Choline is an essential nutrient that the body needs for many functions, including building cell membranes, supporting nerve signaling, and helping the liver process fats. Although the body can make small amounts, most choline comes from the diet through foods such as eggs, meat, fish, and certain vegetables. A choline blood test measures the level of this nutrient circulating in the blood. This test is used to assess a person's choline status, which may be of interest when evaluating nutritional intake or investigating concerns related to liver function, nerve health, or specific dietary needs. It is not a routinely ordered test and is most often used in nutritional or research settings.