AF Association

Is it a "no no " to adjust your Warfarin dose ?

I only have blood tests every 6weeks .In that time my INR varies quite a lot and I drop out of range. I bought a coaguchek machine and I now alter my dose by up to a maximum of 1mg for a day or two either way to stay between 2 and 3 . I've not discussed this with my surgery as when I've mentioned self checking before it's not gone down well.I get the feeling that they consider the machine to be a gadget and certainly not as accurate as there tests (it is , I only ever have a variance of 0.1 ) My question is - is self medicating safe as I think all doses of Warfarin that one takes is registered on a national data base ? What else can you do though when it's only checked every 6 weeks ? I have previously had a TIA and stroke and am obsessive about keeping in range.What would you do?

11 Replies

INR is a very vague measurement as we were told at HRC last year. A sample taken to three different labs would produce three different results. If you use a coagucheck machine at least you are working to the same scale each time. but the recommendation at HRC was to aim for 2.5 to 3.5 rather than 2. to 3 and that there was little risk going up to 5 if things went over the top. I have my tests every 84 days as I am quite stable apparently and have been taking the same dose now for many years.but some people seem to have terrible trouble staying in range.

I've never heard of a national data base for warfarin but I see that all our medical records are going to be pooled unless we opt out. Given all government's inability to keep computer records out of the hands of hackers and big business that scares me. let alone the discs that will inevitably get lost in transit.



Hi feelj I used a coaguchek machine to keep in range with my drs support it was really helpful to know that warfarin wasn't going any higher. Good luck ! Teresa


Hi I self test and quite often adjust my dose by up to 1 mg to keep in range.. I did once tell them at the surgery and they were o.k. but wouldn't write my adjusted dose in yellow book as they hadn't recommended it! I make sure I write my own alterations in and sign it in case I'm ever admitted to hospital or anything else unpredictable. I can't see any harm in it if It helps me stay in range.The only snag is that the surgery think I'm really stable because I always make sure I'm in range. X


I have adjusted a couple of times and would do so again if i went much out of range


Thanks to all of you.Glad I'm not alone in making my own decisions .Like Dedeottie I do write my alterations on a separate paper in my yellow book.


G'day Feejbee,

I am usually comfortably in range, but, on my last trip to Australia I twice had to adjust my dose. I chose the day which was a 6mg dose and tweaked it by 1 mg. Job done. Since I've been back in UK I've been in range. I've been on the stuff for 4 years now and have had my Coaguchek device for about 3 and half. I wouldn't attempt this practice until I had a wealth of experience of understanding how my body adapts to warfarin. Matter of interest my practice also is in the 'Dark Ages' and I have (using my Coaguchek device ) proven to my surgery practice that their tests were giving me a wrong doseage - and had a letter of admission/apology from them !!! Also my device results with the Coaguchek device compared to the surgery blood letting are usually + or - 0.1 variation. I'm now on 70 day tests now. What would I do - just carry on and don't tell them BUT do keep your own records. I don't use the yellow book - keep mine on INR software on my computer and every so often download it to hardcopy..


Aussie John


For me a visit to the local blood clinic is no hardship so I tend to go much more frequently than the 'next visit due' dates shown in the yellow book. As a result I rarely go out of range which I know I would if I followed the warfarin clinic's programme. This has only once been questioned by the blood clinic and the warfarin clinic have never commented. So if you really are obsessive, like me, then don't take 6 weeks as cast in stone.

Like you I am proabably going to get a coagucheck machine - I'm just waiting until my next cardiologist visit as I know he wants to talk about Dabigatran - and I see nothing wrong with a bit of self-tweaking of the dosage here and there. At the end of the day all that is important is that your INR never drops below 2 (or better still, 2.5) and not all of us can guarantee that if there are long gaps between blood tests.


Hi Feejbee,

I self monitor and self manager - i.e. I adjust the dose myself. I don't tell the anti-coag clinic to keep things simple. Fortunately I'm very stable so it's just a matter of adjusting 0.5mg one way or another. I don't think it matters that central records at the clinic are not always up to date. If I had to go into hospital and was not compos mentis enough to tell them what's what, my INR would be all over the place anyway due to being fed by a tube etc.

I do take Vit K2 supplement which really helps stabilise my INR.



Hi Mark

Interested in vitamin K 2.Not heard of before .What does it do?



Vitamin K or K2 helps stabilise INR values. The idea is you take a steady dose each day and then any variation due to e.g. eating broccili is relatively minor. Several trials have been done and Vit K/K2 is shown to work well, see

I use Vit K2 rather than Vit K as it also helps prevent artherosclerosis. But I suggest you do your own research before taking this as your doctors might not approve.


Thanks Mark I shall certainly look in to this.I find it quite difficult to keep a stable INR and just a little broccoli sends it haywire so anything that might help is worth a try.



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