There isn't an exact science behind this, but generally it can take around 3 to 4 months before someone will see any benefits of milk thistle on their health, and this is after daily intake of some form of milk thistle. Milk thistle is promoted as a dietary supplement for hepatitis, cirrhosis, jaundice, diabetes, indigestion, and other conditions. Avoid using milk thistle and simeprevir together. Sirolimus (Rapamune). Taking milk thistle with this immunosuppressant might change the way your body processes the medication.