There are very few risks or side effects associated with blood tests. Sometimes, bruising may occur at the site of injection. This can be minimized and alleviated by keeping direct pressure on the spot for several minutes after the syringe has been removed.

In rare cases, the vein used to obtain the sample may become inflamed or infected. Applying warm compresses to the spot several times daily can help reduce swelling.

People with bleeding disorders or who are taking anticoagulants, including aspirin, may have problems with continued bleeding. Those who experience these side effects should consult their physician.