Urea is a common milk ingredient as a part of non-protein nitrogen. Milk urea nitrogen is the most reliable indicator of energy settlement in dairy cattle. Due to the existence of positive correlation between milk urea concentration and the concentration of urea in blood, milk urea concentration is used as a broad indicator of protein-energy balance in dairy cows ration. Also, high urea concentration in milk has a negative impact on health and reproductive performance of cows. In this paper, some production and environmental factors influencing milk urea concentration indirectly associated with intake rate and diet composition are discussed. According to some literature sources the increasing milk yield, milk urea concentration also increases. Milk urea concentration varies according to season and the stage of lactation, while the association between parity and milk urea concentration is positive. According to some authors there is a negative association between milk urea concentration and milk fat and protein percentage. Milk urea concentration is generally lower in samples collected in morning milking which is influenced by feeding-to-milking intervals between morning and evening milking. Body weight is negatively correlated with milk urea concentration in lactating dairy cows. Larger cows have a lower milk urea concentration, and smaller cows a higher milk urea concentration. Finally, there is no doubt that the concentration of urea in milk is useful indicator in feeding management of dairy cows, but for an unbiased analysis of complete situation it is also necessary to include above mentioned non-nutritional factors that affect milk urea concentration.