-event reports associated with compounded semaglutide and more than 730 for compounded tirzepatide.

FDA notes the counts are likely underreported, because 503A pharmacies are not required to report adverse events, and that causation cannot always be determined — report counts are not incidence rates.

The documented problems are specific.

FDA's July 2024 alert describes compounded semaglutide dosing errors, some needing hospitalization, from patients drawing up the wrong amount from multi-dose vials — 5 to 20 times the intended dose — and from clinicians miscalculating milligram-to-"units" conversions by 5 to 10 times the intended dose.

The agency has also received adverse-event reports linked to compounded semaglutide or tirzepatide prescribed above label doses: larger doses, more frequent doses, or faster titration, some serious.

Start with the effects that actually end treatment in the data: nausea, vomiting and diarrhea were the most common reasons patients in the weight trials permanently stopped.

If gastrointestinal effects are severe — the label separately warns of severe gastrointestinal reactions and of acute kidney injury from dehydration — that is a prescriber conversation, not something to manage alone.

Pregnancy has its own label instructions: stop Wegovy when pregnancy is recognized, and discontinue at least 2 months before a planned pregnancy because of semaglutide's long half-life.

Breastfeeding is not recommended while taking the Wegovy tablets.

FDA's alert on compounded dosing errors lists severe nausea, vomiting and low blood sugar as semaglutide overdose symptoms that may need prolonged care, because the drug's half-life is about one week.

If you believe you have taken more than the intended dose — the drawing errors FDA documented ran from 5 to 20 times the intended dose, and the conversion errors from 5 to 10 times — that belongs with the prescribing clinic immediately, and with emergency care for severe symptoms.

The label builds monitoring into the treatment's structure.

The 16-week titration exists because gastrointestinal effects concentrate during dose escalation, and it creates a natural checkpoint every 4 weeks, when the dose is due to step up.

Screening is the other half.

The boxed warning's contraindication — a personal or family history of medullary thyroid carcinoma or MEN 2 — and pregnancy plans are exactly the history a prescriber needs before the first prescription, not after.

Between visits, these are the questions worth putting to any program:

A program that can answer all three without hedging has done the work the label's structure assumes.

A legitimate program starts with a prescription: Wegovy is prescription-only, filled at a state-licensed pharmacy, on a valid prescription from a licensed prescriber.

Which licenses can start it — a physician, a nurse practitioner, a PA, or someone working under supervision — is set by state law rather than by the FDA label, so it is worth reading who can prescribe GLP-1s before you book anywhere.

FDA's red flags for GLP-1 offers double as a screening checklist for any clinic or telehealth program: claims that a compounded drug is the same as an FDA-approved drug; deep discounts that seem too good to be true; no screening and prescription by a licensed doctor; no doctor available for questions; label spelling errors or a wrong pharmacy address; or a pharmacy name you suspect is fraudulent.

For the drug itself — approved uses, trial results and what the branded products cost — start with the semaglutide guide.