There are few risks associated with lab tests. Newborns are likely to feel pain and to cry when their heel is pricked. There may be a small amount of bruising following the test.

Children who have blood drawn also may experience minor bruising at the needle insertion site. This can be minimized by keeping direct pressure on the spot for several minutes after the needle has been removed.

In rare situations, the vein used to obtain the sample may become inflamed (phlebitis) or obstructed (thrombosis). Applying warm compresses to the spot several times daily can help reduce the swelling.

Children with bleeding disorders and those who are taking anticoagulants (blood thinners) may have problems with continued bleeding. Children who experience these side effects should be taken to their physician.

There is a small risk of infection with a spinal tap. Other rare side effects that may occur include allergic reaction or damage to the spinal cord.