Background: Reference intervals are widely used as decision tools, providing the physician with information about whether the analyte values indicate ongoing disease process. Reference intervals are generally based on individuals without diagnosed diseases or use of medication, which often excludes elderly. The aim of the study was to assess levels of albumin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine and γ-glutamyl transferase (γ-GT) in frail, moderately healthy and healthy elderly indivuduals. Methods: Blood samples were collected from individuals >80 years old, nursing home residents, in the Elderly in Linköping Screening Assessment and Nordic Reference Interval Project, a total of 569 individuals. They were divided into three cohorts: frail, moderately healthy and healthy, depending on cognitive and physical function. Albumin, ALT, AST, creatinine and γ-GT were analyzed using routine methods. Results: Linear regression predicted factors for 34% of the variance in albumin were activities of daily living (ADL), gender, stroke and cancer. ADLs, gender and weight explained 15% of changes in ALT. For AST levels, ADLs, cancer and analgesics explained 5% of changes. Kidney disease, gender, Mini Mental State Examination (MMSE) and chronic obstructive pulmonary disease explained 25% of the variation in creatinine levels and MMSE explained three per cent of γ-GT variation. Conclusions: Because a group of people are at the same age, they should not be assessed the same way. To interpret results of laboratory tests in elderly is a complex task, where reference intervals are one part, but far from the only one, to take into consideration.