GLP-1 Side Effects Guide
What to expect when taking semaglutide, tirzepatide, or other GLP-1 medications. Frequency data from clinical trials, management strategies, and warning signs that require medical attention.
The Reality Check
Most people experience some gastrointestinal side effects when starting GLP-1 medications. Nausea, diarrhea, and constipation are common—not rare. The good news: these effects typically improve over time as your body adapts. Serious side effects are uncommon but require immediate attention.
Most Common Side Effects
Based on pooled data from STEP (semaglutide) and SURMOUNT (tirzepatide) trials. These rates reflect what percentage of participants experienced each side effect.
Nausea
31-44%Most common side effect. Usually peaks during dose increases and improves within days to weeks. For most people, it's manageable—mild to moderate queasiness rather than severe nausea.
Management Strategies:
- •Eat smaller, more frequent meals instead of large portions
- •Avoid high-fat, greasy, or spicy foods
- •Take your injection at night if nausea is worse during the day
- •Try ginger tea, crackers, or other bland foods
- •Ask your doctor about slowing dose escalation if severe
Diarrhea
23-30%Second most common gastrointestinal effect. Usually temporary, lasting a few days to a couple weeks after dose increases. Rarely severe enough to cause dehydration.
Management Strategies:
- •Stay well-hydrated (water, electrolyte drinks)
- •Follow the BRAT diet temporarily (bananas, rice, applesauce, toast)
- •Avoid dairy, caffeine, and high-fiber foods until it resolves
- •Talk to your doctor if it persists beyond a few days
Constipation
17-24%GLP-1 medications slow gastric emptying, which can lead to constipation in some people. Paradoxically, others experience diarrhea—individual responses vary.
Management Strategies:
- •Increase fiber intake gradually (fruits, vegetables, whole grains)
- •Drink plenty of water throughout the day
- •Stay physically active—movement helps digestion
- •Consider over-the-counter stool softeners if needed
- •Consult your doctor if constipation becomes chronic
Vomiting
12-24%Less common than nausea, but still affects a notable percentage of users. Usually occurs during dose escalation. Persistent vomiting requires medical attention.
Management Strategies:
- •Stop eating when you feel full—don't push it
- •Sip clear liquids slowly between meals
- •Avoid strong food odors that trigger nausea
- •Contact your doctor if: vomiting persists, you can't keep liquids down, or you show signs of dehydration
Abdominal Pain / Discomfort
11-20%General stomach discomfort, cramping, or bloating. Usually mild and related to delayed gastric emptying. Severe or persistent pain requires evaluation.
When to Worry:
- •Severe, persistent upper abdominal pain radiating to your back (possible pancreatitis)
- •Right upper quadrant pain especially after eating (possible gallbladder issues)
- •Pain with fever, jaundice, or persistent vomiting (seek immediate care)
Serious Side Effects (Rare)
These are uncommon but require immediate medical attention. Know the warning signs.
Pancreatitis
Inflammation of the pancreas. Rare in trials (less than 1%), but potentially serious. GLP-1 medications may increase risk compared to placebo, though absolute risk remains low.
Warning Signs:
- •Severe, persistent upper abdominal pain that may radiate to your back
- •Pain that doesn't improve with position changes or over-the-counter meds
- •Nausea and vomiting that won't stop
- •Tender abdomen when touched
Action: Stop medication and seek immediate medical care if you suspect pancreatitis.
Gallbladder Disease
Rapid weight loss (regardless of method) increases gallstone risk. Gallbladder problems occurred in ~2-3% of participants in weight loss trials, compared to ~1% with placebo.
Warning Signs:
- •Pain in the right upper abdomen, especially after eating fatty meals
- •Pain between shoulder blades or in right shoulder
- •Nausea or vomiting along with abdominal pain
- •Fever, chills, or yellowing of skin/eyes (jaundice)
Action: Contact your doctor if you experience these symptoms. Severe cases require emergency care.
Thyroid Tumors (Boxed Warning)
GLP-1 medications carry a boxed warning about thyroid C-cell tumors based on rodent studies. This has NOT been confirmed in humans—no cases of medullary thyroid carcinoma were reported in clinical trials. Still, the warning exists out of caution.
Who Should NOT Use These Medications:
- •Personal history of medullary thyroid carcinoma (MTC)
- •Family history of MTC
- •Multiple endocrine neoplasia syndrome type 2 (MEN 2)
Note: If you develop a lump or swelling in your neck, hoarseness, trouble swallowing, or shortness of breath, contact your doctor.
Hypoglycemia (Low Blood Sugar)
Rare in people without diabetes. Risk increases if you're taking GLP-1 medications along with insulin or sulfonylureas for diabetes management.
Warning Signs:
- •Shakiness, sweating, rapid heartbeat
- •Dizziness, confusion, irritability
- •Hunger, headache, blurred vision
Action: If you have diabetes and take other medications, monitor blood sugar regularly. Your doctor may need to adjust other medications.
Kidney Problems
Dehydration from vomiting or diarrhea can worsen kidney function, especially in people with existing kidney disease. Acute kidney injury has been reported in post-marketing surveillance.
Prevention:
- •Stay well-hydrated, especially if experiencing GI side effects
- •Tell your doctor if you have existing kidney disease
- •Seek care if you can't keep fluids down
When to Call Your Doctor
Seek Immediate Care
- •Severe abdominal pain that won't go away
- •Persistent vomiting preventing fluid intake
- •Signs of severe dehydration (dizziness, dark urine, no urination)
- •Severe allergic reaction (swelling, difficulty breathing, rash)
- •Chest pain or rapid heartbeat
- •Vision changes or severe headache
Contact Doctor Soon
- •Side effects that persist beyond 2-3 weeks
- •Weight loss has stopped despite adherence
- •New lump or swelling in your neck
- •Worsening depression or mood changes
- •Signs of gallbladder issues (right upper pain after eating)
- •Questions about dose adjustment or medication changes
Long-Term Safety
Most clinical trials for weight loss lasted 68-72 weeks (about 16-18 months). Liraglutide has been available since 2014, giving us about a decade of real-world data. Semaglutide and tirzepatide are newer, with less long-term data available.
We don't yet know the full safety profile of taking these medications for 5, 10, or 20+ years. Post-marketing surveillance continues to track outcomes as more people use these drugs over longer periods.
What we do know: cardiovascular outcome trials (STEP-HFpEF, SELECT for semaglutide) show cardiovascular benefits rather than harms. No unexpected safety signals have emerged so far. But "so far" is the key phrase—we're still learning.
Learn More About GLP-1 Medications
Compare efficacy, dosing protocols, and costs across different medications.
Medical Disclaimer
This information is for educational purposes only and does not constitute medical advice. Side effect data is drawn from published clinical trials. Individual experiences vary. We are not healthcare providers. If you experience concerning symptoms while taking GLP-1 medications, contact your doctor or seek emergency care.