AF Association
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Self dosers, how do you do it?

In another thread someone said they would like to know how others manage their self dosing. I too am curious. Possible relevant questions are:

1. What is your target range?

2. What do you do if your INR is too low?

3. What do you do if your INR is too high?

4. What images do you use, eg, paintbrush, or water reservoir?

5. What initial information/experience did you have?

24 Replies

In UK I am not aware of anybody allowed to self dose. Self test yes as NICE guidelines support this but dose is normally a matter of testing, calling your clinic with INR and being given the next dose. Totally independent dosing would not be supported in terms of supply of strips, prescription of warfarin etc, I fear. I do know that some people do alter dose themselves from experience  ( I do even though I have my tests done at medical centre) but total independence may be a step too far for most GP practices.


Times may be changing in our favour. Google "warfarin self management uk" and pick to see only the last year. Here are some of my initial finds:

"Self-monitoring can involve either self-testing (where the user performs the INR test themselves and then contacts their health professional for advice on any change to the dosage of anticoagulant that may be required) or self-managing (where the user performs the INR test themselves and then adjusts the dosage of their anticoagulant medication by following an agreed care protocol)." [another question: imposed or mutually negotiated!?  Many of the care protocols I have seen are highly dubious, and I can support my opinion].

I also see that an organisation called "Anti Coagulation Europe" is campaigning for more freedom to self manage. Apparently, in 2014 only 28% of all CCGs allow self management.

If we patients fit best when we follow NICE guidelines, then there is hope.

So, I would be interested to hear from other self-dosers.

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I left this comment on the previous discussion on this:

"I self-manage and have no problems with the doctors. I have warfarin 5mg, 3mg, 1mg and 0.5mg on repeat prescription, so I just reorder as my stocks at a particular dose get a bit low (I like 2 months worth in reserve). I take 8.5mg p.d., sometimes changing to 8mg if a bit high (INR>2.7) or 9mg if a bit low (INR < 2.3).

The Chichester anti-coag clinic think I'm on 8mg but I don't want to rock the boat.

Self-testing has been shown to provide better results than GPs or clinics, and self management is even better than self-testing. So why would a doctor not agree to the best course of treatment, particularly when it reduces costs?"

I think self management is easy when you get to know your own body. I eat and drink what including green veg most nights (but not in huge quantities). I'm in INR range 2-3 about 99% of the time.

I'm probably being really thick bit I don't understand your Q4?


Q4. What image do you use. 

This is important. The first introduction to warfarin management for me, in 1993, was two comments. 1, the half life of the medicine, therefore it takes two days to see a dose change. 2, it is like a paint brush, which has a 'charge' on it, then you top up to the extent you take off.

Easier, is the reservoir image. Your INR represents the level in the reservoir, which leaks. Provided your warfaring = leaks, no problem. Sometimes the level goes down. In which case you need to boost it up, then go back to normal dosing.

If you view it, as In = Out, then you miss out the intermediate step, and you end up in simplistic dosing schemes.

I am interested especially in Q2 and Q3. They are different, because low is more dangerous than high.


OK, thanks. I had just posted a reply to this but that seems to have been lost in the ether.

I use the reservoir image. For instance, as I posted a few months ago, I tested deliberately missing a dose for 24 hours. I tested myself every few hours with some strips I had spare. My INR dropped to about 2.1. Then I simply took the missed dose on top of the standard dose. This brought back my INR to 2.5 very quickly. If I had not done this, my INR would have crept back very slowly over many days. 

Using the reservoir idea, this is what you would expect. If you start at a height of 2.5m in your reservoir and lose 1m gallons per day and get 1m gallons in rainfall then the level remains stable. However if it doesn't rain for a day, and your water level drops to 2.1m, you need 2m gallons the next day to bring it back up to 2.5m.

It's one of the things I like about warfarin. If you miss a dose you're still covered. If you were on an NOAC then your reservoir would be empty for 24 hours and you would be at risk of stroke. However, of course, you then only take one tablet of the NOAC to bring yourself back to fully coagulated in a matter of hours.


Hi, this is my first ever reply to a comment on this forum but I do visit here a lot, when I was first diagnosed I spent about two hours a night finding information on here.

Anyway, I self test and self dose my INR and warfarin levels. I am constantly travelling so this is my only option. As far as I know, I am the only person in my local health centre that does this. It does cause problems with the INR nurses as they have to record the info and sometimes get a big angry when I forget to phone in. 

I use an iPhone app called OATBook to record my INR and self tests. I test with a Coaguchek XS and get the strips on prescription. Sometimes I have to buy the strips from the manufacturer if I can't get home to pick more up (pharmacy wont post prescriptions abroad). Most of the time I take 7mg or 8mg on alternate days. If I forget a dose I spread it over the next couple of days to catch up. If I am in one place I can usually keep my INR very close to 2.5 but if I travel somewhere else, INR often gets lower or higher and then I just adjust until I get it right. In my case, it takes four days for the changes to take effect. Not sure if this helps....If I am in doubt I try to keep my INR on the higher side.


I adjust my dose within 0.5mg either way and keep a close watch . I let the clinic know what I have done. I've been on warfarin over 12 years so am quite familiar with my readings .

If my INR drops radically , like it did recently   , then I email clinic and get instructions within hours.


OK. Time to reveal my hand, but I really would like to hear more opinions.

I accept a wider range than is usually advocated. I have plenty of evidence that there are natural swings over over 2 INR.  Low is more dangerous than High, therefore is more likely to result in action. Therefore, the entry point for Low, is point 2 in the algorithm below. 

I think of the skewed curve as having bands. My median is 3.0. My goal is 2.5 to 4.5 with a preference for over 3.0. Notice, due to imperfect equipment doing the tests, this could translate as 2.0 to 4.0, or 3.0 to 5.0, all of which is pretty safe.

My ‘monitor more often' bands are 2.0 to 2.5, and 4.5 to 6.0. The lower band is smaller, and more serious partly because there is a real cutoff point of 2.0 below which there is no real clotting protection. It is risky here too because imperfect measurements might mean a result of 2.0 is closer in reality to 1.5 which is getting really dangerous. 

My algorithm is this when a result is out of range:

1. Check 1 week later.

2. If still out of range, Step for 3 days

3. If still out of range, consider, stepping for 6 days.    then resume normal dosing for 1 week.

4. If stepping fails, then reduce dosage by 5-10%

Stepping is when you have a dose change for a few days, then resume normal dose. 

If there is bruising or other signs of trouble, well, that is another thread.

This is pretty close to the advice given by Kim and Kaatz. p://

Of course, other factors sometimes over-ride this, but you get the picture. For instance, when coming off amiodarone I was predicting the INR would decrease therefore acted faster to correct the INR when it changed. 


That's interesting. You are more tolerant of higher INRs than I would be. I take my guidance from this graph which shows your risk of a clot or a brain bleed at various INRs:

based on this the lowest risk is in the 1.8 to 3.5 range so I use a 2-3 range. I find a 0.5mg adjustment is fine for me if I get towards the lower or upper ends. I also supplement with Vit K2 every day, which stabilises my INR.


Thanks. Very helpful.  I am ready to revise my opinion in the light of evidence. But, the target range of the excellent advice you follow is 2 to 2.5 which is 

1. Too tight

2. It is only 0.5INR which is the error margin for the measuring tools

3. It is unrealistic, given the background natural swings of INR, which are often >2INR

3. It applies only to people with AF. I am on Warfarin for metallic mitral valve, which also predisposes me to AF, but at least meant when AF started, I was well protected and well used to Warfarin. 

4. The INR curve is skewed. The margin for error on Low INR is non existent, whereas there is quite a bit at the other end. There is almost no protection for INR<2. The compensating factor here is that largish warfarin doses have less effect at low INRs than at high INRs. It is much easier to stay in a range of 2 to 3, than in 3 to 4.

I have been taking my guidance from the bjh "guidelines on oral anticoagulation with warfarin - fourth edition" 2011 + my favourite Kim et al Effect of a simple two step warfarin dosing algorithm. I must check to see if there are updates.

So, yes, I am more tolerant of higher INRs than of lower INRs, partly because of how I view the biology and maths, and partly because, apart from brain hemorrhage, the greatest risk is the clotting. And, the brain problem is not an increased bleeding risk, it is an increased risk once bleeding starts-- a crucial distinction. 


Thanks ILowe. However the range I follow is 2.0 to 3.0, not 2.0 to 2.5. I find I can stay in the 2.0 to 3.0 range quite easily. I agree if I was following a 2.0 to 2.5 range then that would be too tight. 

Some people follow a 2.5 to 3.5 range for the reasons you set out, but I prefer to keep warfarin to a minimum. With the lifestyle I follow, I am at a higher risk than average of bashing my head.


Fair enough. Glad you can stay in a narrow range easily. 


Gosh - I read this post and my brain really hurts......

I'm on apixaban - thankfully.   So simple.

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Yes - it brings back to mind the whole nightmare that Warfarin used to be.

What always bothered me (among many other things) was that one was tempted to self manage because the system did not take trend into account. You drop out of range, your dose is increased and every time you go back, your INR is higher (but still in range) and the longer you go before your next test. By the time you get to 2.9, you are expected to swan off happily for 56 days on the same dose. I found it hard to do as I was told at that point and retain my sanity. Do you obey orders or do you descend into deception, adjust your dose and say nothing? Do you own up to your sin?  I just found the whole Warfarin thing challenging and disturbing (old timers may have noticed) and if I had to pay for Rivaroxaban, I would willingly give up many pleasures in order to do so. I find it life changingly wonderful.


But warfarin is really very simple. It takes me 2 mins to check my INR a week, I eat and drink what I want. As I'm nearly always in range, I know I'm better protected on the tried and tested warfarin than on any NOAC where the anticoagulation effect cannot be personally measured.


If you find warfarin simple, it must be great.  I think I only had an INR of 2.5 once in almost two years and it never seemed to be going where I wanted it to be however hard I tried.  It was mostly around 2.0 or heading over 3 both of which I found unsettling.   You can measure it, yes - but where does it go between one test and the next?


It's horses for courses really. Some of us do find warfarin easy and don't get much variability. But for those who can't, I agree, NOACs are the best answer.


Perhaps I would have done better if I had tried taking vitamin K but I was far from being star pupil at the warfarin clinic and quite keen not to rock the boat as it already seemed to be on a choppy sea.


I haven't told anyone that I'm taking Vit K as there would be a sharp intake of breath and I would get a lecture! There are only so many battles you can have and the clinic doesn't seem particularly open to new ideas!


Best to toe the line or appear to do so with mine too. 


"you can measure it.. but where does it go between one test and the next". Exactly. We need the public results of a year where a large group, with all the different variables labelled, test twice a week for a year. The data must exist somewhere. I would love to peruse it. 

Many home testers test weekly, so build up a picture. They can see swings coming and better evaluate if it is a fluke or genuine. 

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The thing with Warfarin is that it can be so fickle.  A change in dose can take a while to take full effect and the applecart is upset if you eat things that drop INR or if you eat or drink things that make it rise.  Or if you have flu or similar.


Self managing because the clinicians are using simplistic algorithms (reasoning frameworks]. Then the problem, the patient sees the situation in a more sophisticated way but dare not be seen to know better. It is ironic when a system designed to help, and staffed by those who have studied medicine etc more than the patient, are in fact LESS competent than the patient. 

To be fair, I have known some good doctors who are able to reason better. In the short time I was under a warfarin clinic, it was quite obvious which doctors knew their stuff. 

Warfarin management need not be a nightmare. But the medical profession needs to develop more sophisticated reasoning modules which take into account things like a wide variation that is natural. 


"Do you obey orders or descend into deception". Good question. It is unethical to do harm to yourself, therefore you must act by what you know to be best. The responsibility for this deception clearly falls upon the clinicians. I fail to see how deception under duress can be morally wrong. After that, it becomes a question of how to wisely handle it, how to manage them in the problem they have created.

In some cultures, a brief 'yes' is not taken to be a lie. It only becomes a lie if you insist on it. The same cultures operate on a 'don't tell me therefore I don't have to act' basis'. Ambiguity is the key. Everyone knows the game. Seems like this culture is coming to UK.


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