Lipitor is a brand name for the drug atorvastatin, which is used to lower cholesterol levels in the blood. According to the sources provided, Lipitor should be taken once a day, at the same time each day, with or without food [1][2]. It is recommended to take it at night, as the body produces more cholesterol during this time [2]. However, it is important to follow the instructions given by the doctor or pharmacist, as the dosage and frequency of Lipitor intake may vary depending on the individual's condition and response to the medication [2]. It is also advised to avoid consuming grapefruit or grapefruit juice while taking Lipitor, as it may increase the risk of side effects [2][3]. It is important to note that Lipitor should only be taken under the supervision of a healthcare professional and should not be shared with others [1].

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.nhs.uk/medicines/atorvastatin/how-and-when-to-take-atorvastatin/
[3] https://www.drugs.com/medical-answers/eat-food-taking-atorvastatin-3565628/