Lipitor, also known as atorvastatin, is a medication used to lower cholesterol levels in the blood. According to the information provided by Drugs.com, Lipitor starts reducing cholesterol levels within 2 weeks of starting the medication [1]. However, it may take up to 4-6 weeks to see the full effects of the drug on cholesterol levels [1].

It is important to note that Lipitor is most effective when used in conjunction with a low-fat diet and regular exercise [1]. Additionally, Lipitor works by blocking an enzyme in the body that is used to produce cholesterol [1].

It is also worth noting that, according to DrugPatentWatch.com, Lipitor's patent expired in November 2011 [2]. This means that generic versions of the drug are now available on the market, which may make the medication more accessible and affordable for some patients.

In summary, Lipitor starts reducing cholesterol levels within 2 weeks of starting the medication, but it may take up to 4-6 weeks to see the full effects. It is most effective when used in conjunction with a low-fat diet and regular exercise.

Sources:

1. <https://www.drugs.com/lipitor.html>
2. <https://www.drugpatentwatch.com/drugs/lipitor>