OBJECTIVES: The UK dog population is living longer, raising concerns about their welfare as a result of ageing-related diseases. Our primary objective was to determine when dogs enter the "old age" life stage based on free-text clinical narratives in veterinary electronic health records. In addition, to identify common conditions documented during consultations with old dogs. MATERIALS AND METHODS: Regular expressions were developed for: ageing, elderly, geriatric, senior and old. These were used to search the veterinary clinical narratives within a large database of veterinary electronic health records. A sample of 1000 consultations were then read, and those confirmed as being old age classified according to a modified scheme based on the World Health Organization International Classification of Disease 10th Revision. RESULTS: A total of 832 old age dogs were identified. The age at which veterinary professionals considered dogs to be in old age was over 7.25 years in 95% of patients (median age 12.5 years). This age varied among the most common breeds, with cocker spaniels being younger (median 11.7 years) compared with Jack Russell terriers (14.1 years). Weight-related (289/832 consultations, 35%), musculoskeletal (278, 33%), dental (254, 31%), integumentary (235, 28%) and digestive (187, 22%) conditions were most common. The odds of a dental condition were greater (odds ratio: 2.71, 95% confidence interval: 1.38 to 5.31) and musculoskeletal condition less (odds ratio: 0.36, 95% confidence interval: 0.17 to 0.81) in cocker spaniels than in a mixed breeds reference. CLINICAL SIGNIFICANCE: This metric applied at scale to identify old patients may provide a novel foundation for timely health interventions targeted to dogs at increased risk of developing various age-related conditions.