AF Association
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Warfarin – a cautionary tale

Firstly may I apologise if this is long winded but I am not very good at summarising.

Like many of you I am on Warfarin. I have been taking it for the past 7 years although I had a previous period some 20+ years ago when I was also on the drug.

In a recent post the pros and cons of Warfarin and the various other anticoagulant drugs have been discussed by a number of us. As we are all acutely aware all drugs and particularly Warfarin should be treated with great care and taken strictly in accordance with the advice given by our doctors.

Warfarin like many other drugs, has issues with interaction with other drugs and foods and I have always been very aware of this. Warfarin can also make the work of doctors very difficult if you are careless enough as I was 9 months ago to cut an artery in my hand, or if any other illness is encountered.

The reason for my post is to share my recent experience following the ablation I had 3 weeks ago. As the procedure took six and a half hours and I was then required to remain horizontal for a number of hours afterwards it was agreed that I should have a urinary catheter inserted during the procedure while I was asleep. In any case my waste disposal system and hospitals have never got on too well. To my great relief I managed to negotiate removal of the catheter late that night when I was finally allowed to get out of bed.

All seemed to be well at first but as on previous occasions unfortunately I developed issues with my bladder with symptoms of cystitis. I hoped that it would settle down but when 4 days later it did not, I went to see my doctor for advice.

We both knew that normally a patient needs to take anti-inflammatory drugs and that also Cranberry juice was considered to be a very good thing to drink when experiencing these problems. We both also knew that Ibroprufen and Cranberries would influence the effectiveness of the Warfarin. We had a dilemma.

After much thought my doctor’s advice was that we need to deal with the cystitis, which by now was very painful, so he said to drink some Cranberry juice and also to take Ibroprufen once a day to reduce the inflammation of my bladder. I was to stop as soon as I felt it was having an effect. This I did after about 3 days. The remedy worked but in the end my discomfort lasted for 2 weeks in all before things settled down.

Over a week after stopping taking the Ibroprufen and the Cranberry juice I had my routine INR test on Monday and last night I received a telephone call from my GP surgery receptionist advising me that the test result was 4.1 - the target for me and normal results for me are between 2 & 3.

The revised Warfarin dose I was advised did not make sense to me as I was told not to take any Warfarin yesterday and to reduce my dose to 2mg one day and 3mg the next for 5 days and then to miss another day. I was told then to have another blood test. To further complicate matters I had already taken 3mg that day. The recommended dose did not make sense to me so I asked for a doctor to call me.

A doctor called me later and I explained my concern. The doctor looked at my results again and in consultation with my normal doctor they deduced that the computer had made a mistake and that the dosage I had been given was wrong. They advised me to keep on 3mg per day for 7 days and then to have a repeat INR blood test.

I was congratulated on spotting the error. I guess it is just lucky that I think about these things and do not blindly carry out instructions.

Some of you may have picked up on a post I wrote some weeks ago when I described how my sister in law, who was a closet alcoholic, died from a stroke last January following efforts by her hospital to reverse internal bleeding. She was on Warfarin and at the time her INR was recorded at 11.

The whole sad chain of events was avoidable as because of her drinking she missed two blood tests - she didn’t like morning appointments. We found out that she was also manipulating the dosage of Warfarin she was taking so that she, as she perceived could keep drinking.

The intention of my post is not to frighten anyone who has recently been prescribed Warfarin, it is a most effective drug and for many, including me, an essential as part of the management of AF.

Hopefully my post will illustrate from personal and family experiences how carefully the use of this drug must be managed.


15 Replies

Thanks you so much for that Pete. A good reminder to us all. I do agree that we need to keep our wits about us especially with INR testing and computer generated doses. We need to remember that the ladies doing these tests are not experts and in that age old adage "are just following orders. " Most of the programs fail to take trends into account I have found and will continue to prescribe the same dose even when a blind man could spot the graph racing towards one or other limit. In those cases one does need to request a second opinion so well done you.

So sad about your sister in law. My first wife was an alcoholic and I do know how secretive they an be so I doubt much could have been done for her in such circumstances.


I've been on Warfarin for probably almost 14 years. I bought a Coaguchek monitor 2/3 years ago so i self test. It's one of my best purchases even at £300.

I normally test weekly so that I don't get any nasty surprises from the lab. This must be the way forward for most of us.



Thanks for the information Sandra

Trouble is I have had enough of needles and once is enough for me.

Problem also as I see it is even if a self test was to throw up an odd reading it would still be necessary to get an official test done. As you will gather from my post I am not an advocate for adjusting medication without medical supervision.

Also for some it is too daunting to do self testing and also £300 is a lot of money for many.


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Actually the procedure in my area is that I email my results to my hospital clinic and I get instructions for my dose sent back to me that day.

If I can see ( from my own experience )that a tweak of 0.5mg either way will put things right then I do so.

I can see that self testing is not for everyone and £300 is a big outlay. There is/was some talk of certain health trusts trialling these monitors with patients.

I was having an average of 30 blood tests a year for my INR before I purchased the meter.


I realize it's easier to self-test in the US because financially the machine and supplies are handled differently. My coagucheck machine is onloan so it doesn't cost me out of pocket and my supplies are sent to me, covered by my insurance with a small copay on my part. irina1975


I agree . For the past several years I have self-tested and self-managed along with my coumadin nurse. I tested weekly so I could keep a tight control on my INR. Each week I would call in my result. If INR was fine (and fine for me was between 2.0-3.0-'extra-fine to me meant right in the middle) i continued my same dose. If the INR was slightly out of range together we would discuss dietary ways to pull the INR back to where it should be within the following week, We did NOT change the dose.(There were times I ate green veggies for breakfast rather than play with changing the dose.) My EP approved this approach and was always aware of my numbers. The only time I had 'dosage skirmishes' was when, on occasion, my coumadin nurse Lena was off and a nurse was filling in who didn't know me or our routines. she would want to follow the computer (all this was by phone from my home) and I would try to explain that this regimen has been working for 2 years, Lena would be back the next day, and let's not mess with the system. It usually ended by me saying I am going to continue with what I know had been working and she could chart that I was noncompliant or whatever she needed to do to cover herself. My agenda was to keep my INRs as stable as possible. This way of managing my coumadin worked fine, except for side effects that encouraged me to have the Watchman procedure. BTW if all goes well with my TEE/TOE on Feb 28th my last dose of Coumadin will be March 6th. I am tempted to take that last dose with a glass of champagne (LOL). I really hope the way of the future is for patients to get more involved in self INR testin g and on a weekly basis. I know it will be a battle on several fronts but I believe it's a safer way to monitor INRs and maintain constant, safe coumadin levels. irina1975

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Well that why we are fortunate round here in that the CCG runs the Anticoagulation with specialist nurses. It covers 4 hospitals and loads of GP practices. They are very goo at looking at trends. If we get any medicines added, changed or deleted then you ring up straight away and they will tell you if you need any change to dose and tweak. Often they will arrange a new blood test which may be 4 to 7 days.

Actually 3.6 is not high and many are on 3.5 as normal top (I am).

That change seems excessive since it is a drop from 21mg per week to 17mg which is 20%. Here max adjustment is 10%. Also they would have used 0.5mg tablets. Also when you stop cranberry it will drop quite quickly.


I have been on 23Mg per week for some months with a steady INR of around 2.5 so I knew that there was something wrong and being told to take no tablets on two days not make sense at all. The doctors had to delete the previous data on the computer to get a sensible daily dose. I think it is a cranky program they have got.

We have no specialist anticoagulation nurses in this area that I am aware of which going on what you have in your area is interesting particularly as my local hospital is one of the UK's centres of excellence for heart issues of all shapes and sizes with a 3 consultants just dealing with Arrhythmia.

What concerned me a little was that my INR was 1.1 higher than my top target measurement and yet I had not touched a drop of Cranberry juice for over a week nor had I taken any more Ibroprufen.

How those that are not capable of making their own judgments fair I do not know.

Anyway alls well that ends well.


Actually 4.1 isn't excessively high and after all NICE and Dental Association allow Dental work including extractions to be undertaken if INR is up to 4.0.

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pottypete 1 NEVER NEVER EVER drink cranberry jiuce while yoiu are on warfarin.!!!!!!!!!!!!!!!!!!!!


I was told In January 2015 by lead Anticoagulation nurse for the whole district that you should not drink cranberry juice when taking warfarin and that was the official guidance in the UK. He did say that one recent study run in the USA contradicted that (I'm guessing 2014 or 2013) but that I should wait and see what trend was and any new guidance.


PeterWh DO NOT drink cranberry juice with warfarin unless you want to very greatly increses your INR ( as in maybe dangerously high). coumadin nurse told me this (USA)


Hello Traveler65

As I mentioned before I am very aware of the interaction between Cranberries and Warfarin. I have been on Warfarin for many years.

I had no alternative on this occasion as I had acute Cystitis and I needed to stop this so consulted my doctor.

Incidentally the anti inflammatory drug Ibroprufen also interacts badly with Warfarin. In my case I had to both take Ibroprufen and drink the cranberry juice on a very temporary basis to alleviate my very painful symptom.

I was under medical supervision.

My original post was really to alert others who unlike you and I might be unaware that this can happen and that normally without medical supervision some drugs and Cranberries can interact badly with Warfarin.

Thanks for your concern but I am fine and I only drank some for a very short period to help solve my problem.


I have always avoided anything with Cranberries but, as I explained, I did it under medical supervision for a specific reason and very short term to aliviate very bad reaction to having a urinary catheter removed.


I agree with what you did.

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