GLP-1 Side Effects Guide — Semaglutide, Tirzepatide, Liraglutide, Dulaglutide, Exenatide, Lixisenatide
Patient Guide · GLP-1 Receptor Agonists
Know Before
You Inject
A molecule-by-molecule guide to the side effects of GLP-1 receptor agonists — helping you start your weight-loss journey with clear eyes and confident questions for your doctor.
⚕️ Medical Disclaimer: This guide is for educational purposes only. Always consult your physician before starting, changing, or stopping any medication. Individual side-effect profiles vary.
How GLP-1 Agonists Work
GLP-1 receptor agonists mimic a natural gut hormone released after eating. They slow stomach emptying, signal the brain to reduce hunger, stimulate insulin release, and suppress glucagon — leading to reduced calorie intake and weight loss over time.
🧠Reduces appetite
🐌Slows digestion
💉Boosts insulin
⚖️Promotes weight loss
Side Effect LegendVery Common (>10%)GI-RelatedInjection SiteRare / <1%Serious – Seek HelpOther
Molecule-by-Molecule Breakdown
Sem
Semaglutide
Ozempic® · Wegovy® · Rybelsus®
SC / Oral
Weekly / daily
Gastrointestinal
NauseaVomitingDiarrhoeaConstipationBloatingBelching
General
Decreased appetiteFatigueHeadache
Serious / Rare
Acute pancreatitisGallstonesThyroid C-cell tumours (animal)Retinopathy worsening
★ Ozempic Face:Rapid fat loss may cause facial changes. Muscle loss ("Ozempic body") reported if protein intake is inadequate.
Lira
Liraglutide
Victoza® · Saxenda®
SC
Daily
Gastrointestinal
Nausea (~40%)DiarrhoeaConstipationVomiting
General
HeadacheIncreased heart rate
Serious / Rare
Acute pancreatitisGallbladder diseaseSuicidal ideation (class warning)
★ Daily dosing means more consistent GI side effects early on. Titrate slowly over 4–5 weeks.
Tirz
Tirzepatide
Mounjaro® · Zepbound®
SC
Weekly
Gastrointestinal
Nausea (up to 45%)Diarrhoea (up to 30%)VomitingConstipationHeartburn
General
Decreased appetiteFatigueHair thinning
Serious / Rare
Acute pancreatitisGallbladder diseaseIleus / bowel obstruction
★ Dual GIP+GLP-1 agonist — most potent weight loss (~20–22%) but GI side effects can be more pronounced.
Dula
Dulaglutide
Trulicity®
SC
Weekly
Gastrointestinal
NauseaDiarrhoeaVomitingConstipation
General
FatigueHeadacheIncreased HR (5–10 bpm)
Serious / Rare
PancreatitisCholelithiasis
★ Generally better tolerated than daily agents. Pre-filled pen is needle-hidden for convenience.
ℹ️ Price data coming soon
Exe
Exenatide
Byetta® · Bydureon®
SC
2x daily / Weekly
Gastrointestinal
Nausea (most frequent)VomitingDiarrhoeaAcid reflux
Injection Site
Nodule formation (~50%)Erythema
Serious / Rare
Acute pancreatitisKidney injury
★ First GLP-1 agonist approved. Significant injection-site nodules with the long-acting formulation.
ℹ️ Price data coming soon
Lixi
Lixisenatide
Lyxumia® · Adlyxin®
SC
Once daily
Gastrointestinal
NauseaVomitingDiarrhoeaConstipation
General
HeadacheDizzinessUTI
Serious / Rare
PancreatitisAnaphylaxis
★ Short-acting agent — strong effect on postprandial glucose but modest weight loss (~2–3 kg).
ℹ️ Price data coming soon
At-a-Glance Comparison
| Molecule | Nausea Risk | Frequency | Weight Loss | Pancreatitis |
|---|---|---|---|---|
Semaglutide | ●●● | Weekly / Oral | ~15–17% | ⚠ |
Liraglutide | ●●● ~40% | Daily | ~8–10% | ⚠ |
Tirzepatide | ●●● ~45% | Weekly | ~20–22% | ⚠ |
Dulaglutide | ●●○ | Weekly | ~5–7% | ⚠ |
Exenatide | ●●○ | 2x/Weekly | ~3–5% | ⚠ |
Lixisenatide | ●●○ | Once daily | ~2–3% | ⚠ |
🚨 Red-Flag Symptoms — Stop & Seek Emergency Care
🔥
Severe Abdominal Pain
Persistent, radiating to back — may indicate pancreatitis.
💛
Jaundice / RUQ Pain
Gallstones or gallbladder inflammation.
😵
Extreme Dehydration
Persistent vomiting + dark urine + confusion.
🤧
Swelling of Face / Throat
Signs of anaphylaxis — call emergency services.
👁️
Vision Changes
Semaglutide can worsen diabetic retinopathy.
🧠
Mood Changes / Suicidal Thoughts
Class-level warning — contact your doctor immediately.
Who Should Avoid GLP-1 Agonists?
🚫 Personal/family history of medullary thyroid carcinoma
🚫 Multiple Endocrine Neoplasia type 2 (MEN2)
🚫 History of acute pancreatitis
🚫 Severe gastroparesis
🚫 Pregnancy or planning pregnancy
🚫 Severe renal impairment (exenatide contraindicated)
Tips to Reduce Side Effects
01
Start low, go slow. Most GI effects improve within 4–8 weeks.
02
Eat smaller portions. Smaller, more frequent meals reduce nausea.
03
Avoid trigger foods. Fatty, spicy, or high-sugar foods amplify GI symptoms.
04
Stay hydrated. Drink plenty of clear fluids — vomiting can lead to dehydration.
05
Inject at night. Sleep through the initial nausea window.
06
Rotate injection sites. Prevent nodules, bruising, and skin reactions.
07
Prioritise protein. Eat ≥1.2g protein/kg body weight to prevent muscle loss.
08
Strength train. Resistance exercise helps preserve muscle mass while losing fat.