INR Self Testing

Categories: Medical Messages,News

This article is currently being updated and revised. Please consult with your healthcare provider in the interim should you have questions about INR self-testing.

INR Self Testing

Stephan Moll, MD; University of North Carolina, Chapel Hill, NC Jack Ansell, MD; Boston University Medical Center; Boston, MA

INR Self TestingWarfarin and the INR

If you are on warfarin (Coumadin®, Jantoven®), you regularly need a blood test called prothrombin time, protime or PT, with the result of the test called INR – International Normalized Ratio. Monitoring of the INR is essential because too high an INR puts an individual at risk for bleeding and too low an INR at risk for clotting. There are four different ways to get your INR tested and warfarin adjusted:

  1. Traditional way: In the physician’s office or anticoagulation clinic, blood is drawn from a vein stick and then sent to a laboratory. It takes some time to get the INR value back: 1-2 hours at the fastest, 1-2 days if the blood sample needs to be sent to an outside laboratory. You will need to be called at home once the result is back and your new warfarin dose needs to be discussed. This is a somewhat cumbersome and time-consuming way to manage warfarin.
  2. Physician office point-of-care testing: In your physician’s office a small drop of blood from a finger stick  can be transferred onto a small, so called “point of care instrument” (POC device). The INR result is available within minutes, while you are still in your physician’s office. You can, therefore, immediately be informed of the result and your further warfarin dosing discussed with you. These POC instruments make warfarin management easier and lead to improved, faster and more efficient communication with patients.
  3. INR self-testing: You can use these same “point of care” instruments at home or when traveling to check your INR. You can then inform your physician, anticoagulation clinic pharmacist or nurse, or the IDTF (independent diagnostic testing facility; further discussion below) of the result (by phone or through the Internet) and get instructions on further dosing of your warfarin. This is referred to as “Patient self testing” (PST).
  4. INR self-management: Patients who use the “point of care” instruments themselves can not only check their own INR, but can also be taught to adjust their own warfarin dosing. While this type of anticoagulant management has gained acceptance in the medical community in some European countries, it has, at this point, not been promoted by the healthcare systems in the U.S. or Canada.

Reasons to do INR self testing

High quality anticoagulation therapy can certainly be delivered through physicians’ offices and  anticoagulation clinics. For many patients these are good, effective, safe and convenient set-ups. However, for many people, INR self testing is also a good and attractive option. There are some powerful advantages of INR self testing over routine office-based care.

  • Foremost, several studies (summarized in reference 1) have shown that individuals who monitor their own INR have (a) slightly less bleeding and clotting complications, and (b) are more often in the target INR range, i.e. their anticoagulant therapy is better controlled;
  • Patient self testing can be more convenient and save you time, as you do not have to go to the physician’s office for testing. This can give you more freedom, particularly, if you have to rely on a caregiver for transportation or have a long drive to your physician’s office;
  • It may give you a sense of security, as you can easily check the INR at times when you suspect that the INR may be too high or too low, such as when you have started a new medication, discontinued a medication, are sick, or have changed your diet. Also, if you have a history of fluctuating (unstable) INRs and need to have frequent INR checks, it is easier to test more frequently if you have your own instrument at home;
  • It may empower you by having you actively involved in your medical care;
  • It allows you to travel without having to track down service providers for INR testing and deal with bureaucracy and language barriers;
  • And lastly, if it is difficult to get a venous sample from you from an i.v. stick and your physician’s office  does not have a “point of care” instrument, the self testing from a finger stick may be a good solution for  you.

Thus, there are several good reasons for you to consider self testing and ask your physician about it.  Similarly, these same reasons should prompt physicians to make you aware of the possibility to do INR self testing.

Who is suitable for INR self testing?

Self testing may be suitable for you if:

  • you have shown good compliance with previous anticoagulation management;
  • you have the manual and visual dexterity to perform testing or have a committed support person to assist you with testing;
  • the clinic or physician’s office following you has a policy that approves patient use of the instrument;
  • you and your healthcare provider agree upon a method of communication regarding the INR results that  you will obtain.

Appropriate training and consistent quality control of the instrument are key for INR self monitoring to be safe and effective for you.

What INR home monitoring instruments are on the market?

Two instruments are being marketed in North America (table 1). Either is a good option for patient self testing. The instruments are small and light, weighing only between 5.3 and 28.8 ounces. For  INR testing, only a small amount of blood needs to be applied to a test strip (for CoaguChek®XS and INRatio®), only one small to large blood drop. Prices for the machines are roughly between $1,500 and $2,500, and prices for one test strip, i.e. for one INR test, $7.00 –  $18.00.

When trying to decide which of these instruments to purchase, you may want to consider:

  • your physician’s or anticoagulation clinic personnel’s recommendation, based on their experience and knowledge of the instruments;
  • other patients experience and satisfaction with (a) their home monitoring device, and (b) the educational and support services provided to them by the manufacturer and/or distributor (IDTF); support and education services provided by the company making the instrument or distributing it;
  • amount of blood needed for the test strip (10 micro liter for CoaguChek®XS; 15 micro liter for INRatio);
  • ease of operating the instrument;
  • Weight of the instrument may matter to you especially if travelling frequently.

Do INR home monitoring instruments give reliable INRs?

Yes. INR values obtained with finger stick home monitoring devices are typically very well reproducible and correlate well with INR determinations obtained from blood sticks from a vein and tested in a laboratory. However, INRs above 4.0, discrepancies to INR values obtained with other test methods may exist. This is a general limitation of the INR and not unique to the home monitors. It is not clear which of such discrepant values is more reliable and accurate: the INR determined in the laboratory or the POC instrument INR.

INRs from POC instruments are unreliable in about 1/3rd of patients with the clotting disorder called antiphospholipid antibody syndrome (APLA syndrome) who are on warfarin. In these patients, the POC devices give INR readings that are too high, or the instruments report error messages. This is the case with the 2 instruments on the market. If you have APLA syndrome, your INRs should be checked=”checked” from blood drawn from a vein and tested in a laboratory. That value can then be compared to the INR obtained with a POC instrument from a finger stick. Only if both values correlate well may it be acceptable for you to use the POC machine for self testing.

Do insurance companies pay for home monitoring instruments?

Medicare covers home patient self INR monitoring  for chronic, oral anticoagulation management for patients with mechanical heart valves, chronic atrial fibrillation, or venous thromboembolism (inclusive of deep venous thrombosis, DVT, and pulmonary embolism, PR) on warfarin.

The monitor and the home testing must be prescribed by a treating physician and all of the following requirements must be met:

  • The patient must have been anticoagulated for at least 3 months prior to use of the home INR device; and,
  • The patient must undergo a face to face educational program on anticoagulation management, and demonstrate the correct use of the device prior to its use in the home; and,
  • The patient correctly uses the device in the context of the management of the anticoagulation therapy following the initiation of home monitoring; and,
  • The patient should not perform self-testing with the device more than once a week.
In Ratio Testing Machine INR CoaguChek XS INR Testing Machine
InRatio® CoaguChek® XS

Other insurance carriers usually follow Medicare’s lead when it comes to coverage decisions. Some companies pay for  them upon submission of the first insurance claim; others may initially deny payment but later agree to pay, if you are persistent and explanatory letters are written (by you and/or your healthcare provider) and phone calls made.

How do I get an instrument?

If you are interested in having one of these home monitoring devices you should discuss this with your anticoagulation provider. Your physician needs to be supportive because he/she:

  • will need to write a prescription for it;
  • will need to be available for the continued oral warfarin dose adjustment;
  • is medically responsible for your anticoagulation management.

Once a prescription has been written you can contact one of the companies that can help you obtain an instrument (table 2). They are called independent diagnostic testing facilities” (IDTFs) and are specialized in:

  • checking with the insurance companies whether they will pay for the instrument and testing materials;
  • filling out the necessary insurance paperwork for you;
  • providing you with the instrument and testing materials;
  • teaching you how to use it;
  • be available to you in the future for answering any questions or assisting you if problems with the testing device arise;
  • Some of the IDTFs also have software and methods to help track your INR results and communicate the results to your healthcare provider.

Table 1 FDA Approved INR Home Monitoring Devices

Name of Instrument Company Website Phone Number
CoaguChek® XS Roche 800-852-8766
INRatio® HemoSense 877-436-6444
What can I tell my healthcare provider if I am interested in INR self testing?
Your healthcare provider may be hesitant for you to use an INR home monitoring instrument. He/she may feel left with the work and hassle of phone calls dealing with INRs that have been tested by
you at home, giving medical recommendations over the phone, but not receiving appropriate reimbursement for these services. This is a valid concern if you are on an oral anticoagulant for reasons
other than a mechanical heart valve and your insurance is through Medicare/Medicaid. However, some other insurance carriers have started to cover such services, even if you are on a warfarin for DVT,
PE, irregular heart beat and other reasons. CMS is also presently discussing to expand coverage of home INR testing to indications other than heart valve replacement. A decision is expected early in
2008. At this point, it is probably best for you to:
  • discuss your interest in using a home monitor with your healthcare provider;
  • talk to your insurance provider and inquire about their approach to coverage for the instrument, the testing materials (strips or cuvettes) and the healthcare provider’s services.
  • The easiest route may, however, be to utilize the experience of the IDTFs to help you and your physician navigate the reimbursement issues.



1. Heneghan C et al. Self-monitoring of oral anticoagulation: a systematic review and meta-analysis. Lancet 2006;367(9508):404-411
2. Yang DT et al. Home Prothrombin Time Monitoring: A Literature Analysis. Am J Hematol 2004;77:177-186.
3. Dorfman DM et al. Point-of-care (POC) versus central laboratory instrumentation for monitoring oral anticoagulation. Vascular Medicine 2005;10:23-27.
4. Gardiner C et al. Patient self-testing is a reliable and acceptable alternative to laboratory INR monitoring. Br J Haematol. 2005;128:242-7.
5. Perry SL et al. Point-of-care testing of the international normalized ratio in patients with antiphospholipid antibodies. Thromb Haemost. 2005 Dec;94(6):1196-202.
  • CMS – Centers for Medicare and Medicaid Services
  • DTF – independent diagnostic testing facility
  • INR – International Normalized Ratio
  • i.v. – intravenous
  • POC device – point of care device
  • PST – patient self testing

Originally posted October 15, 2008

Click here to return to our news page.


Author: admin

21 Responses to "INR Self Testing"

  1. Brian Jones
    Brian Jones Posted on August 28, 2013 at 1:27 pm

    i have been registering 2-3 on the INR scale since I began having the blood test in January 2-13. The latest reading showed 1-6 and my dosage of Warfarin as been increased by 25 per cent…. when I enquired why the reading had changed after being stable since Jan.i was informed that it maybe to do with the food I am eating or the excercise I am taking. This poor information is giving me cause for worry.

  2. Edith
    Edith Posted on September 27, 2013 at 10:07 pm

    I have been on coumadin for 6 years. I test every month at doctor office or hospital lab. If I have to take antibiotics or other meds, I have to test sooner. I my levels go too high or low, I have to test sooner. I asked for a home tester but my MD didn’t feel they were reliable. I’m getting tired of going to office to get labs, wait one day, and hope the office calls me with results. Last month, I got Shingles. Two meds for that. Doctor said test PT/INR on Wednesday. I failed to do so. Friday night, major abscessed tooth. Lots of Advil. Sunday night, abscess so bad that I go to ER, but change my mind and go home. Call MD, he calls in Antibiotic. Monday AM. Go to dentist. He sends me to Oral Surgeon. But 1st I stop by my doctor’s office. He says to go to hospital and get PT/INR stat and have them call his cell with results and he will drop my range to have oral surgery. I go to hospital, get PT/INR. Doctor calls and says my reading is 7 and I have to be admitted immediately. If i could self test, this may have been prevented. I had to wait another day for the oral surgery and all the while the infection continued to fill the side of my face and proceeded down my neck. Four days after tooth removed and still have infection draining and a very sore knot on the side of my chin. Grrrr. I wish i didn’t have to take Coumadin but I’m on it for life (2 stints due to DVT (May-Thurner Syndrome).

  3. Al Smith
    Al Smith Posted on October 4, 2013 at 11:05 pm

    I have had a very challenging time finding a medical supply co. in NC that sells the roche coagucheck INR device. Does anyone know suppliers in this state who sell these devices?
    I know this is a very long shot, but any help would be greatly appreciated…

    • S Harper
      S Harper Posted on October 19, 2013 at 3:21 am

      mr al smith try looking for a Lincare Company somewhere in your area I work for Lincare and we provide the home inr testing — in our area

    • candy
      candy Posted on January 7, 2015 at 10:04 pm

      My daughter also takes warfarin, Walgreens Drug Store Pharamist gave her the name of a company in California who sent us the entire system, and they have never charged her. its been great testing at home, instead of the weekly trips for inr test at hospital. I hope this helps

      • mercedes
        mercedes Posted on January 20, 2015 at 1:05 am

        Hello my name is Mercedes. I’m a Coumadin patient with a mechanical valve in my heart. And have taken this medication for 16 years. With many hospitalizations for heart failure and belly injections. I am in need of an inr machine but can’t get any companies to help. Single mother here and really desperate. Can you remember the name of the company that your daughter contacted? It would help me so very much, just needing a little hope. My Email is thank you so much!!!!

      • Wendy
        Wendy Posted on October 29, 2015 at 6:37 pm

        I’m interested in getting one for my mother in law. Is there anyway you could give me some information? Thanks 🙂

  4. fred venter
    fred venter Posted on October 11, 2013 at 9:28 pm

    I have been on Warfarin for 26yrs, having had 11 dvt’s…had stenting done a month ago, but still developed yet another clot in the left leg. I increased my Warfarin intake to 15mg per day and suddenly landed with an INR count of 9.1, bleeding through. Blue bruises appeared and a intense keep my INR at a level of between 3 and 4, what should my intake be?

  5. admin
    admin Posted on November 20, 2013 at 8:01 pm

    Thank you Debbie. It is now updated.

  6. Dick
    Dick Posted on December 11, 2013 at 12:18 am

    Ihave been usingg a coaguchek xs for a while and warfarin dosage is consistent. Dr now wants test only about every 3 weeks. Equip provider requires weekly testing or will recall the equipment. Any suggestions ?

  7. Deborah barge
    Deborah barge Posted on February 2, 2014 at 7:54 am


  8. Angé
    Angé Posted on March 20, 2014 at 6:37 am

    I check my dad’s weekly and pay attention to his diet, any new medications, and signs of internal bleeding. Since I also check his blood sugar, I pay attention to the viscosity when I draw his blood. Any sign indicating it’s too thin has me take a look into his INR as well. Some signs that clue me into his blood being too thin are confusion, blood in his urine or stool, blood too free flowing when I check his glucose level, sleeping for long periods of time.

  9. Juanita
    Juanita Posted on June 24, 2014 at 5:28 pm

    I had a DVY in 2006 ..I’ve got a green field filter in I’m on 7 mgs of warifin a day I have to have it checked 2 or 3 times a month…I have there any hope of me getting a home pt/into Macy me for home. Thanks u

  10. Kent
    Kent Posted on August 12, 2014 at 5:40 pm

    I got set up with home INR testing through Advanced Cardio Services over 2 years ago after going to the clinic for 5 years of INR tests. I tell you what, I couldn’t be happier! I have the CoaguChek XS meter and I know if I am in or out of range every week and can adjust my diet or coumadin accordingly. I travel with my wife and we never have to stop to find a hospital or lab to have my INR tested. It is as easy as testing my blood sugar and I can’t believe more people don’t do it. I don’t pay a thing for my INR testing or spend money on gas getting to the clinic and I’m feeling great!

  11. peter g mudry
    peter g mudry Posted on October 6, 2014 at 4:26 am

    will medicare pay for pt testing equipment it is the only insurance i have.i am 68 years old and have had 2 episodes of pe nearly died 2 times.medicare will pay for test at doctors ofice which is almost a one hour drive from my home. i have a heart condition with sevear neck & back problems! i am totatly disabled & live alone my wife died of lung cancer one year ago. thank you peter ..

  12. David
    David Posted on October 7, 2014 at 7:56 pm

    Yes, Medicare will cover based on this criteria. This is from the CMS website.

    “For services furnished on or after March 19, 2008, Medicare will cover for the use of home PT/INR monitoring for chronic, oral anticoagulation management for patients with mechanical heart valves , chronic atrial fibrillation, or venous thromboembolism (inclusive of deep venous thrombosis and pulmonary embolism) on warfarin. The monitor and the home testing must be prescribed by a treating physician as provided at 42 CFR 410.32(a), and all of the following requirements must be met:
    The patient must have been anticoagulated for at least 3 months prior to use of the home INR device; and,
    The patient must undergo a face-to-face educational program on anticoagulation management and must have demonstrated the correct use of the device prior to its use in the home; and,
    The patient continues to correctly use the device in the context of the management of the anticoagulation therapy following the initiation of home monitoring; and,
    Self-testing with the device should not occur more frequently than once a week.

  13. Curtis Dollar
    Curtis Dollar Posted on November 2, 2014 at 4:17 am

    I have a blood clotting disorder, Prothrombin gene mutation G20210A. I’ve had a stroke, DVT, and P.E at the age of 29. I’ve been on anticoagulants for nearly 2 years, and am a great candidate, and very responsive to the coumadin treatment. My INR’s seem to change twice a year, winter and spring. I’ve recently got a new lab pharmaceutical doc for my INR’s, I don’t like her much. She’s changed everything and I think, because of my track history, I should be able to do my own INR’s. I’m going to run it my primary Dr.

  14. Bill Topper
    Bill Topper Posted on February 4, 2015 at 7:47 pm

    I am hypercoagulative, a diagnosis following a nearly fatal PE. I was put on warfarin to thin the blood. I still had emergency hospital trips for both bleeding and clotting. I had an INR of 2.9 when I went to the emergency room for a DVT. Thed doctors were completely confused by this scenerio. I ask for a prescription for self testing and was told that legal council had advised against doctors prescribing these devices. Wow, I am so glad that our legal counterparts are so interested in my health problems. The solution came via the “black market” through the internet (in Germany the equipment and warfarin is available over the counter). I found that monitoring INR 2 to 3 times a week provided me with a very interesting outcome. My fluctuations were 1.6 to 4.4 while staying at the prescribed Rx dosage level. When the official clinic test resulted in dosages level changes I would follow the order and noticed that the effects of these changes took 6 days, meanwhile my INR often continued to climb/ sink often putting me into the non-theropedic range. I took notice to the influenve of vitamin K on the INR level and found that when my INR was falling dangeriously low (below 2.0) 6 oz of red wine would move it to 3.0 within several hours, and when it would be approaching 4.0 a generous helping of high vitamin K whould have it back within theropudic range the nect day. No changes in warfarin was needed and 9 months w/o emergency room visits. My ultimate reward, I was put on Zarelto. Now I have no way of monitoring my problem, but have recently experienced clots being caught in my foot and I have a titanium filtern in my chest. Now all I need to worry about is my unprotected brain.

    I really have to respectfully disagree with a general statement like “Self testing with the device should not occur more frequantly than once a week (David post 10/7/14). With a 6 day lag on the impact of a warfarin dose change, one can easly spend several days of a higher or lower INR excursion. My experience shows the frequancy really needs to be set for each indivual patient since factors like metabolism and eating habits factor into the chemistry of the body. In see this being similar to a diabetic patient monitoring blood sugar, to avoid insulan shock. With warfarin you really have to have a doctor deteremin your therapudic level, do not make any changes to this dosage (unless your doctor requests one), and use your diet for a next day correction. I would actually do a next day check to assure that my INR is correcting. If the condition was still trending negatively I would call my Hemotologist (This action never was needed). This presents no more of a risk than monthly testing at rhe clinic and provides for detecting a potentially leathal condition. Note that I was well received by my doctors regarding my activity. None of them would give me a prescription for the tester or strips, but they would sometimes ask me about my latest readings. I was using an INRatio tester (the professional model which was about $800 and $200 for 50 test strips; for some reason the patient models cost about twice that amount). I ultimately received a phony test strip recall from the US branch of the company, but told them that I was only using the strips to control my diet not my warfin dose level so there was no chance of a misdosage if they were defective.

    p.s. My selt test INR readings were always within .1 of the clinic results (I would use the hospital blood draw lab). Instead of being “shuned” by the AMA the self testing should be manditory, warfarin can work very well but is being administered wrong in the US. The FDA really needs to wake up on this issue. I have seen 1 neighbor die from a PE while taking warfarin because we are not allowing science to help us. ( I am a retired engineer/scientest who worked in a advanced development lab during part of my career).

  15. don ross
    don ross Posted on June 3, 2015 at 12:32 pm

    Where can I purchase an inr tester I live in western australia .can anyone help. Thanks from don.

  16. Jan Bragwell
    Jan Bragwell Posted on August 17, 2016 at 6:46 pm

    I have been on Coumadin about 12 years & have going to clinic for INR testing. I am getting older ‘ need to test at home. Please call me at .

    • L F
      L F Posted on August 24, 2016 at 7:31 pm

      Hi Jan…

      You should talk to your doctor about the option of having your INR tested at home or testing it yourself. Your doctor should be able to help you explore options that fit your needs best.