There are very few risks or side effects associated with blood tests. Occasionally, bruising is reported at the injection 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). Applying warm compresses to the spot several times daily can help reduce the swelling.

Those with bleeding disorders and those who are taking anticoagulants (including aspirin) may have problems with continued bleeding. Patients who experience these side effects should consult with their physician.