This is usually done by a health professional (usually a midwife or health visitor) during a home visit when your baby is 5 days old. A very small sample of blood is collected by pricking your baby's heel, using a special device and squeezing out a few drops of blood on to a blood spot card. Although this test may be uncomfortable, it is over very quickly. The sample is sent away for testing, and you will receive the results by letter or phone in due course.
This is a companion discussion topic for the original article at https://patient.info/pregnancy/newborn-baby-screening-tests/bloodspot-test