I don't think it is that linear. If warfarin worked so methodically, I think doctors would have a much easier time figuring out the appropriate dosage for each patient.

For me, personally, I take 5.5 each day. Sometimes that results in an INR of 1.9 and sometimes it results in an INR of 3.0. It also depends on everything else going on in my body. Being exhausted or sick, taking other meds, eating a little differently, can all affect how the INR works. With all those factors, I think it'd be pretty hard to see any linear trend in numbers, even if there is one. There's just too many balls in the air with warfarin to be this simple. (But, oh!, don't we wish it was!)

I think if it were that simple we'd not have to test so often. There's stuff on the internet about dosing and targeting a therapeutic range but to me, it's all in theory because to Toss's point, I've been on the same dosage since December I think and my INR has been generally between 2.1 and 2.7, with a couple of sub therapeutics here and there, and one 3.1, so yeah I think all the variables make it hard to calculate things that way. Plus, person to person, I think the dosage increase or decrease even by one or two mgs could have wildly different INR results.

INR is a ratio that involves the ratio of a patient's prothrombin time to a normal prothrombin time, to the power of the manufacturer's International Sensitivity Index (ISI), so right off the bat there does not appear to be much of anything linear about INR. There could be any number of different methods used by medical professionals to get a patient to target INR, but typically they start at some assumed safer level and work their way up. That is, there is an element of guesswork, and maybe your thinking would work just as well as anyone's, though for safety's sake they may choose to try 5mg first before making the leap to 6mg or higher.
Even when some stable dose is found - for those who are fortunate enough to be stable - it is still like steering a vehicle. There may continue to be minor adjustments for lifestyle factors and simple variability over time.
http://en.wikipedia.org/wiki/Prothrombin_time

Most people are maintained on 5 Mg's of Warfarin per day. I take 5 Mg's of warfarin and then take 6 Mg's every other day. That usually keeps my INR above 3.0. My INR has to be kept higher because I have Hughes Syndrome. I don't think there is any linear science to Warfarin and INR levels. There are simply too many factors involved in regulating INR levels.

Jeremy... I'm wondering where you got the information that "most" people are on 5mg a day. I just don't know that that is true and I haven't seen anything on these boards to suggest that it is. Do you have any documentation (research) you can point to? I'd be curious to see it. I know that I take 5.5mg, but I've always felt a little abnormal because my dose was easy to dial in (obviously, since it is close to 5mg) but so many other people's aren't.

I think most people *start* with a dose of 5mg in the hospital and the doctors adjust based on the results with that initial dosage. I mean, they have to start somewhere and I think 5mg is just standard. But I would guess that very, very few people stay with 5mg. I myself have to occasionally throw a 6mg dose in there to stay in range.

I remember reading somewhere that the average dose of Warfarin is 5 Milligrams. I think you can do a Google search and find that info. It could be more for those who have an artificial heart valve, or AFIB. I think the average dose of Warfarin to remain in therapeutic range is 5 Milligrams.

Here is a link to a website that says the average dose of warfarin to remain in therapeutic range is 4.5 Milligrams.

The daily maintenance dose of warfarin differs greatly between individuals, commonly between 0.5 mg/day and 15 mg/day, and often fluctuates over time. The average maintenance dose is about 4.5 mg/day, although this is lower in the elderly.

I read somewhere that Warfarin was most prescribed in the 5 Milligram dose. You have to dig through the page to find the statistics I provided. But the above quote was taken directly from that website. I hope this helps.

Here is the link:

https://www.mja.com.au/journal/2000/172/12/consensus-guidelines-warfarin-therapy

Thanks everyone. Looks like I'm way over the average at 12. All helpful info.

I think you have to consider the age and diet and activity level of a person to know what's "average." For instance, elderly people generally require lower dosage of warfarin than non elderly people. And I suspect the majority if warfarin patients are older.

5mgs is commonly prescribed because there is flexibility in adjusting dosages, ie you can easily double up or cut them in half.

Honestly dosage doesn't even matter; being therapeutic matters.