Lipitor is a brand name for atorvastatin, a medication used to lower cholesterol levels in the blood. According to GoodRx [2], patients taking statins like Lipitor are advised to avoid consuming grapefruit and grapefruit juice as it can increase the risk of side effects. Grapefruit contains a compound that inhibits the enzyme responsible for breaking down the medication, leading to an increased concentration of the drug in the bloodstream. This can cause an overdose of the drug and increase the risk of side effects. The Mayo Clinic [3] advises that even small amounts of grapefruit can cause a drug interaction, and it is best to avoid it altogether. However, Drug Patent Watch [1] does not provide information on how much grapefruit is needed to trigger Lipitor side effects. Therefore, it is important to consult a healthcare provider before consuming grapefruit or any other citrus fruits while taking Lipitor or any other statin medication.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.goodrx.com/classes/statins/why-cant-i-have-grapefruit-with-my-statin
[3] https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/statin-side-effects/art-20046013