Side effects for GLP-1s may include nausea, vomiting, stomach pain, upset stomach, dizziness, constipation, feeling bloated, belching, gas, headaches and fatigue. If you do experience side effects, they usually subside after a few weeks of your body getting used to the medication. Each patient will receive prescription medication to help combat the side effects should they arise along with directions on dosage to help keep side effects to a minimum. In the most recent clinical trials, less than 5% of people discontinued GLP-1 medications because of side effects.