Lipitor, also known as atorvastatin, is a medication used to lower cholesterol levels in the blood [1]. According to the Mayo Clinic [3], the most common side effects of Lipitor include muscle and joint pain, diarrhea, constipation, nausea, and stomach pain. These symptoms may occur during the first few months of taking the medication and may improve over time. In rare cases, Lipitor can cause serious side effects such as liver damage, muscle damage, and an increased risk of diabetes [2]. If you experience any symptoms such as muscle weakness, tenderness, or pain, dark urine, yellowing of the skin or eyes, or unexplained fatigue, you should contact your doctor immediately. It is important to note that not everyone who takes Lipitor will experience side effects, and the benefits of the medication in reducing the risk of heart attack and stroke may outweigh the risks [3].

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.drugwatch.com/lipitor/side-effects/
[3] https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/statin-side-effects/art-20046013