Lipid dysmetabolism is emerging as an important contributor to diabetic kidney disease, suggesting that intrarenal lipid accumulation is detrimental to kidney function. This commentary discusses the finding by Yoshioka et al., connecting tubular lipotoxicity induced by an increase in locally produced lysophosphatidylcholine in patients with a fast progression of diabetic kidney disease, known as "fast decliner." Insight into the lipid species in the kidney may prove beneficial for the diagnosis and stratification of patients with diabetic kidney disease.