Semaglutide side effects: how common they are, what helps, when to call

Most people on semaglutide get at least one stomach-related side effect. Most of it is mild to moderate, clusters around dose increases and passes. In the Wegovy label, 73% of people had a gastrointestinal reaction versus 47% on placebo. The figures below come from the FDA labels and pool three placebo-controlled weight trials: 2,116 adults on Wegovy 2.4 mg and 1,261 on placebo, for up to 68 weeks.

6.8% of people on Wegovy stopped because of a side effect, against 3.2% on placebo. The leading reasons were nausea (1.8% versus 0.2%), vomiting (1.2% versus 0%) and diarrhea (0.7% versus 0.1%). Severe gastrointestinal reactions were reported in 4.1% versus 0.9%. In the larger SELECT heart trial, which ran a median of more than 3 years, 16% on Wegovy and 8% on placebo stopped because of an adverse event.

When do semaglutide side effects start, and how long do they last?

Stomach side effects usually start during the climb to a full dose and fade within days to weeks. A pooled analysis of the STEP 1, 2 and 3 trials found these events were transient and came most often during or shortly after a dose increase. 98.1% were mild to moderate, and 99.5% were not serious. Each step up can bring a fresh round, so feeling fine on one dose does not guarantee the next will go the same way.

An expert consensus on GLP-1 drugs as a class gives a rough timeline. It was funded by Novo Nordisk, so read it as a practical guide and not an independent finding.

One question people ask is whether side effects mean the drug is working. They do not seem to. In the same pooled STEP analysis, people lost similar amounts of weight with or without stomach side effects, so a quiet stomach is no sign that the dose is failing.

Why does semaglutide upset your stomach?

Semaglutide slows stomach emptying and acts on the brain’s appetite centers. Both effects build as blood levels rise, which is why each step up the semaglutide dosage chart can bring symptoms. The labels build the schedule around this: the Wegovy label says to follow it “to reduce the risk of gastrointestinal adverse reactions.”

What helps with semaglutide nausea and constipation?

Eating less at a sitting, eating slowly and stopping when you feel full are the first steps the consensus recommends. The plan itself belongs to your prescriber, and the items below come from either the label or that consensus.

From the label and Medication Guide:

• Slower escalation. The Wegovy label says that if a dose is not tolerated, the prescriber can “consider delaying dosage escalation for 4 weeks.” Maintenance can also be 1.7 mg in place of 2.4 mg.
• Fluids. The Medication Guide says “it is important for you to drink fluids to help reduce your chance of dehydration,” because vomiting and diarrhea can lead to kidney problems.
• Do not double up. An overdose can cause severe nausea, severe vomiting and severe low blood sugar. The missed-dose rules exist for this reason.
• Rotate injection sites. Change the site with each injection, across the abdomen, thigh or upper arm. The injection sites guide shows how.
• For the pill, follow the morning routine. Empty stomach, no more than 4 ounces of plain water, then at least 30 minutes before food, drinks or other oral medicines. If the 25 mg tablet is not tolerated, the label lets the prescriber consider switching to the 1.7 mg injection.

From the expert consensus:

• For any stomach symptom: eat slowly, eat smaller portions more often, eat only when hungry, stop when full, choose bland low-fat food, and avoid lying down after a meal.
• For nausea: crackers, apples, mint or ginger may help, and strong smells are worth avoiding.
• For vomiting: be careful about hydration. If it persists, drink 30 to 60 minutes before or after meals and not during them.
• For diarrhea: drink plenty of fluids. Cut back for now on dairy, coffee, alcohol, soft drinks, sugar alcohols such as sorbitol, and high-fiber foods.
• For constipation: get enough fiber, drink water or other sugar-free liquids, and move more. A stool softener may be an option; ask first.
• For reflux: fatty, fried or processed foods, alcohol and carbonated drinks are common triggers.

If symptoms keep going despite these steps, the consensus says to tell your clinician as soon as possible, and a pause or dose change may be considered.

Wegovy HD (7.2 mg): what changes at the higher dose

The 7.2 mg dose was tested in two 72-week trials with 1,311 people on 7.2 mg, 304 on 2.4 mg and 303 on placebo.

5% stopped because of side effects on 7.2 mg, 5% on 2.4 mg and 2% on placebo.

Dysesthesia is the new signal: sensitivity, tingling, pain or burning of the skin. The label says it rose with dose and blood levels. Among 288 people who had it on 7.2 mg, 2% stopped the drug, 8% paused it and 23% had the dose reduced. Most of those recovered, and recovery was faster when the dose was changed. 18% had not recovered by the end of the trial. Of 38 people who recovered and went back up to 7.2 mg, 17 had it again. The FDA said in its approval announcement that it is investigating this reaction further.

Wegovy pill side effects

The label’s 64-week pill trial included 204 adults on Wegovy 25 mg tablets. The label says the types and frequency of common side effects were “similar to” the injection table above, and it does not publish a separate table. What it does report:

• 6.9% stopped because of a side effect, versus 5.9% on placebo; gastrointestinal reasons accounted for 3.4% versus 2%.
• Severe gastrointestinal reactions: 2% versus 0%.
• Gallstones: 2.5% versus 1%.
• Dysesthesia: 5% versus none on placebo.

Ozempic side effects in the diabetes trials

The Ozempic label pools placebo-controlled trials in adults with type 2 diabetes, at lower doses than Wegovy.

Stopping because of gastrointestinal effects was 3.1% on 0.5 mg and 3.8% on 1 mg, against 0.4% on placebo. In a 40-week trial comparing doses, gastrointestinal reactions were reported by 34% on 2 mg and 30.8% on 1 mg. The molecule is identical to Wegovy; the doses and trial populations were not.

Serious side effects and the boxed warning

Each of these is uncommon, and each is a reason not to wait out a specific symptom. The list follows Section 5 of the Wegovy label, revised June 2026.

• Thyroid C-cell tumors (boxed warning). Semaglutide caused these tumors in mice and rats; whether it does in humans is unknown. Contraindicated with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2. Report a neck lump, trouble swallowing, shortness of breath or lasting hoarseness.
• Acute pancreatitis. Confirmed in 4 people on Wegovy (0.2 cases per 100 patient-years) versus 1 on placebo in the adult weight trials. The symptom is persistent, severe stomach pain, sometimes into the back. The label says to stop the drug if pancreatitis is suspected. Postmarketing reports include necrotizing pancreatitis, sometimes fatal.
• Acute gallbladder disease. Gallstones in 1.6% on Wegovy injection versus 0.7% on placebo, and cholecystitis (gallbladder inflammation) in 0.6% versus 0.2%. In adolescents, gallstones reached 3.8%. The label says the excess held “even after accounting for the degree of weight loss.”
• Low blood sugar. In the weight trial of adults with type 2 diabetes, glucose below 54 mg/dL occurred in 6.2% on Wegovy versus 2.5% on placebo, and the risk rose with a sulfonylurea. With insulin or a sulfonylurea, the label says prescribers should consider lowering those doses when starting.
• Acute kidney injury from dehydration. Seen in 7 people on Wegovy versus 4 on placebo in the weight trials, some after vomiting or diarrhea, and in postmarketing reports, some needing dialysis.
• Severe gastrointestinal reactions. Wegovy is not recommended in people with severe gastroparesis (a stomach that empties very slowly). Postmarketing reports include ileus, intestinal obstruction, and severe constipation including fecal impaction.
• Serious allergic reactions. Anaphylaxis and angioedema (swelling of the face, lips or throat) have been reported.
• Diabetic retinopathy complications. In a 2-year trial of semaglutide injection, these occurred in 3% versus 1.8% on placebo, and in 8.2% versus 5.2% among people who already had retinopathy. Fast improvement in blood sugar can temporarily worsen diabetic eye disease.
• Heart rate increase. Average resting heart rate rose 1 to 4 beats per minute. 26% of people on Wegovy had a rise of 20 or more beats per minute at some visit, versus 16% on placebo. The label says to stop the drug for a sustained increase at rest.
• Food entering the lungs under anesthesia. Because the stomach empties slowly, the label asks patients to tell every provider about Wegovy before a planned surgery or procedure.
• Never share a FlexTouch pen. Added in June 2026: the multi-dose pen must never pass between people, even with a new needle, because of the risk of blood-borne infection. The Ozempic label carries the same warning for its pens.

The label also reports, outside the warnings section: low blood pressure in 1.3% versus 0.4%, fainting in 0.8% versus 0.2%, appendicitis in 0.5% versus 0.2%, and, in the SELECT trial, more hip and pelvis fractures in women (1% versus 0.2%) and in people 75 and older (2.4% versus 0.6%). Hair loss ran 3.3% versus 1% on 2.4 mg (4% of women and 0.9% of men on the drug) and 5.8% on 7.2 mg (8.4% of women and 0.2% of men), and the label ties it to weight reduction.

One warning has gone the other way. The label’s recent changes mark “Suicidal Behavior and Ideation” as removed in January 2026. A new or worsening mood change still deserves a call, even though it is no longer a labeled warning.

Can semaglutide cause vision loss?

Very rarely, it may. In June 2025 the safety committee of the European Medicines Agency concluded that NAION (non-arteritic anterior ischemic optic neuropathy, a sudden loss of vision caused by reduced blood flow to the optic nerve) is a very rare side effect of semaglutide, affecting up to 1 in 10,000 people. In adults with type 2 diabetes, it cited studies suggesting about a two-fold higher risk, roughly one extra case per 10,000 person-years of treatment.

The US labels are different. We searched the Wegovy label (June 2026), the Ozempic injection label (May 2026) and the Rybelsus and Ozempic tablet label (January 2026), and none of them names NAION. They do warn about diabetic eye complications and tell people with type 2 diabetes to report vision changes. The European advice is to contact a doctor promptly if vision drops suddenly or worsens quickly, and to stop semaglutide if NAION is confirmed.

When to stop semaglutide and call

The Medication Guide uses “stop” or “call right away” for a short list. These are the manufacturer’s instructions, not this site’s.

If you take too much, the Medication Guide says to call your provider or Poison Help at 1-800-222-1222, or go to the nearest emergency room. You can report a side effect to the FDA at 1-800-FDA-1088.

Do the numbers apply to compounded semaglutide?

They do not, because compounded semaglutide was never in these trials. It comes in multi-dose vials, and the percentages above come from the FDA-approved products. As of May 31, 2026, the FDA had received 990 adverse event reports tied to compounded semaglutide, and says the true number is likely higher because many pharmacies are not required to report. It has documented overdoses of 5 to 20 times the intended dose when units on a syringe were confused with milligrams. The compounded semaglutide guide explains the units math. For the same rates on the other big drug, see semaglutide vs tirzepatide.

Who should not use semaglutide at all

The label’s contraindications are a personal or family history of medullary thyroid carcinoma, Multiple Endocrine Neoplasia syndrome type 2, and a prior serious allergic reaction to semaglutide or any ingredient. It should not be combined with another semaglutide product or another GLP-1 drug. The label advises stopping it at least 2 months before a planned pregnancy, and breastfeeding is not recommended on the tablets. Whether any of this applies to you is a decision to make with your prescriber.