What is the purpose of collecting a first-voided morning specimen?

Collecting a first-voided morning specimen serves the purpose of capturing urine that has been held in the bladder overnight. During this time, the kidneys continue to filter blood, and the urine collects, resulting in a sample that is typically more concentrated. This concentration means that various substances, such as proteins, electrolytes, and metabolic waste products, are present in higher amounts compared to specimens collected at other times of the day.

This makes the first-voided morning specimen particularly valuable for diagnostic tests, as it reflects the body's overnight metabolic processes without fluctuations caused by food or drink intake. For instance, a higher concentration of substances can aid in more accurate assessments for conditions such as urinary tract infections or diabetes.