Impact of blood donation on serum cobalamin and folic acid concentrations in dogs.

Serum cobalamin (B12) and folic acid (B9) support bone marrow and intestinal activity. While blood donation (BD) is known to affect haematological and iron status, its impact on vitamin B12/B9 levels is poorly studied in humans and not investigated in dogs. This study aimed to evaluate the impact of BD on serum vitamin B12 and vitamin B9 concentrations in blood donor dogs. Eighty-nine blood donor dogs were included from June 2024 to March 2025. Serum vitamin B12 and vitamin B9 were measured, and the corresponding complete blood count was analysed. Age, sex, breed, the total number of BD and BD annual frequency (≤2/year and >2/year) were registered. Forty dogs (45%) donated blood ≤2/year, while 49 (55%) donated >2/year. Median number of total BD/years was 4.5 donations (range: 1-16 total BD). Considering the reference interval, 7 dogs (8%) had decreased vitamin B12 levels (median 557; range 88-2400 pg/mL; RI 300-908 pg/mL) and 25 (28%) showed low serum vitamin B9 levels (median 9.2 pg/mL, range 2.5-24 pg/mL; RI 7.7-24 pg/mL). In the present study, although some canine blood donors showed lower vitamin B12 and vitamin B9 concentrations, no significant associations were observed between vitamin levels and donation frequency or age/sex variables.