Some people taking atorvastatin may experience side effects such as muscle pain, fatigue, headache, nausea, indigestion, abdominal discomfort, or diarrhea. In rare cases, more serious effects such as elevated liver enzymes or severe muscle injury may occur. Severe muscle pain, dark urine, jaundice, extreme tiredness, or unexplained weakness should be evaluated by a physician. Side effects do not occur in everyone, but regular medical follow-up and blood tests are important during atorvastatin therapy.