Hi, thanks for your question. Short answer: Yes timolol can cause fatigue and slower heart beat. Timolol belongs to a group of medications, called non-selective Beta Blockers, which slows down heart rate as one of its actions. These medications also cause fatigue in many patients. Usually, these symptoms get better with time. However, if your heart rate is below normal (less than 60 beats per minute) or the fatigue is bothering you a lot, then you should see your doctor who might review your medications, and if deemed necessary, they would reduce the dose of Timolol or switch to another drug/treatment. (Hope this helps. Please feel free to ask for any further explanation.