Prothrombin Blood Test Results Explained


The prothrombin blood test is used to help diagnose the presence of bleeding that is unexplained. It may also be ordered when there are inappropriate blood clots that have been discovered. Used in conjunction with the PTT blood test, a normalized ratio will be calculated and then used to monitor those who are taking medications that are designed to thin the blood.

This is because human blood has several coagulation factors that help the body form blood clots to naturally stop bleeding. Should an injury occur and bleeding begin, the coagulation factors follow a series of steps that will eventually form a clot. If this doesn’t happen, then there isn’t a sufficient quantity of at least one of the coagulation factors and this interrupts the clotting process, causing bleeding to be prolonged.

If there is a surplus of quantity in the coagulation factors, then inappropriate clotting may occur, which can be a medical emergency.

Why Do I Need to Have the Prothrombin Blood Test?

The prothrombin blood test is used to monitor the effectiveness of a blood-thinning medication like warfarin, or its brand name Coumadin. Because this medication affects the coagulation steps that form clots, it requires consistent monitoring for results to remain effective. The goal of medication therapy in this instance is to balance a prevention of inappropriate clots without having excessive monitoring.

This blood test will help a medical provider be able to determine if clotting is within the desired range for that patient.

When Is the Prothrombin Blood Test Necessary?

Blood-thinning medications are prescribed for several different conditions. Sometimes clotting or excessive bleeding may not be present for the prescription to be authorized. Individuals who have artificial heart valves may be given warfarin, which would then qualify them to receive ongoing prothrombin blood tests.

Individuals with irregular heartbeats, have suffered a first heart attack and have specific risk factors present, or have suffered from an inappropriate blood clot will also receive warfarin. That would mean they would also be monitored using this blood test.

Other circulation factors may also cause warfarin to be added to a treatment plan.

When to Ask About the Prothrombin Blood Test

The prothrombin blood test is most frequently ordered to monitor the effectiveness of medication. It may also be ordered whenever someone may be suffering from the signs or symptoms of either excessive bleeding or inappropriate clotting.

This may include unexplained bleeding, prolonged nosebleeds, or bruises that easily form, spread, and take a prolonged time to heal. Individuals with bleeding gums without the evidence of gum disease may also be evaluated through this blood test. Certain acute conditions which may cause bleeding or clotting may also qualify, as do certain chronic conditions that can affect clotting, such as liver disease.

The prothrombin blood test is also ordered prior to certain surgeries if there may be an increased risk of blood loss occurring or if the individual has a history of bleeding or easy bruising.

What Do My Prothrombin Blood Test Results Mean?

The test results from the prothrombin blood test are dependent on whether or not an individual is taking a blood-thinning medication. For those on a drug like warfarin, the international normalized ratio should be between 2-3. If there is a higher risk of a blood clot forming, then the results should be between 2.5-3.5.

If a blood thinner is not being taken, then the blood test results may be communicated as being “normal” or “prolonged.” The prothrombin test results will then be compared to the PTT results to determine a potential diagnosis. Here is what to expect.

If prothrombin is prolonged, but PTT is normal: This indicates the presence of liver disease or a vitamin deficiency if an individual is not taking warfarin.

If prothrombin is normal, but PTT is prolonged: This indicates the presence of a lupus anticoagulant, an autoantibody against a specific factor, or von Willebrand disease.

If prothrombin is prolonged and PTT is prolonged: This indicates the presence of severe liver disease or a possible warfarin overdose.

If prothrombin is normal, but PTT is slightly prolonged or normal: This may indicate normal clotting, but it may also be evidence of a mild deficiency.

The consumption of alcohol is known to affect prothrombin blood test results. Certain antibiotics may also cause interference, as well oral contraceptives or hormone therapies. Vitamin K can decrease the test results that are obtained. You may also be asked specific questions about your diet.

This will allow the prothrombin blood test to be as accurate as possible.