Background: Interpretating laboratory analytes is crucial when outcomes in elderly patients with chronic diseases and on medications are being interpreted. Elderly individuals constitute a heterogenous group ranging from individuals managing daily life independently to frail individuals; a term widely used although there is no consensus on the definition. The aim of the present study was to investigate the effect of classifying individuals above 80 years of age into healthy, moderately healthy and frail on the interpretation of the laboratory analytes albumin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine and gamma glutamyltransferase (-GT). Methods: Individuals >80 years (n=568), were classified by ADL/MMSE, or Frailty index (FI), including comorbidity, cognitive and physical performance. Results: Three hundred and seventy-eight out of 568 (67%) individuals fell under the same classification with both models. No differences were found between the groups healthy or moderately healthy individuals for any of the analytes, but individuals classified as frail based on FI had lower mean levels of ALT, creatinine and -GT, than individuals classified as frail based on ADL/MMSE (p<0.05). Conclusions: The present study found that using ADL/MMSE or FI to define health status to some extent affected laboratory analytes levels in ≥80-year-olds. The reference intervals provided by NORIP seem to be suitable for the analytes studied for the individuals classified as healthy or moderately healthy, but not for the individuals classified as frail.