International Normalized Ratio (INR)

International Normalized Ratio – INR) – role in the body

INR (INR) is a standardized blood clotting index used to monitor anticoagulant therapy (primarily warfarin). Together with PTV (prothrombin time) and PTI (prothrombin index) , it reflects the work of the external blood clotting pathway, which depends on vitamin K.

Physiological role:

1. Evaluation of the effectiveness of anticoagulant treatment
2. Diagnosis of coagulation factor synthesis disorders (II, VII, IX, X)
3. Control of liver function (synthesis of clotting factors)
4. Vitamin K deficiency monitoring

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Norms of indicators

Parameter	Normal Range	During Warfarin Therapy
INR	0.8–1.2	2.0–3.0 (typically) 2.5–3.5 (with mechanical heart valves)
PT	11–16 sec	Increases proportionally to INR
PTI	80–120%	Decreases to 20–40%

Note: Standards may vary slightly in different laboratories.

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Symptoms with increased INR (hypocoagulation)

Reasons:

• Overdose of warfarin
• Severe liver diseases
• Vitamin K deficiency
• DIC-syndrome
• Hemophilia

Clinical manifestations:

1. Bleeding problems:

• Nosebleeds
• Gingival bleeding
• Prolonged menstruation

1. Hematomas:

• Spontaneous bruising
• Hemarthrosis (hemorrhage in the joints)

1. Dangerous states:

• Gastrointestinal bleeding (melena, vomiting of ‘coffee grounds’)
• Hemorrhagic stroke
• Internal organ hemorrhage

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Symptoms of low INR (hypercoagulation)

Reasons:

• Insufficient dose of anticoagulants
• Hypervitaminosis K
• Thrombophilia
• Dehydration

Clinical manifestations:

1. Thrombosis:

• Pain and swelling in the extremities (DVT)
• Shortness of breath, chest pain (PE)

1. Ischemic complications:

• Myocardial infarction
• Ischemic stroke

1. With artificial heart valves:

• Prosthetic thrombosis
• Acute heart failure

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Diagnostic value

Ratio of indicators:

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Tactics for deviations

With increased INR (>4.0):

1. Skip taking Warfarin
2. Take vitamin K (1-2 mg orally)
3. When bleeding – fresh frozen plasma
4. Urgent medical consultation

With low INR (<1.5 on therapy):

1. Check compliance with the medication regimen
2. Eliminate vitamin K intake with food (green vegetables)
3. Warfarin dose adjustment

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Interesting facts

• The INR was introduced to standardize the performance of PTV between laboratories
• The INR level may fluctuate at:
• Changing your diet
• Taking antibiotics
• Alcohol excesses
• 30% of warfarin-treated patients experience bleeding episodes in the first year of therapy

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Conclusions

1. INR norm: 0.8-1.2 (without therapy), 2.0–3.5 (on anticoagulants)
2. Increased risk of bleeding (adjust the warfarin dose)
3. Reduction: risk of thrombosis (increase the anticoagulant dose)
4. Most important for patients with:

• Atrial fibrillation
• Mechanical heart valves
• History of thromboembolism

If there are significant deviations in INR, an urgent consultation with a cardiologist or hematologist is required!