Ketosis is a common and significant metabolic disorder in dairy cows during the postpartum period. In affected animals, commercial preparations containing vitamin B₁₂ and phosphorus are frequently used as part of treatment protocols. However, there is limited research regarding serum vitamin B₁₂ and phosphorus concentrations in hyperketonemic cows. This study aimed to evaluate the concentrations of phosphorus and vitamin B₁₂ in the serum of hyperketonemic dairy cows. Blood samples were collected from cows on multiple farms in the Kastamonu district. A total of 25 Holstein cows were utilized in the study, 12 of which exhibited normal serum BHBA levels (H) and 13 of which presented with hyperketonemia (HK). Blood samples were taken within 21 days postpartum and between 4–6 hours after morning or evening feeding. Serum levels of vitamin B₁₂ and phosphorus were then measured. No statistically significant differences were found between the HK and control groups for serum Vit B₁₂ (p=0.327) or phosphorus (p=0.314) concentrations. These findings suggest that despite their altered metabolic state, B₁₂ and phosphorus levels in ketotic cows appear to be independent of serum BHBA concentrations.