How semaglutide works
Semaglutide copies GLP-1, a hormone your gut makes after meals. It helps your pancreas release the right amount of insulin when blood sugar is high, slows how fast your stomach empties, and lowers appetite. MedlinePlus notes it helps manage diabetes and weight but does not make them go away; results depend on staying on it.
| Brand | Form | Main FDA-approved uses |
|---|---|---|
| Wegovy | Weekly injection or daily tablet | Weight reduction and maintenance; lowering the risk of heart attack, stroke and cardiovascular death in adults with heart disease and obesity or overweight; injection only: MASH, a fatty liver disease with moderate to advanced scarring |
| Ozempic | Weekly injection or daily pill | Type 2 diabetes |
| Rybelsus | Daily tablet | Type 2 diabetes |
Common side effects
| Side effect | Wegovy 2.4 mg injection | Placebo |
|---|---|---|
| Nausea | 44% | 16% |
| Diarrhea | 30% | 16% |
| Vomiting | 24% | 6% |
| Constipation | 24% | 11% |
| Abdominal pain | 20% | 10% |
Other common side effects on the label include headache, tiredness, indigestion and reflux, dizziness, bloating, burping, gas, gastroenteritis, hair loss and skin sensitivity or tingling (dysesthesia). People with type 2 diabetes can also get low blood sugar, mainly when semaglutide is combined with insulin or a sulfonylurea.
In the trials, 6.8% of people on Wegovy stopped because of side effects, compared with 3.2% on placebo. Nausea, vomiting and diarrhea were the most common reasons.
Serious side effects and warnings
- Thyroid tumors (boxed warning). Semaglutide caused thyroid C-cell tumors in rodents. It isn't known whether it does in people. It isn't used by anyone with a personal or family history of medullary thyroid cancer or MEN 2.
- Pancreatitis, which can cause severe upper stomach pain that spreads to the back.
- Gallbladder problems, including gallstones.
- Kidney injury from dehydration after vomiting or diarrhea.
- Severe stomach and intestinal reactions; not recommended for people with severe gastroparesis.
- Faster heart rate. Your clinician may check it at visits.
- Diabetic eye disease can worsen in people with type 2 diabetes and a history of diabetic retinopathy.
- Serious allergic reactions, and aspiration during anesthesia, so tell every clinician you take it before surgery or sedation.
Semaglutide also slows the absorption of some pills, so your clinician may monitor medicines that need close dosing. Wegovy shouldn't be combined with any other semaglutide product or GLP-1 drug.
Get medical care right away for ongoing pain in the upper or middle stomach, with or without vomiting; swelling of the face, mouth or throat, a rash with dizziness, or trouble breathing or swallowing; yellow skin or eyes, fever or clay-colored stools; much less urine or swollen legs; vision changes; a fast, pounding heartbeat; or a neck lump, hoarseness or shortness of breath.
Making side effects easier
- Eat smaller meals and stop when you feel full.
- Go easy on fatty, fried, spicy and very sugary foods, which tend to worsen nausea.
- Sip fluids through the day. Dehydration worsens constipation and raises kidney risk.
- Tell your clinician if side effects are hard to live with. Slowing the dose increase is common. Your clinician decides the dose.
More food tips are in what to eat on a GLP-1. Planning a pregnancy or wondering about drinks? See semaglutide and alcohol, which also covers pregnancy and breastfeeding.
Through Gabriel, a licensed clinician reviews every prescription request and decides.
Common questions
What are the worst side effects of semaglutide?
The most serious listed risks are pancreatitis, gallbladder disease, kidney injury from dehydration, severe allergic reactions and a possible thyroid tumor risk seen in rodents. They are much less common than stomach side effects.
Do semaglutide side effects go away?
For many people, nausea and other stomach effects are worst when starting or raising the dose and improve after. If they don't, talk with your clinician rather than changing the dose yourself.
Are Ozempic and Wegovy side effects the same?
Both contain semaglutide and share the same main side effects and warnings. They are approved for different uses and come in different doses.
Can semaglutide cause low blood sugar?
The label warns that the risk rises when it's combined with insulin or a sulfonylurea, and those doses may need lowering. Signs include shakiness, sweating, hunger, confusion and a fast heartbeat.
How does semaglutide make you lose weight?
It slows stomach emptying and acts on appetite signals so you feel full sooner and eat less. It's approved for weight loss as Wegovy, used with a reduced-calorie diet and more activity.
Sources
- Wegovy (semaglutide) prescribing information, revised 06/2026 Novo Nordisk
- Semaglutide Injection MedlinePlus
- Semaglutide (Ozempic): How It Works and Side Effects Cleveland Clinic
- GLP-1 Agonists: What They Are, How They Work and Side Effects Cleveland Clinic
- How To Manage the Digestive Side Effects of GLP-1 Medications Cleveland Clinic
This guide is general information, not medical advice. It does not replace a visit with a licensed clinician. Gabriel membership is not health insurance.