Wegovy Side Effects
Comprehensive guide to Wegovy (semaglutide (injection)) side effects from the STEP-1 clinical trial. How they feel, how long they last, what to do, and when to call your prescriber.
Most important:Side effects are usually worst during dose escalation and improve as your body adjusts. If symptoms are severe or persistent, your prescriber can pause or slow your titration — don't suffer in silence.
Nausea
Timing
Most common during dose escalation (first 4–8 weeks). Usually resolves within 2 weeks of each dose increase.
Severity
Mild to moderate in most patients. Severe in 5–10%.
How to manage
- ✓Eat smaller, more frequent meals
- ✓Avoid greasy, fried, or spicy foods during titration
- ✓Stay hydrated — sip water rather than gulping
- ✓Try ginger tea or peppermint
- ✓Take dose in the evening so you sleep through peak
⚠ Call your prescriber if: Persistent vomiting >24 hours, signs of dehydration (dizziness, dark urine), or unable to keep liquids down.
Diarrhea
Timing
Often appears 2–4 weeks into treatment. Improves within 1–2 weeks.
Severity
Usually mild. Watery diarrhea more common than urgent.
How to manage
- ✓Eat low-FODMAP foods (banana, rice, applesauce, toast)
- ✓Avoid coffee, alcohol, and high-fat meals
- ✓Use OTC loperamide if approved by your prescriber
- ✓Replenish electrolytes (Pedialyte, oral rehydration solution)
⚠ Call your prescriber if: Bloody stools, fever, severe abdominal pain, or diarrhea lasting >48 hours.
Constipation
Timing
Develops 1–4 weeks in. Can persist throughout treatment for some patients.
Severity
Mild to moderate. Affects ~20% of patients.
How to manage
- ✓Increase fiber intake (start slow — too fast can worsen)
- ✓Drink at least 64 oz water/day
- ✓Move daily — even 20-minute walks help
- ✓Magnesium citrate or psyllium husk if approved
- ✓Stool softeners (docusate) for short-term relief
⚠ Call your prescriber if: No bowel movement for 5+ days, severe abdominal distension, or rectal bleeding.
Vomiting
Timing
Most common with first dose and dose increases.
Severity
Less common than nausea — usually short-lived.
How to manage
- ✓Slow down on dose escalation if your prescriber agrees
- ✓Stop eating once you feel full — listen to satiety
- ✓Avoid lying flat for 30 minutes after eating
- ✓Anti-nausea Rx (ondansetron) for severe cases
⚠ Call your prescriber if: Vomiting more than once per day for 2+ days, blood in vomit, or severe abdominal pain.
Headache
Timing
Sometimes during early titration. Usually transient.
Severity
Mild. Often related to dehydration or low blood sugar.
How to manage
- ✓Stay well hydrated
- ✓Eat regular small meals — don't skip if appetite drops
- ✓OTC acetaminophen or ibuprofen as needed
⚠ Call your prescriber if: Severe, persistent, or accompanied by vision changes.
Serious side effects — seek immediate care
Wegovy carries a black-box warning for thyroid C-cell tumors (based on rodent data; human risk uncertain). Other rare but serious adverse events:
- Pancreatitis (severe, persistent abdominal pain radiating to the back)
- Gallbladder disease (right-upper-quadrant pain, fever, jaundice)
- Diabetic retinopathy progression (in patients with diabetes)
- Severe allergic reaction (face/throat swelling, breathing difficulty)
- Suicidal thoughts (FDA monitoring as of 2024)
Medical disclaimer: This calculator provides estimates only based on phase 3 clinical trial data and publicly listed prices. It is not medical advice. Real-world weight loss varies significantly. Consult a licensed healthcare provider before starting any medication.