The aim of the study was to determine the effects of betaine and increased supplementation of vitamins B₆, B₁₂ and folie acid in pig diets on blood urea and homocysteine levels. The experiment was conducted on 64 growing-fattening pigs. The parameters under study did not differ significantly among the groups. However, in animals fed on betaine non-supplemented diets, the urea level tended to be higher, while homocysteine was lower when diets contained higher levels of B vitamins. The urea level was uniform in pigs fed diets supplemented with betaine, and homocysteine varied to a very small extent.