Laboratory (lab) tests are procedures in which a sample of body tissues or fluids is obtained and analyzed to check for signs of illness. A newborn baby typically undergoes a series of lab tests to screen for potential disorders that can cause serious illness and even death if not detected early. Older children are most likely to have a lab test when physical examinations or symptoms indicate the potential presence of disease.

Lab tests used for newborn screenings do not actually diagnose a condition, but merely indicate that further testing is necessary to determine whether or not a newborn has a certain condition. Each state has its own regulations for which screening tests are required of newborns, and the number of tests typically ranges between three and 10.

As children grow older, they may undergo other screening tests. However, in most cases, lab tests are performed on children chiefly to detect illnesses. Lab tests used for this purpose include blood tests, urine tests, stool tests, throat cultures and spinal taps.  

No preparation is required for newborn testing, which usually takes place in the hospital between 24 hours and seven days after a child is born. Other lab tests may require modifications to a child’s diet or medication regimen. Lab tests may be performed differently depending on the nature of the tests.

There are few risks associated with lab tests. Newborns are likely to feel minor pain and to cry when their heel is pricked, and may experience bruising. Children who have blood drawn also may experience minor bruising at the needle insertion site.

Treatments that follow lab tests vary depending on the disorder that is detected.