Final answer:
The major cause of low urea levels in the blood is liver disease, which impairs the liver's ability to produce urea. Malnutrition can also contribute to low urea levels due to protein deficiency for urea production. Dehydration and chronic kidney disease are typically associated with increased urea levels instead.
Step-by-step explanation:
The major cause of low urea levels in the blood is typically related to liver disease. When the liver is not functioning properly, it cannot produce urea efficiently, leading to lower levels in the blood. Malnutrition can also be a contributing factor, as it can result in a deficiency of the proteins needed for the liver to produce urea. On the other hand, conditions such as dehydration and chronic kidney disease (CKD) typically cause elevated urea levels, not lower, due to their effects on renal filtration or fluid balance in the body.
In summary, while malnutrition, dehydration, and CKD can affect blood urea levels, they are more commonly associated with an increase rather than a decrease. Conditions such as liver disorders and malnutrition are more directly linked to reduced urea levels in the bloodstream.