Warfarin self-doser experience

[ILowe]

This post is for those who take warfarin, and in addition to doing their own testing they also decide on their own dose.

I have been taking warfarin, and deciding my own dose, for over 28 years. I had a series of temporary contracts abroad. I became used to self-management, so when I took early retirement I was understandably nervous about submitting to a doctor/nurse who would want to tell me what to do. Well, somehow, I managed to negotiate with my GP that they would continue to prescribe warfarin and I would pay for the test-strips myself, and if there were any problems I should not hesitate to come in and get my INR checked. Later, I learned that in Wales, the responsibility for the INR is nowadays in primary care, not hospital. Except when in hospital.

I was in hospital recently. Anticipating problems I went prepared with a few research articles, and a photocopy of my INRs for the last year. There was no way I was going to let them handle (and perhaps lose) my "Yellow Book" of data.

When asked what my daily dose was, I said, 5.25mg. This figure attracted attention and I had a series of visits. And you had to be ready at any time, since they came unpredictably and at odd hours. They said the figure was impossible. How did I get 0.25mg? That was easy. My GP supplies 0.5mg tablets which I break in half. And for years I have been breaking existing tablets of 1, 3, and 5mg into quarters. The slight difference in shapes averages out over four days. Then they questioned if 0.25mg made a difference. Here I had to be careful. I said that for some patients it probably is too small a difference, but I have a history where that is very important. I can prove that 5mg is too low and 5.5mg is too high. Some of the doctors did not believe me.

The doctors then made a series of what I would call "mistakes".

1/ They tested the INR daily, and wanted to make dose adjustments daily, which came on top of them trying out new medicines and doses over several days.

2/ Dose changes were large

3/ The dosing doctor would change. This is very important: in dosing you want consistency of decision making. This was not too bad when they came to see me and discussed the evening dose with me. In this case I had to adapt all my bargaining skills learned abroad and apply them in a British hospital.

But sometimes the dose was given as an edict and announced by a nurse. No negotiation was possible! One evening I phoned my wife about the dose. What do I do? The edict-dose is obviously wrong and if repeated for three days will push my INR over 5 !! She said, you will be leaving in two days, so do as they say, and correct the damage when you get home. Wise words. The alternatives were to fudge it, or for me to overrule and explain later.

There was also a lot of discussion about self-dosing. Some had never heard of it, or never met a self-doser. Some tried to quiz me and see if I really knew what I was doing. I tried to stay polite, and stay in teacher mode, open to new ideas. I asked them to give me research articles, and provided a few of my own. In particular, I said that I followed the research so I was NOT independent. I follow an enhanced version of Kim et al Effect of a simple two-step warfarin dosing algorithm on anticoagulant control as measured by time in therapeutic range: a pilot study. Journal of Thrombosis and Haemostasis. 2010 Jan;8(1):101-6.

[P0rtnahapp1e]

Nothing to do with warfarin 😀. Are your roots in Northern Ireland?

[Bagrat]

My friend had a similar problem. when her husband had surgery. Been on warfarin for years since valve replacement. Was prescribed tiny dose after surgery instead of his normal dose then when little was changing re INR, prescribed twice his normal daily over weekend ( home by then) which wife knew would send it far too high, so she did what she thought fit, which was perfect.The trouble with what "the software" says it only seems to reflect that days blood test. We have great care assistants at our surgery who if it looks iffy seek out a GP to say yes to their take on it, which is usually right.

[ILowe in reply to Bagrat]

Unfortunately it seems that the software and the instruction charts (with a few exceptions??) only look at one result. Yet, a golden rule in medicine is a good case history. That is why I like the advice of Kim et al to wait until you get two or more out of range results before acting, unless you are severely out. With this reference I have a well-cited article which should have some authority which I can use as backing.

Also, we must never forget that some people respond dramatically to a small dose change, and others do not. Has the software been 'trained' for each individual, to take this into account? I doubt it. I could be wrong, but I have not seen reports of warfarin dosing software based on neural learning.

[Bagrat in reply to ILowe]

My husband is on warfarin and NOTHING seems to provoke a change in his INR. We are not particularly careful about diet and or vit K. I force greens down him bacause they are in my opinion a good way of reducing minor fluctuations in diet causing a problem and it seems to work. I onthe other hand, abandoned warfarin for apixaban as any change in anything caused fluctuations so agree totally.

[ILowe in reply to Bagrat]

I have often puzzled about what you say. Did you know that Vitamin K is made by microbes in the gut? Those who make a lot will be more stable and can tolerate (buffer) more changes in diet.

I am self dosing so can do what I want, or, in my case, do nothing if I want to. I have established that my natural variation is over 2.0 INR. [Lowe, I. Warfarin self-dosing, a case study on long term management of anticoagulation. Journal of Observational Pain Medicine – Volume 1, Number 6 (2017) 30-38.]

Unlike most doctors, I have accepted and bowed to nature, and I do not try to force a tight range and will accept any INR between 2.5 and 5.0 without jumping to a dose change. When you do that, suddenly, the fluctuations are less important and tend to self-correct.

One major reason for fluctuations is over-correction. [Meier, DJ. Seva, S. and Fay, WP. A comparison of anticoagulation results of patients managed with narrow vs. standard international normalized ratio target ranges. J Thromb Haemost 2007: 5: 1332-4.]

[Bagrat in reply to ILowe]

No didn't know where vit K was made. I'm very interested in the gut microbiome and include fermented foods and other encouragements for friendly bacteria! My husband not so much!!! Wonder if gut transit times have any bearing mine fast husband's very slow!! Isn't the human body fascinating.Most doctors never give anything time. They seem to find it hard to do nothing or wait and see. Last year I felt unwell a lot. Only one doctor made sense. He said " sometimes we just have to wait until the picture becomes clearer". Wish more of them would.

[ILowe in reply to Bagrat]

"gut transit times". Now that is a new and interesting idea, and measurable in various ways, from uncrunched peanuts to more sophisticated. Thanks. I will look into that. I also have the impression that some medicines make me more stable. The most stable INR I ever had was when I was put on the dreaded Amiodarone for a few weeks.

🙂

[Bagrat in reply to ILowe]

joinzoe.com/bluepoop you may find this of interest then. Theresa recipe somewhere formaking your own blue cupcakes for the test!!

[ILowe in reply to Bagrat]

Thanks for the link. I shall investigate. Is high speed throughput associated with instability?

Overnight I got to thinking. Many married couples exist where both are taking warfarin. They are both taking similar diet, but as you say, one can be stable and the other unstable. We are often told that diet is an important part of warfarin control. Surely someone has done some research on such couples?

I actually think that many of the people labelled "unstable" could be stable, if the range is broadened. The instability comes from forcing a narrow range.

[baba]

Well done on your diplomacy.

[irene75359]

My practice nurse was appalled when I told her I tested every 10 days (she said that was far too often) and also at the fact that I took vitamin K2 every day. I would chart my INR and if I saw an upward or downward trajectory over 9 or 10 weeks I made a tiny adjustment (once) of about .50mg. I had to go in armed with proof of my methods to see one of the doctors who fortunately was quite enlightened and said he wasn't going to interfere with what I was doing as I was in range all the time bar illness. I was changed onto Apixaban when COVID started as a trial but stayed on it as recent health problems has made that a better option for me now. But for a few years I was more than happy with warfarin and self-regulation.

[ILowe in reply to irene75359]

Irene, you touched on an important issue: control. Somehow many medics are afraid here, even though they will, when pushed, agree it is no more difficult than diabetes, and they let patients control their own diabetes. Somehow it must always be a medic who decides.

[MarkS]

Your story does show up some of the shortcomings of the NHS, such as no examination of history and doctors and nurses thinking they know best.

I recently had a colonoscopy and had to have blood tests for kidney function, etc 4 days before. I went in for the colonoscopy and a nurse came over and said my INR was too high at 2.5. I had to explain carefully that I had only stopped warfarin the previous evening and that I self-test and it is now down to 1. They also said to restart my normal dose that evening. In fact I doubled the dose for 3 days and on the 3rd day was up to 2.0, otherwise it would have taken ages. Having said all that, the colonoscopy was very efficient though quite a bit more painful than I expected (the bend to the sigmoid bit was quite tight).

At the surgery they think it's great I'm on warfarin as it save the NHS so much money.

[ILowe in reply to MarkS]

I am surprised they did not put you on heparin until the INR was back in range, either the heparin bridge with all its problems, or the heparin jabs you can self administer at home.

[ILowe]

Hot press. Several Research Papers have been published this month that support home testing and self-dosing. Knowledge is power. Before I pick a fight I need to know I have strong support. Here is a gem quote to use. The paper is open-access.

"Patient self-management (PSM), in which patients interpret the INR and adjust their own warfarin dose, has also been shown to improve INR stability and decrease the risk of thromboembolic complications and mortality and is recommended by evidence-based guidelines [10,11]."

Feasibility study of the Fearon Algorithm in anticoagulation service guided warfarin management. sciencedirect.com/science/a...

[BobD Volunteer]

I note frm my yellow book that in gteh last years since I started self testing my INR has been far more stable than ever. The algorhythms used by my surgery do not take account of trends so one yo yos back and forth ad nauseum. By ignoring any instruictions and doing my own thing I have been 100% in range (lowest 2.2 highest 3.0 ) I have a good understanding with my phlebotomist adn in fact she supplies me with strips wwehn needed. because I only test as requested or if meds have changed for any reason, a tin of strips will run out of date before I can use them up so I pop in to surgery and swap tin and chip for a new pack in good time for them to be used up in clinic. I have only used ten in the last year.

[ILowe in reply to BobD]

Once again it is the patient pushing the good medical practice and the patient working hard to do so without ruffling feathers. Apart from humans, there is only one algorithm I know of that takes account of trends... the Fearon Algorithm I mentioned, but, details of it are not published and so I wrote and asked for details, and I am not expecting them but I tried.

Several articles say an algorithm is better than humans. Perhaps only better than an unskilled human. When all my heart problems started nearly 30 years ago a cardiologist said to me, I must know my problem, and I must know it better than any doctor. The "expert patient" knows themself.

I liked the way you manage the test strips. I tend to use them up for more frequent testing, during self observation experiments.