If you have been taking milk thistle It is suggested that you stop about 2 to 4 weeks before liver-flushing. Liver -cleaning consists of a series of liver-flushes separated by 2 to 4 weeks. Many people are able to clean themselves after 8 to 12 flushes but older and chronically ill people may need significantly more. When you have finished flushing you can start to take milk thistle after 1 to 2 weeks.