Warfarin again: Hi everybody, It is me... - British Heart Fou...

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Warfarin again

Hi everybody,

It is me again and my warfarin dosage

I am taking it following my mitral valve replacement

Despite being now on 12mg daily my INR is going down rather than up.

I am still trying to be on the desired range and I am aware of the influence of vitamin k.

Yesterday it went again to 1.8 and on Friday was 2.6.

I am starting to have the feeling that warfarin doesn't work for me.

Did anyone in the group experienced the same?

Is there a maximum dosage?

My surgeon was saying that 11mg is quite high and I am.now on 12mg.

Thank you in advance for your help


29 Replies

Hi Hon

I’ve taken warfarin for 20 years (for a different thing) it’s a fickle thing and have noticed that anything and nothing can effect your INR. Weather,stress, new drugs , change in routine etc

VitK does affect your INR so be consistent in your intake, for example I have broccoli every Sunday, so same amount week in week out.

Also try and get your INR done at the same time, also is it being tested in the same way, venous sample or coagucheck machine. The half life of Warfarin is roughly 3 days I know some test daily as I do when my INR is high but really there doesn’t seem any validity in such frequent testing. But take advise from your anti-coagulation clinic. I do know people who take 22-23mg of warfarin a day.

Hope it all gets sorted soon


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Thank you Judes

I guess it is only the beginning for me and that's why I am so concerned.

But it is good to hear other people experience, I am finding comforting.

Wow, I didn't imagine doses can go as high as 22mg!

Hopefully it will get sorted soon

Thank you again x



I have a metallic Mitral valve, installed in 1993. I have been self-dosing since I left hospital and have had many problems to overcome. In biology, swings are normal, whatever you do. I actually care little about diet. I will binge on some brussel sprouts (yummy). I eat fruit and vegetables that are seasonal, so some weeks I have loads, and some weeks almost none. Gut bacteria produce most of our Vitamin K, so I discount food as a major factor.

Basically, I accept a wide range, because my experience is that from one week to the next I can swing from say 2.2 to 4.4, then without changing the dosage and without changing my diet, the next figures are in range. In other words, I accept that in some people, a wide range is normal.

I try to stay between 2.0 and 5.0 as my absolute limits, and 2.5 to 4.5 as normal. For most people this is not dangerous.

At the beginning, it takes a while to settle down to a stable dose. Also, take greater care with friction in your hands. I do a lot of DIY and experienced minor bruising in the first year that never returned later.

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Thank Lowefor sharing your experience.

I am vegeterian and what you are saying is really helpful.

I think I am too careful and it doesn't pay off anyway as the INR seems to have his own mind.

With this new type of mitral valve that they installed the range is from 2.5 and 3.5.

Mine is never too high, the highest is ever been was 2.6 and it was because I took amoxcillin for dentist appointment

It is normally beteween 1.8 and 2.2

The surgeon advised that I should be around 3 ideally and that's why I am a little worried.

At the clinic I have been assigned are giving me injections every time my range is below 2.

I guess I will follow your advice and starts to eat what I like as it seems food has very little to do with it


There seem to be different opinions for the type of valve and recommended range. Even within the same hospital before discharge I was getting that! No one ever seems to factor in the way that minor bruising is more likely the first year. In the long term, I aim to be over 3 and less than 5.

I was interested to read that you are given injections every time you go below 2.0. That is very re-assuring. I as a self doser have recently come to the same conclusion and I should ask for that for myself when I need it! The reason is that, from my reading of the literature, the real clot protection kicks in at around 2.0. Put it the other way. Protection against clots decreases sharply once you go lower than 2.

What most people do not know, but I can document, is that there is considerable variation in the venous blood testing. For convenience take the variation to be 10%. Which means a result of 2.0 could be 1.8, and you really should be over 2.3 to avoid these margins of error in venous blood testing.

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You are spot on

In the warfarin clinic I am going, they have also told me about the 10% margin.

Yes, I guess everyone on warfarinshould have some clexane handy for emergency


Good to hear the 10% is known about, because this information has yet to be applied to the decision making algorithms/flow diagrams that I have seen. I like margin. So I agree with the doctors who have said I should be above 3 most of the time. And while I can take my time for nature to self-correct with a result more than 4, I cannot take the risk with anything less than 2.5 because 2.5 could be 2.2 and a lower level puts me in danger.

So, what I do is boost. A few days ago I had 2.3, so, I boosted the reservoir by taking a small supplement for two days, then returned to normal dose. My reasoning is that most problems are to do with changing the reservoir, not changing the dose. I have explained this in my article Lowe I. 2017. Warfarin self-dosing, a case study on long term self-management of anticoagulation. Journal of Observation Pain Medicine Vol 6 pp 31-40. joopm.com

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Thank you so much

I will look into your article for sure .

Amazing that you can self dose, it is because you are a doctor or because of many years of experience with this particular medication?


No, I am not a doctor, though I did do a B.Sc in Human Biology, which included dissection of a cadavre:) . Over on the AF forum you will find that many people are self-dosing. Frankly, it is no more difficult than managing diabetes. In theory you need training. I was given two minutes, while in hospital. I was provided with the analogy of a paintbrush which is charged with paint, loses it, and regularly topped up. From DIY I understood perfectly. I was reminded that any dose change takes 2-3 days to have effect. That was it.

Over the years I picked up the odd tip or two, and principles, and went on to develop my own thinking and enrich it with reading the research articles, and, in learning from how others do it in the forums.

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Amazing, I hope one day I will have the confidence of self dosing as well.

I do trust my level of intuition that mixed up with a bit of experience and common sense could lead me in the same direction

I need to buy the machine first 😉

I will as soon as I get a little bit of consistency with my INR

At the moment Ithey are still asking me to go the clinic twice per week.


One of the main benefits of self-testing and self-dosing is the time saving. If you buy your own machine, you should be able to get the test strips on prescription. Most people have to see someone, say, once a year, to review and discuss. At the beginning you might want to agree something like, if more than xx or less than yy I will phone for advice. But if you follow the advice of the article below, which I really like and has a lot more authority than my article, so you can quote it to your doctor, you will not go far wrong.

Kim YK, Nieuwlaat R. Connolly SJ, Schulman S, Meijer K, Raju N, Kaatz S. and Eikelboom JW. 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 vol 8: p101-106

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Thank you for the precious reccomandation

This is why this forum is unbelievably helpful.


I've been on warfarin for nearly 7 years, my range tends to be 2.5 -3, but it can vary, very seldom goes higher, but does go lower, I tend to not think about what I'm eating too much, I also like a drink, I don't tend to drink in the week but will probably have a bottle or so over the weekend ( wine or prosecco) I used to drink daily only a glass or two, and my nurse always used to say as long as your consistent it will be fine.

Speak to your nurse or clinic there maybe something in your diet that is causing it?

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They seems to think that because I am vegeterian I might need an higher dose.

But with the higher dose it went lower

It is a bizarre medication but unfortunately so important.


If you are a vegetarian you are eating more vitamin K than most of us folks. The key, I believe, is to eat what you want but be consistent with what you eat/drink every week. With that in mind I think your INR dosage will likely stablelize.

As some mention INRs will be affected by antibiotics, supplements you may add to your regime and any change in diet.

It’s can be frustrating but keeping a log of what you put into your body will better help understand the triggers that bounce your INR up and down.

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Hi and thank you for your help.

I eat more or less the same things and I avoided broccoli, spinach etc and all the veggies high in vitamin K as I am conscious of the fact that by being vegeterian I am eating an higher level of vitamin k than anybody else

I never drink alcohol so this is something that couldn't possibly effect it.

I am seriously having such boring diet and eat more or less the same things ...that's why I am thinking to eat more greens as it doesn't seem to make a big difference.

When I was on 11mg I had an higher INR than when I am on 12mg

That s why I started to think.that I am sort of immune to warfarin...


I have been to a couple of talks on heart medication. One factor that apparently affects doseage of drugs like aspirin and warfarin is weight. The nearer you are to ideal the better and yo-yo weight can make doseage requirements erratic. He said things became particularly difficult with drugs in general for those over 20 stone. Obviously it may well not be relevant but I think it is worth pointing out for the benefit of other readers.

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Hi Micheal,

Very interesting...I didn't know that.

I wonder if this applies for people slightly under weight

I have never been big but after my surgery I lost over 10kg


There are indications it does' This is from The Lancet: thelancet.com/journals/lanc...

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Very interesting, thank you for sharing


Thanks. The article refers to antibiotics and is quite old (2009). Not tonight, but soon, I need to go to google scholar, paste in the reference, and see if any more modern articles have developed this idea (using the 'cited by' option). Potentially very useful trail. I often ask doctors to treat me like a teenager for drug doses, because my natural weight is one of the lowest for my size.


I've been taking warfarin for several years and it's probably the thing i do best. Recently after antibiotics it dipped to 1.9 so i thought I'd up my greens a lot. Straight back to 2.4, 3mg. Is it because I've been taking them for several years? It used to be more variable. I'm not vegetarian but eat very little meat but quite a bit of fish

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Thank you for sharing your experience

I was under the impression that dark greens are making the inr lower due to the high content in vitamin k and in my case, antibiotics are bringing it up.

I suppose everybody reacts differently and that's why it is so unpredictable


Yes, people do react differently, which is why I am against the rigid use of decision charts. Self-dosers get to know themselves and adjust their decisions. Even non-self-dosers can keep track of their history, remind the decision taker, and ask them to take into account your history.

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Thank you for your advises.

With this in mind I will start to eat all the greens and observe the reaction on my body.

I avoided food high in vitamin k up until now thinking that they would lower my INR even further but probably all I needed is a nice portion of spinach every week 😉


OK. If you eat loads of greens, eat them regularly. Try to avoid binging, and try to eat 'very roughly' the same amounts each day. For many people, this greatly improves their stability.

Personally, l live for a few more weeks in a Mediterranean city, which means seasonal food, and gaps between the seasons when there is very little greens around. I have not noticed a difference. But a lot of people do notice it, so it is best to follow the consensus to be consistent.

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I will try this way and see how the whole things work out.

I think I have learnt something good....I really need to get to know my body and the interaction it has with warfarin and the only way I can do it is by experiments.

It would be much easier to have these foods on my diet than not to have them..

I am vegeterian so it was a big effort from me to give up ...I absolutely love sprouts, broccoli and spinach


I love sprouts too. Even the smell of them cooking attracts me, and I really wish the deodorant manufacturers would produce one with this very pleasant smell:) Since you are a vegetarian, you are more likely than others to be consistent. All the best.

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Thank you so much for all the good advises and encouragement....

On a side note, I know what you mean about the sprouts smell, they do have a lovely smell and taste , not too sure I would go as far as a deodorant but they are amazingly good.

I even like them row 😃


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