Research has shown that you can’t take a one-size-fits-all approach to severe asthma management due to differences in phenotypes. So, we developed the International Severe Asthma Registry (ISAR) Eosinophil Phenotype Gradient Algorithm to quantify the eosinophilic phenotype in severe asthma. Using this algorithm, we found 50.3% of patients in UK primary care to be eosinophilic, 22.2% were likely eosinophilic, 21.9% were unlikely eosinophilic and just 5.6% to be non-eosinophilic. What’s more, eosinophilic patients had more exacerbations and greater healthcare resource utilization. In the age of personalized medicine, eosinophilic phenotyping will allow asthma patients to be identified and categorized with and without eosinophilic asthma in primary care and to be referred for phenotype-targeted treatment.