Urine is one of the main substances used for medical diagnostic tests. Apart from testing the saliva and, more commonly, the blood, a urine test is conducted in order to understand many different conditions. Urine is a waste product from the body and collecting urine is an easy and quick task. It also does not require the patient to be present in a clinical environment, something that is significant when one is considering testing for diseases that may be associated with social stigma such as sexually transmitted diseases. Urine is made up of water along with bilirubin and many other waste products from the body. In a healthy individual, the kidneys filter blood as it flows through them. The clean blood is passed through the body whereas the toxins and waste are passed into the urinary bladder. The bladder then collects this urine and waits for the moment when evacuation can be performed.
Urine tests are sometimes conducted in the morning because the urine tends to be concentrated and full of all sorts of products of the process of metabolism that has occurred while the person is sleeping. Urine can be collected in a jar and sent to a laboratory for analysis. Here, the laboratory will examine the chemical and physical nature of the urine to understand exactly what it is made of. This allows the detection of many different components. It also allows the tester to understand the quantity of each component in the urine.
In healthy individuals, a urine test will reveal the presence of various different components that are considered to be normal. Generally speaking, there is a normal range of values associated with each different component. This normal range is matched to the values found in a patient. Small variations from the normal range in urine test results are generally ignored as they may be caused by small anomalies. A large variation is considered to be diagnostically relevant.
The urine test is generally conducted for some particular reason and there are usually associated symptoms such as discomfort or pain. The urine test results are therefore examined in relation to the problem described by the patient. The doctor can then make an informed diagnosis of the condition based on what has been discovered in the urine test.
This method of testing is particularly effective for law enforcement agencies as well who can use urine samples from suspected drug users in order to establish the presence of drugs in a person's system.