Tramadol side effects: nausea, vomiting, constipation, lightheadedness, dizziness, drowsiness, or a headache may occur. Some of these side effects may decrease after you have been using this medication for a while. If any of these effects persist or worsen, tell your doctor or pharmacist promptly. To prevent constipation, eat a diet adequate in fiber, drink plenty of water, and exercise. Ask your pharmacist for help in selecting a laxative (such as a stimulant type with stool softener).