Certain diets (such as high protein/low carbohydrate or high carbohydrate/low protein) may change the effect of theophylline. Tell your doctor if you have any major changes in your diet. Your doctor may need to adjust your dose. Ask your doctor before using theophylline together with caffeine. Using these together may increase some of the side effects of theophylline. This can cause nausea, vomiting, insomnia, tremors, restlessness, uneven heartbeats, and seizure (convulsions). Avoid or limit your consumption of drinks or foods that contain caffeine, such as coffee, tea, cola, and chocolate. Avoid eating foods that are high in fat within one hour before or after taking theophylline and minimize fatty foods generally in your diet, as it can increase the bioavailability of theophylline and thus make it more potent. If you have any questions or concerns regarding your diet, or about foods and drinks that may interact with theophylline, you should discuss them with your doctor.