Although acquired mutations in KIT are commonly detected in various categories of mastocytosis, the methodologies applied to detect and quantify the mutant type and -burden in various tissues and cells are poorly defined. We here propose a consensus on methodologies used to detect KIT mutations in patients with mastocytosis at diagnosis and in the follow up with sufficient precision and sensitivity in daily practice. In addition, we provide recommendations for sampling and storage of diagnostic material as well as a robust diagnostic algorithm. Using highly-sensitive assays, KIT D816V can be detected in peripheral blood leukocytes in most patients with systemic mastocytosis (SM) which is a major step forward in screening and SM detection. In addition, the KIT D816V allele burden can be followed quantitatively during the natural course or during therapy in these patients. Our recommendations should greatly facilitate diagnostic and follow up investigations in SM in daily practice as well as in clinical trials. In addition, the new tools and algorithms proposed should lead to a more effective screen, early detection of SM, and help avoid unnecessary referrals.