What is a normal INR reading?
In healthy people an INR of 1.1 or below is considered normal. An INR range of 2.0 to 3.0 is generally an effective therapeutic range for people taking warfarin for disorders such as atrial fibrillation or a blood clot in the leg or lung.
How do you measure international normalized ratio?
The INR is derived from prothrombin time (PT) which is calculated as a ratio of the patient’s PT to a control PT standardized for the potency of the thromboplastin reagent developed by the World Health Organization (WHO) using the following formula: INR = Patient PT ÷ Control PT.
What units is INR measured in?
The INR has no units (it is a ratio) and is determined to one decimal place. The first step of the INR calculation is to “normalize” the PT by comparing it to the mean normal prothrombin time (MNPT), the geometric mean of the prothrombin times of the healthy adult population.
What is international normalized ratio?
The international normalized ratio (INR) is a calculation based on results of a PT and is used to monitor individuals who are being treated with the blood-thinning medication (anticoagulant) warfarin (Coumadin®). The PT and INR are used to monitor the effectiveness of the anticoagulant warfarin.
What is ISI in PT INR?
The INR was devised to standardize the results. Each manufacturer assigns an ISI value (International Sensitivity Index) for any tissue factor they manufacture. The ISI value indicates how a particular batch of tissue factor compares to an international reference tissue factor.
What is an INR measuring?
An INR test measures the time for the blood to clot. It is also known as prothrombin time, or PT. It is used to monitor blood-thinning medicines, which are also known as anticoagulants. The INR, or international normalised ratio, can also be used to check if you have a blood clotting problem.
Is an INR of 1.7 ok?
The INR goal for people who take warfarin is usually from 2 to 3.5. A value higher than 3.5 increases the risk of bleeding problems. Many things can affect the way warfarin works. Some natural health products and other medicines can make warfarin work too well.
What causes an INR level to be low?
Common causes of a low INR, or of a blood clot in general, include: Taking too low of a dose of an anticoagulant medication. Missing a dose of anticoagulant medication or cutting back on the dose without doctor approval.
What do I expect if I have low INR?
With a very high INR above about 3.5 to 4, you may suffer with bloody nose, blood in your stools, bruising. With a LOW INR, below about 1.5 to 2.0 if you’re taking blood thinners, you may be more prone to throwing clots which could result in stroke, pumonary embolisms, deep vein thrombosis, heart attacks.
What are normal INR levels?
Normal INR Levels. The normal range for a healthy person not using warfarin is 0.8–1.2. However, this is a dangerously low INR for a person using Warfarin.
What is the critical value for INR?
Properly anticoagulated patients INR values will range between 2.0-3.0. However, if the patient is being treated for recurrent embolism or have mechanical prosthetic heart valves a range of 2.5-3.5 is desirable. INR levels above 4.9 are considered Critical values and are immediately phoned to the Physician.