AF Association
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how long does it take for warfarin to work ?

i was put on warfarin just over two weeks ago and my IRN levels were 1.0 and they are still the same they have now increased my dose to 5mg but was just wondering how long it takes to get my level up to 2.5 as i am still suffering attacks of AF. they are only lasting a couple of minutes but i find it quite worrying . i eat a healthy diet with lots of veg and they said this is not a problem as long as i don't change my diet.

9 Replies

I was surprised how long it took to get my INR levels up, as it took about a month in the end, just gradually creeping up each week. They have to be careful and gradually increased the dose, having too much is not good for you. My INR is around 2 now and they are happy with that, like you 2.5 is the golden figure to get. The cardiologist told me I would have to be in AF for a 48hrs with no warfarin to have any worry about having a stroke. Try not to worry, I'm sure it will get higher soon, worry is no good if you have AF, but easier said than done! Good luck and let us know how it goes. Wendy.


thanks wendy you have put my mind at rest. as i have had very little information on AF and everything that goes with it. i hope to get more answers when i see my consultant next month. just so glad i found this site and thanks again. julie


sheffieldlass, In some, they hit there numbers really quick but for most it takes a while. Mine took about 6 weeks to get leveled out. and has been pretty much constant since.



HI Shefieldlass

It depends and some of us seem to be very reactive to warfarin, and some not, I'm on two weekly tests now, and Monday just gone I was 3.8 and two weeks previously 1.8 and that's with no change of dosage.

The nurse will drive you over 2 very quickly, and don't worry about what the dosage is, it's not really relevant if you take 5mg or 15 mg, (deliberately exagerating) it is only the INR that counts.

Me I drive the poor anti coag nurse mad, and it's not deliberate I assure you, and I don;t change diet either, I am just difficult (story of my life :))

You'll be in range very soon I assure you

Good luck



thanks for the information everyone it is very much appreciated julie


Pleased to help Julie, we have all been there. Although I don't really like being on warfarin when I get an an AF attack, I am really pleased that I am on it, giving me protection against a stroke. Write down all your questions for next month to take with you to see the cardiologist, but some of the answers may be on this website, so take a look, it really helped me when I was first diagnosed. Take care. Wendy


It is really strange how different clinics seem to approach this problem. When I started they gave me 10mg for two days and then tested every day till I got close and then played around with the dose until I stabilised. That doesn't seem to happen these days and they creep up on it gradually. As has been said the actual dose is not important it is stability which is so keep to a steady diet with no massive swings and you should be OK Me, I'm stable and only have three monthly INR checks and vary within the two to three range at 4.5 mg six days a week and 5mg on one day each week.


Thats opposite, wafarin and coumadin lower your levels. 1.0 is actially a good 0 number, but 2.5 is perfect


Hi, I have been on Warfarin for nearly 5 weeks now and have only gone from 1.0 to 1-6 ! Was up to 1.8 and have now gone backwards ! Finding it really frustrating !


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