Frequencies are from the STEP-1 and SURMOUNT-1 trials. Nausea is the single most common GLP-1 side effect — 44% of patients on Wegovy report it, typically in the first 4-8 weeks and again at each dose escalation. Constipation (24%), diarrhea (30%), vomiting (24%), and decreased appetite (35%) round out the top GI complaints.
Most GI side effects resolve over 1-4 weeks as the body adapts. Slowing the titration schedule (staying on a lower dose for an extra month) typically helps. Hydration, smaller frequent meals, and avoiding high-fat foods reduce nausea.
Less common but more serious: acute pancreatitis (rare, <1% in trials), gallbladder disease (~2% on tirzepatide), and acute kidney injury secondary to dehydration from vomiting. Stop the drug and seek care for severe abdominal pain or persistent vomiting.
A dose-titration timeline tool maps expected symptoms to each phase.