Side Effects of Weight Loss Injections
What to expect when taking GLP-1 medications like Mounjaro, Wegovy, or Saxenda.
Are Side Effects Common?
Yes. Most people who take GLP-1 medications will experience some side effects, especially when first starting or increasing the dose.
However, for the majority of people, these side effects are mild to moderate and subside over time as the body adjusts to the medication.
Common Side Effects
Nausea
Feeling sick is the most common side effect. It usually passes after a few weeks.
Diarrhea
Loose stools can occur. Stay hydrated.
Vomiting
Usually occurs if you eat too much or eat fatty foods.
Constipation
Can be managed by drinking water and eating fiber.
Stomach Pain
Mild abdominal discomfort or bloating.
Headache
Often due to dehydration or low blood sugar.
Fatigue
Feeling tired or lethargic, especially at the start.
How to Manage Side Effects
Eat smaller meals: Large meals can trigger nausea.
Eat slowly: Stop eating the moment you feel full.
Avoid fatty/fried foods: These are harder to digest and can cause stomach upset.
Stay hydrated: Drink plenty of water throughout the day.
When to See a Doctor
Serious side effects are rare but possible. You should contact your healthcare provider immediately if you experience:
- Severe stomach pain that doesn't go away (could be pancreatitis)
- Changes in vision
- Signs of low blood sugar (dizziness, confusion, sweating)
- Severe allergic reaction (swelling of face/lips, difficulty breathing)
- Lumps or swelling in the neck (thyroid concern)
Medication-Specific Guides
For detailed side effects profiles of each specific medication, please refer to our dedicated guides:
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Medical References & Sources
Last Medically Reviewed: April 2026