What the risks are:

This test is often done on people who may have bleeding problems. The risks of bleeding and hematoma in these patients are slightly greater than for people without bleeding problems. In general, risks of any blood test may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)
• Multiple punctures to locate veins

Special considerations:

When you bleed, the body launches a series of activities that help the blood clot. This is called the coagulation cascade. There are three pathways to this event. The PT test looks at special proteins, called factors, found in one of these pathways. It measures the clotting ability of factors I (fibrinogen), II (prothrombin), V, VII, and X. When any of these factors are lacking, the PT is prolonged.