Interleukin-6 (IL-6) is a marker of severe inflammation which quickly rises in the blood in response to infections & tissue injuries. IL-6 triggers release of other markers of acute inflammation such as CRP. Your body can produce an excessive response to inflammation which can be harmful for you. This is called "Inflammatory Cascade". This is seen in Covid-19 and other chronic diseases. This test is used to monitor Covid-19 patients who are at a greater risk of developing complications specially lung damage.