Prothrombin Time

Pro Time, PT (Prothrombin Time)

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Taking medicines that can affect the action of blood thinners (such as warfarin) and vitamin K. These include antibiotics, aspirin, cimetidine (Tagamet), barbiturates, birth control pills, hormone replacement therapy (HRT), and vitamin K supplements.
• Having severe diarrhea or vomiting that causes fluid loss and dehydration. This may make the PT time longer. If diarrhea is caused by poor absorption of nutrients, vitamins, and minerals from the intestinal tract (malabsorption syndrome), the PT may be longer because of a lack of vitamin K.
• Eating foods that have vitamin K, such as beef liver, pork liver, green tea, broccoli, chickpeas, kale, turnip greens, and soybean products.
• Drinking a lot of alcohol.
• Taking laxatives.
• Taking some herbal products or natural remedies.

Go to previous section	Go to top of page	Go to next section
Author:	Jan Nissl, RN, BS	Last Updated: September 25, 2006
Medical Review:	Patrice Burgess, MD - Family Medicine Joseph O'Donnell, MD - Hematology/Oncology
© 1995-2008 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.