Blood test

High prothrombin time in a blood test

Blood test
High prothrombin time in a blood test
Last update: 19/05/2021

What is high prothrombin time in a blood test called?

  • High Prothrombin time (PT)

What is the normal prothrombin time in a blood test?

If you need to know which are the prothrombin time reference ranges or you require more information about prothrombin time in a blood test, you can visit normal prothrombin time in a blood test.

What does a high prothrombin time mean?

A high prothrombin time (PT) in a blood test is a sign of a coagulation disorder. It means that it takes a long time for the blood to form a clot to stop a hemorrhage and therefore there is an excessive bleeding.

Coagulation involves both platelets and proteins (coagulation factors). Coagulation factors are proteins produced by the liver that need vitamin K. Coagulation factors work together in cascade to make a blood clot.

A high prothrombin time (PT) in a blood test may be a sign of:

  • Liver disease (hepatitis, cirrhosis).
  • Vitamin K deficiency (deficit intake on diet, malabsorption, cholestasis).
  • Disseminated intravascular coagulation (DIC) by excessive coagulation factors consumption.

Prothrombin time (PT) test is also used for monitoring oral anticoagulant therapy (with warfarin or acenocoumarol) in people at a high risk for blood clot formation. It is better for this matter to use the INR (International normalized ratio).

A higher than normal prothrombin time (PT) means:

  • Mild prothrombin time (PT) increase (13 - 16 seconds in adults):

    A mild prothrombin time (PT) increase may be just a consequence of the reagents used to measure this time and it does not have any diagnostic importance.

    A visit to your doctor is recommended if you experience any other symptoms like prolonged bleedings. He will decide if additional coagulation tests are required.

  • Moderate prothrombin time increase (16 - 20 seconds in adults):

    A moderate prothrombin time (PT) increase requires a visit to your doctor.

    If after vitamin K injection prothrombin time returns to normal range in about 3 days, malabsorption or vitamin K deficiency may be suspected. If not, the inability of the liver to respond to vitamin K, demonstrates that the liver is damaged and it cannot produce more prothrombin and other coagulation factors, even with abundant vitamin K.

    Another possibility is disseminated intravascular coagulation (DIC). It comes with low fibrinogen value, platelets lower than normal and a high activated partial thromboplastin time (aPTT) in a blood test.

  • Marked prothrombin time (PT) increase (20 - 50 seconds in adults):

    A marked prothrombin time (PT) increase may be related to a liver disease (hepatitis, cirrhosis) if AST and ALT are also high.

    It may be also due to disseminated intravascular coagulation (DIC) in an acute presentation (fibrinogen high, platelets low and activated partial thromboplastin time aPTT high).

    In any case, it is necessary a visit to your doctor because a prothrombin time above 30 seconds may cause prolonged bleeding that are difficult to stop.

  • Severe prothrombin time (PT) increase (> 50 seconds in adults):

    A severe prothrombin time (PT) increase may be related to a liver failure that can lead to important health disorders.

    It is very likely that the liver does not work properly and it is adequate to study the degree of hepatic encephalopathy, the serum creatinine and the arterial pH for a better diagnosis.

Which factors can raise the prothrombin time in a blood test?

There are some health circumstances or drugs than can raise the prothrombin time in a blood test:

  • Alcohol
  • Vitamin K deficiency
  • Diarrhea
  • Vomiting
  • Drugs
    • Antacids
      • Cimetidine
    • Antiarrhythmic agents
      • Amiodarone
    • Antibiotics
      • Metronidazole
      • Tetracycline
    • Antineoplastics
      • Asparaginase
    • Anticoagulants
      • Acenocoumarol
      • Dabigatran
      • Dicoumarol
      • Heparin
      • Warfarin
    • Antidepressant
      • Colestyramine
    • Aspirin
    • Fibrate
      • Clofibrate
    • Uricosuric
      • Allopurinol

Which diseases can raise your prothrombin time in a blood test?

The most common diseases why the prothrombin time can be higher than normal are:

  • Disseminated intravascular coagulation
  • Hepatitis
  • Hepatitis C
  • Hepatic cirrhosis
  • Liver failure
  • Cholestasis
  • Congenital afibrinogenemia
  • Congenital dysfibrinogenemia
  • Congenital hypofibrinogenemia
  • Malabsorption
  • Purpura fulminans
  • Zollinger–Ellison syndrome
  • Vitamin K deficiency bleeding (VKDB) of the newborn

What can I do to lower the prothrombin time in a blood test?

If the prothrombin time (PT) value is higher than normal, you may follow the next tips:

  • Increase your vitamin K intake because it may be due to a vitamin K deficiency. The following foods are rich in vitamin K: cauliflower, spinach, broccoli, asparagus, avocado, sprouts, chickpeas, lettuce, spinach and chard.
  • Avoid alcohol intake. It may harm your liver and reduce the production of coagulation factors needed for the clotting process.

Where can I find more information about prothrombin time in a blood test?

You can visit our pages about:

Which values are considered a high prothrombin time in a blood test?

The following values are considered to be above the normal range:

IMPORTANT: These levels are expressed in seconds. They are an example of a healthy man/woman of about 40 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.

Prothrombin time
Mild prothrombin time (PT) increase
13.1 s13.2 s13.3 s13.4 s13.5 s13.6 s13.7 s13.8 s
13.9 s14 s14.1 s14.2 s14.3 s14.4 s14.5 s14.6 s
14.7 s14.8 s14.9 s15 s15.1 s15.2 s15.3 s15.4 s
15.5 s15.6 s15.7 s15.8 s15.9 s16 s  
Moderate prothrombin time (PT) increase
16.1 s16.2 s16.3 s16.4 s16.5 s16.6 s16.7 s16.8 s
16.9 s17 s17.1 s17.2 s17.3 s17.4 s17.5 s17.6 s
17.7 s17.8 s17.9 s18 s18.1 s18.2 s18.3 s18.4 s
18.5 s18.6 s18.7 s18.8 s18.9 s19 s19.1 s19.2 s
19.3 s19.4 s19.5 s19.6 s19.7 s19.8 s19.9 s20 s
Marked prothrombin time (PT) increase
20.1 s20.2 s20.3 s20.4 s20.5 s20.6 s20.7 s20.8 s
20.9 s21 s21.1 s21.2 s21.3 s21.4 s21.5 s21.6 s
21.7 s21.8 s21.9 s22 s22.1 s22.2 s22.3 s22.4 s
22.5 s22.6 s22.7 s22.8 s22.9 s23 s23.1 s23.2 s
23.3 s23.4 s23.5 s23.6 s23.7 s23.8 s23.9 s24 s
24.1 s24.2 s24.3 s24.4 s24.5 s24.6 s24.7 s24.8 s
24.9 s25 s25.1 s25.2 s25.3 s25.4 s25.5 s25.6 s
25.7 s25.8 s25.9 s26 s26.1 s26.2 s26.3 s26.4 s
26.5 s26.6 s26.7 s26.8 s26.9 s27 s27.1 s27.2 s
27.3 s27.4 s27.5 s27.6 s27.7 s27.8 s27.9 s28 s
28.1 s28.2 s28.3 s28.4 s28.5 s28.6 s28.7 s28.8 s
28.9 s29 s29.1 s29.2 s29.3 s29.4 s29.5 s29.6 s
29.7 s29.8 s29.9 s30 s30.1 s30.2 s30.3 s30.4 s
30.5 s30.6 s30.7 s30.8 s30.9 s31 s31.1 s31.2 s
31.3 s31.4 s31.5 s31.6 s31.7 s31.8 s31.9 s32 s
32.1 s32.2 s32.3 s32.4 s32.5 s32.6 s32.7 s32.8 s
32.9 s33 s33.1 s33.2 s33.3 s33.4 s33.5 s33.6 s
33.7 s33.8 s33.9 s34 s34.1 s34.2 s34.3 s34.4 s
34.5 s34.6 s34.7 s34.8 s34.9 s35 s35.1 s35.2 s
35.3 s35.4 s35.5 s35.6 s35.7 s35.8 s35.9 s36 s
36.1 s36.2 s36.3 s36.4 s36.5 s36.6 s36.7 s36.8 s
36.9 s37 s37.1 s37.2 s37.3 s37.4 s37.5 s37.6 s
37.7 s37.8 s37.9 s38 s38.1 s38.2 s38.3 s38.4 s
38.5 s38.6 s38.7 s38.8 s38.9 s39 s39.1 s39.2 s
39.3 s39.4 s39.5 s39.6 s39.7 s39.8 s39.9 s40 s
40.1 s40.2 s40.3 s40.4 s40.5 s40.6 s40.7 s40.8 s
40.9 s41 s41.1 s41.2 s41.3 s41.4 s41.5 s41.6 s
41.7 s41.8 s41.9 s42 s42.1 s42.2 s42.3 s42.4 s
42.5 s42.6 s42.7 s42.8 s42.9 s43 s43.1 s43.2 s
43.3 s43.4 s43.5 s43.6 s43.7 s43.8 s43.9 s44 s
44.1 s44.2 s44.3 s44.4 s44.5 s44.6 s44.7 s44.8 s
44.9 s45 s45.1 s45.2 s45.3 s45.4 s45.5 s45.6 s
45.7 s45.8 s45.9 s46 s46.1 s46.2 s46.3 s46.4 s
46.5 s46.6 s46.7 s46.8 s46.9 s47 s47.1 s47.2 s
47.3 s47.4 s47.5 s47.6 s47.7 s47.8 s47.9 s48 s
48.1 s48.2 s48.3 s48.4 s48.5 s48.6 s48.7 s48.8 s
48.9 s49 s49.1 s49.2 s49.3 s49.4 s49.5 s49.6 s
49.7 s49.8 s49.9 s50 s    
Severe prothrombin time (PT) increase
50.1 s50.2 s50.3 s50.4 s50.5 s50.6 s50.7 s50.8 s
50.9 s51 s51.1 s51.2 s51.3 s51.4 s51.5 s51.6 s
51.7 s51.8 s51.9 s52 s52.1 s52.2 s52.3 s52.4 s
52.5 s52.6 s52.7 s52.8 s52.9 s53 s53.1 s53.2 s
53.3 s53.4 s53.5 s53.6 s53.7 s53.8 s53.9 s54 s
54.1 s54.2 s54.3 s54.4 s54.5 s54.6 s54.7 s54.8 s
54.9 s55 s55.1 s55.2 s55.3 s55.4 s55.5 s55.6 s
55.7 s55.8 s55.9 s56 s56.1 s56.2 s56.3 s56.4 s
56.5 s56.6 s56.7 s56.8 s56.9 s57 s57.1 s57.2 s
57.3 s57.4 s57.5 s57.6 s57.7 s57.8 s57.9 s58 s
58.1 s58.2 s58.3 s58.4 s58.5 s58.6 s58.7 s58.8 s
58.9 s59 s59.1 s59.2 s59.3 s59.4 s59.5 s59.6 s
59.7 s59.8 s59.9 s60 s60.1 s60.2 s60.3 s60.4 s
60.5 s60.6 s60.7 s60.8 s60.9 s61 s61.1 s61.2 s
61.3 s61.4 s61.5 s61.6 s61.7 s61.8 s61.9 s62 s
62.1 s62.2 s62.3 s62.4 s62.5 s62.6 s62.7 s62.8 s
62.9 s63 s63.1 s63.2 s63.3 s63.4 s63.5 s63.6 s
63.7 s63.8 s63.9 s64 s64.1 s64.2 s64.3 s64.4 s
64.5 s64.6 s64.7 s64.8 s64.9 s65 s65.1 s65.2 s
65.3 s65.4 s65.5 s65.6 s65.7 s65.8 s65.9 s66 s
66.1 s66.2 s66.3 s66.4 s66.5 s66.6 s66.7 s66.8 s
Medically reviewed by our Medical staff on 19/05/2021


  • Concise Book of Medical Laboratory Technology: Methods and Interpretations. 2nd Edition. 2015. Ramnik Sood. ISBN: 978-93-5152-333-8. Pag. 283.
  • A Manual of Laboratory and Diagnostic Test. 9th edition. Frances Fischbach. Marshall B. Dunning III. 2014. Pag 158. ISBN-10: 1451190891.
  • Laboratory tests and diagnostic procedures with nursing diagnoses (8th ed), Jane Vincent Corbett, Angela Denise Banks, ISBN: 978-0-13-237332-6, Pag. 300.
  • Essentials of Medical Laboratory Practice. Constance L. Lieseke, Elizabeth A. Zeibig. 2012. ISBN: 978-0-8036-1899-2 Pag: 319.

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