Question about warfarin dosage and your INR's reaction time

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ChuckM

Active member
Joined
Nov 29, 2022
Messages
38
Location
Lafayette, La
I'm currently not an at home tester, rather still on the same regimen that was started post surgery. My doctors never really discussed the potential for at home testing, reporting, insurance covered equipment, etc. So I visit the clinic once a month, insurance covers the cost and have been fairly consistent for several months now. I try to watch my diet, but the funny thing about growing older is that foods you wouldn't touch as a kid become the ones that you seemingly love as an adult and then suddenly it all changes.

However to the point, for you at home testers who either self or in coordination with your doctors adjust your meds after testing, I'm curious as to how fast a change in dosage or diet affects your INR. Say you go out and have broccoli with a meal, its followed by a fruit salad with blueberries, and you didn't have a glass of wine. At what point do you test? How much did that one meal make you swing (or does it even reflect a change with one instance?). Either because of this meal or the fact that you haven't checked in a week, you discover now that you're .5 to 1 point low, you adjust your dosage, say add 2.5mg warfarin, how fast does that dosage change appear to affect your INR? How quickly does it "bounce back" to where you are normally?

As one who tests monthly, I've been in my range without change for months now. Suddenly this week's test, I was nearly 1 point low. I of course don't discover until I go for a monthly check, so I don't know if its one meal, one week of meals or one moth of meals.. she makes one day of change by adding 2.5mg to my normal dosage, and I'm just curious if that one change is enough to bring me back into my usual range. I try to remember its a marathon and not a sprint, that the consistency is what counts, but I'm just curious what ya'll who self test see in terms of change over time.

Chuck
 
Hi Chuck

I'm curious as to how fast a change in dosage or diet affects your INR

it takes about 2 or 3 days (depending on some other things) for the new dose to "wash in" as it were. Keep accurate records and you'll know the answer for yourself, because we all do vary a little.

Say you go out and have broccoli with a meal, its followed by a fruit salad with blueberries, and you didn't have a glass of wine. At what point do you test?
none of the foods you mention will make any observable difference to your INR (I encourage you to do some repeated tests not one offs and document what you do) unless you're eating a kilogram (2.2 pounds) of broccoli. The wine may serve to raise your INR briefly and for about 8 hours.

I always test at the same time (more or less) because its a good thing to have habits. Unless I'm doing an experiment in which case I may even (if it is called for) test 4 times in a day. I recommend you actually do a bit of that to make it clear in your own mind that it behaves for you as I'm saying it behaves for me.

How much did that one meal make you swing (or does it even reflect a change with one instance?).
never once experienced one meal making a difference (the wine yes)

either because of this meal or the fact that you haven't checked in a week, you discover now that you're .5 to 1 point low, you adjust your dosage,

I'm not sure what you're saying here, but to the last part I have a method which builds data and from that data I can determine what I'll do to some degree of precision. Its basically a Decision Support System based on pharmacology and data modelling. Its spreadsheet based and relies on you actually doing regular systematic testing.

As one who tests monthly
that's inadequate. Weekly is the gold standard. You'll miss ups and downs with monthly ... heck you're even asking about how long after a meal and then talking about monthly?

but I'm just curious what ya'll who self test see in terms of change over time.

Well for starters On-X tested weekly (IIRC) in their PROACT trial ... perhaps if you have a wide range tolerance and a high target (say, INR=3.5 as the target and anywhere between 2 and 4 is fine by you) then you could test monthly and get few surprises. But if you want to be >60% Time in Therapeutic Range (TTR) to minimise the effects of being out of range then you'll probably want to test more.

See this blog post to get an idea of how many tests were involved

https://cjeastwd.blogspot.com/2022/05/rapid-dust-off-inr-management.html
TTR is strongly correlated for no stroke and no bleed events for very long durations of time

HTH
 
Hi Chuck

none of the foods you mention will make any observable difference to your INR (I encourage you to do some repeated tests not one offs and document what you do) unless you're eating a kilogram (2.2 pounds) of broccoli. The wine may serve to raise your INR briefly and for about 8 hours.

never once experienced one meal making a difference (the wine yes)

I'm not sure what you're saying here, but to the last part I have a method which builds data and from that data I can determine what I'll do to some degree of precision. Its basically a Decision Support System based on pharmacology and data modelling. Its spreadsheet based and relies on you actually doing regular systematic testing.

that's inadequate. Weekly is the gold standard. You'll miss ups and downs with monthly ... heck you're even asking about how long after a meal and then talking about monthly?
And this is probably the basis of my (mis)understanding and my lack of knowledge. Of course I had no previous experience with any of this prior to surgery, but I've simply followed my Dr's orders to this point. For 2 years prior to finding this site, I'd never even considered that self testing and reporting was an option as it wasn't so much as mentioned by any of my care providers. My current testing was/is only monthly unless there's a sudden change and the clinic nurse will schedule a followup in either a week or two. That's the case this time around, because in my previous routine monthly tests I've been in my desired range for several months, until this month's test. It's what's prompting my questions. The foods mentioned really were examples, but not to be taken literally. For clarification, the restated question should be for those (such as yourself) who test weekly, how fast following your consumption of a meal considered high in vitamin K, do you see a change reflected in your INR?

Following your discovery of a decrease in your INR, you adjust your dosage to compensate and this takes 2 to 3 days to reflect. Is this following one dosage increase or a dosage increase over that 2 to 3 day span?

I asked these questions specifically because at the moment I'm relegated to monthly testing, so I'm concerned about the effect of a single meal and the immediacy of its effect. I basically want to know how fast does one's INR change, in either direction, due to either food consumption or a dosage increase. If a single meal doesn't affect one's INR, then how many do? How much vitamin K containing foods can you eat before it reflects with an INR change?

Well for starters On-X tested weekly (IIRC) in their PROACT trial ... perhaps if you have a wide range tolerance and a high target (say, INR=3.5 as the target and anywhere between 2 and 4 is fine by you) then you could test monthly and get few surprises. But if you want to be >60% Time in Therapeutic Range (TTR) to minimise the effects of being out of range then you'll probably want to test more.

My cardiologist has set my range from 2.5-3.5. I've averaged around 3.0 over the past few months (based on monthly testing), but had a drop this month. I'll be returning for another test next week to see how it recovers.. but these are observations that are furthering my interest in self testing. Since my cardiologist hasn't mentioned any process whereby I can test myself, report my findings and have them adjust my dosage, this would be solely for my personal informational purposes. Insurance wouldn't likely pay for the equipment, which would leave me with buying it myself or finding one used, and the clinic would still direct my dosages.

Thanks for the info!

Chuck
 
Of course I had no previous experience with any of this prior to surgery, but I've simply followed my Dr's orders to this point
I understand and I wasn't assuming you should be born knowing. We are all born knowing nothing, but we come here to learn.

Following Drs instructions is a good idea. I classify this differently to orders, orders are to me when you fail to follow instructions or challenge the instructions. Then if there is a difference of view and the Dr feels strongly then these instructions are then elevated to orders.

Myself in the absence of knowing anything followed instructions until things became annoying. From there I began learning and quickly saw I could do better than the 'instructions' ... frankly the discussions of "the insurance wont cover costs" mean nothing to me because
  • most people spend more on a new phone per year than I've done on my coaguchek which has lasted 12 years
  • most people spend more per day on a coffee than I spend per week on the strips for the coaguchek
  • I like to be able to travel and not be tied down like a thing on a chain to a clinic, and pre-covid spent a lot of time in and out of my home country (Australia) for a variety of reasons
  • I really want good outcomes
  • I feel more involved if I'm calling the shots in an informed way than if I'm sitting back and being told what to do. Better yet I know I've had better outcomes by calling the shots
I was just trying to answer your questions and furnish my reasons; rather than just say "because red cars are better then green".

I'm sorry if all I did was give you a bunch of information which is of little use to you.

Best Wishes
 
I was just trying to answer your questions and furnish my reasons; rather than just say "because red cars are better then green".

I'm sorry if all I did was give you a bunch of information which is of little use to you.
Not the case at all, it's all new to me, so its all useful. My intent isn't to discuss the merits of self testing or not regardless of reason. Based on the fact that you self test frequently you're in a much better position to know the answers to my original questions. So I'm still curious:

Knowing you record your regimen, how soon does consuming foods high in vitamin K decrease your INR and how fast does your dosage adjustment affect your INR and cause it to increase? I think you mentioned the increase following a dosage adjustment occurs over a 2 or 3 day timeframe.

Since my doctor doesn't seem to support self testing, a purchase would be for my own benefit, out of my own pocket. So I'm willing to do so if it helps me track my own INR alongside the clinic's official testing. Knowing I only test monthly, I'd like to know at what point in the past month did my INR drop, what did I eat that caused the swing, and when she discovered that drop in clinic and increased my dosage for one night, how fast does it recover.

Thanks again.

Charles
 
Hi Chuck



it takes about 2 or 3 days (depending on some other things) for the new dose to "wash in" as it were. Keep accurate records and you'll know the answer for yourself, because we all do vary a little.


none of the foods you mention will make any observable difference to your INR (I encourage you to do some repeated tests not one offs and document what you do) unless you're eating a kilogram (2.2 pounds) of broccoli. The wine may serve to raise your INR briefly and for about 8 hours.

I always test at the same time (more or less) because its a good thing to have habits. Unless I'm doing an experiment in which case I may even (if it is called for) test 4 times in a day. I recommend you actually do a bit of that to make it clear in your own mind that it behaves for you as I'm saying it behaves for me.


never once experienced one meal making a difference (the wine yes)



I'm not sure what you're saying here, but to the last part I have a method which builds data and from that data I can determine what I'll do to some degree of precision. Its basically a Decision Support System based on pharmacology and data modelling. Its spreadsheet based and relies on you actually doing regular systematic testing.


that's inadequate. Weekly is the gold standard. You'll miss ups and downs with monthly ... heck you're even asking about how long after a meal and then talking about monthly?



Well for starters On-X tested weekly (IIRC) in their PROACT trial ... perhaps if you have a wide range tolerance and a high target (say, INR=3.5 as the target and anywhere between 2 and 4 is fine by you) then you could test monthly and get few surprises. But if you want to be >60% Time in Therapeutic Range (TTR) to minimise the effects of being out of range then you'll probably want to test more.

See this blog post to get an idea of how many tests were involved

https://cjeastwd.blogspot.com/2022/05/rapid-dust-off-inr-management.html
TTR is strongly correlated for no stroke and no bleed events for very long durations of time

HTH
The only thing about green veggies, like lettuce, it is consistency. If you eat green, leafy veggies everyday, it should not hurt the INR. I do not eat salads regular, so when I do, it might do something. I have to make changes to my diet due to diabetes and salads are going to be more often this year. Mainly in the spring, summer and early fall. A1C is doing better. Lost some weight. Makes the cardio happy.
 
I’ve been taking warfarin and self testing since 2000. At Stanford, I was given all the info on getting my own machine. Mine have all been covered by insurance.
I just wanted to comment on eating and INR. Most times I don’t know why my INR goes out of range. (2.5-3.5) I knew for sure it was the bacteria I got in 2008 and then COVID also caused mine to go up. Just lately, it was 2.3 so I added 1/2 tab for the week. Seven days later it was 2.1! I don’t remember eating or drinking INR changing items. Mostly I don’t stress about it. I do, however, agree that self testing weekly is the only way to go.
When I was having symptoms of bacterial endocarditis but it wasn’t diagnosed yet, I probably saved my life by self testing when I saw blood in my urine at night. My INR was in the 6 range and I spoke to a Dr on call. I was told to hold a dose the next day and test again the following day. I did that but my machine gave me an error code. It turned out my INR was too high to be read. I went to urgent care, was tested for everything (INR was around 9), then sent to ER the next day with brain bleed. Whew! I seems like it never happened!!
 
Hi

Not the case at all,
that's good

Knowing you record your regimen, how soon does consuming foods high in vitamin K decrease your INR and how fast does your dosage
it doesn't

I even did a test with a fellow member where he wanted to pull his INR down for a procedure (to be at 1.4) and he juiced spinach. Let me report the relevant bit:

Coumadin stopped. Usual dose 10mg daily. Last dose 10pm day before.

Day 1. No Coumadin.
11am 2.6 INR
12pm 400g of raw blended spinach
4pm 2.3 INR
4:30pm 150g or raw blended spinach
10pm - INR 2.3 (measured twice) no change.

Spinach is about the highest vitamin K food. I would request that you go weigh out 550g of raw spinach and ask yourself "will you eat that in a typical salad serving?"

Why is it so? Well the reversal guidelines for INR are IV administration of Vitamin K (not oral, where the gut plays a role)

this link (US Food and Drug http://ndb.nal.usda.gov/ndb/foods/s...nutrient3=&subset=0&totCount=4878&measureby=m {note, they've changed their site, so my stored link no longer works I encourage you to google it because they now work on cookies not permalinks}) shows that 100g (that's 3.5Oz which of course means nothing to me) of fresh unprepared Spinach has about 373 micro grams of Vitamin K

1675630760786.png


this link (American Heart Association http://circ.ahajournals.org/content/125/23/2944.full ) suggests that guidelines for reducing INR are something like this:
For most warfarin-treated patients who are not bleeding and whose INR is >4.0, oral vitamin K (in doses between 1 and 2.5 mg) will lower the INR to between 1.8 and 4.0 within 24 hours
and for patients about to have a surgery (to get their INR down low) they write this:
For patients whose INR was 1.4 to 1.9 the day before surgery, 1 mg of oral vitamin K was given. Thirty-nine (90.7%) of the 43 individuals in this cohort had an INR <1.5 the next day, and there was no difficulty reestablishing anticoagulation with warfarin after the procedure
So to see a clinically significant drop in INR you need at least 1mg of Vitamin K

Its a thousand micro grams to a milligram (mg) which means that to get your INR down to between 1.8 and 4 from over 4 you'll need 300g of fresh spinach or 13Oz .... in one sitting. Similarly (to the above) if your INR was quite low already (1.9) then the same amount will only get you down to a bit under 1.5

I think its worth mentioning lettuce - it has about 126 micrograms / 100g of Vit K so you'll need 1Kg (about 2.2 pounds) of Lettuce in a sitting.

...I'd like to know at what point in the past month did my INR drop,
if you only test monthly and you find yourself high (say INR = 5) then you just don't know how long you were there ... days, weeks...


what did I eat that caused the swing, and when she discovered that drop in clinic and increased my dosage for one night, how fast does it recover.
it depends, but beware of the grapefruit juice.
https://www.valvereplacement.org/threads/my-monty-python-moment.42094/

But if you give it a hurry-up kick up the butt with a bolus administration of (say) 10% more than your usual probably within 3 days ... its individual and needs to be tuned to you. You can't ever do that if you don't ever do (say) daily measurements and accompany it with good basic documentation. You will forever be doing what someone who just doesn't know tells you to do (without any actual pharmacological evidence).

Remember, doctors don't have a clue anymore about any drug dose titration, they just follow what the phama company said to do (from their experimentations). Warfarin is not a "one size fits all" drug, administration is best done "taylor made"

1675630373984.png


HTH
 
Hi Chuck. I've been self-testing since soon after my AVR in 2014, as I was keen (a) to lead as normal a life as before and so (b) understand Warfarin management was needed to achieve it. Having your own machine obviously also frees you from having to visit clinics regularly.

I may be lucky in that my INR is generally quite stable, but I still test weekly. For me the biggest effects on INR are taking antibiotics (pushing INR up) and having a cold (pushing it down), and indeed a sizeable drop in INR is often the first sign that I am going down with a cold or whatever.

My diet is completely random. I do not try to be consistent with my vitamin K foods. Testing weekly is enough for me; like you, my range is 2.5 to 3.5, and I aim to keep it at 3.0 or above. If I get a reading down at 2.6 or so I will take an additional 1 or 2 mg of Warfarin as a one-off that day, return to normal dosage and then test again about 3 days later and see how it is going, and review my dose accordingly.

When I go on holiday it's usually to somewhere warm and sunny, and my diet changes a lot. Also, alcohol consumption goes up a lot too: from a glass of wine or beer every few days to several glasses of wine, beer or cocktails per day. It's not enough to get drunk, but a significant change. So then I test every 3 days or so of the holiday, and normally have to take a lower Warfarin dose than usual until back home and my normal diet.

From what I have read here and elsewhere about American health costs, buying your own machine and supplies may well be cheaper than the contribution your insurer requires anyway? In the UK the machine itself is about US$370 new direct from Roche, and if I had to buy my own test strips they would be about US$5 each.

So in summary: a single meal would be a negligible change in INR; it's a sustained change of diet that would be more significant.
 
Hi Chuck. I've been self-testing since soon after my AVR in 2014, as I was keen (a) to lead as normal a life as before and so (b) understand Warfarin management was needed to achieve it. Having your own machine obviously also frees you from having to visit clinics regularly.

I may be lucky in that my INR is generally quite stable, but I still test weekly. For me the biggest effects on INR are taking antibiotics (pushing INR up) and having a cold (pushing it down), and indeed a sizeable drop in INR is often the first sign that I am going down with a cold or whatever.

My diet is completely random. I do not try to be consistent with my vitamin K foods. Testing weekly is enough for me; like you, my range is 2.5 to 3.5, and I aim to keep it at 3.0 or above. If I get a reading down at 2.6 or so I will take an additional 1 or 2 mg of Warfarin as a one-off that day, return to normal dosage and then test again about 3 days later and see how it is going, and review my dose accordingly.

When I go on holiday it's usually to somewhere warm and sunny, and my diet changes a lot. Also, alcohol consumption goes up a lot too: from a glass of wine or beer every few days to several glasses of wine, beer or cocktails per day. It's not enough to get drunk, but a significant change. So then I test every 3 days or so of the holiday, and normally have to take a lower Warfarin dose than usual until back home and my normal diet.

From what I have read here and elsewhere about American health costs, buying your own machine and supplies may well be cheaper than the contribution your insurer requires anyway? In the UK the machine itself is about US$370 new direct from Roche, and if I had to buy my own test strips they would be about US$5 each.

So in summary: a single meal would be a negligible change in INR; it's a sustained change of diet that would be more significant.

Thanks for both replies @pellicle as well. That's really the point I wanted to understand, the drop could have occurred anywhere over the past month, but most likely not because of a single one off meal that contained spinach or broccolli or whatever. My clinic nurse pushes the "high K" foods, greens and such (no worry, even though I'm in Louisiana, Collard, Mustard and Turnip greens make me want to puke) are to be avoided at all costs. That if I have any consumption of greens that they are part of a routine so that when combined with my dosage, reflects a steady INR. LIke you, I'm really all over the place on eating. I love spinach, ate some this past week, but probably not in the previously 3 weeks since last test. So of course now I'm lead to believe that it was this one off consumption of spinach that most likely caused it, when apparently its not!

Alcohol consumption is another same exact situation as you. Although I've slowed my drinking as I've aged (did a great job of it in college), it wouldn't be far to say that its usually a good bender for the week or two of vacations. 2 years ago a few months following my surgery when I was brand new to warfarin, I had that week long bender at the beach. By the last evening, I began passing blood. Something I've NEVER done prior so I immediately tied it to the beer drinking all week. Last year we said that if I were to drink heavily for the day, then I'd have a nice big bag of frozen spinach for dinner, you know to "even things out".

So this is the type of info I'm looking for. One's INR shouldn't be negatively affected by a one off dinner, but a week of it maybe so. Alcohol does seemingly affect it as an increase almost immediately though, correct?

I need to look more into buying one. Where would one go in the US to buy one? Casual Google of the Coaguchek said it can only be drop shipped to a medical facility or education facility. I'm pretty sure I'm not wanting to buy one off of Ebay, correct?

Thanks!

Chuck
 
I eat whatever I want and test every 2-3 weeks and manage my dosage.. I'm very cosistent running ~2.5 with a target of 2-2.5. When I used to have the clinic adjust my dose, they said to wait ~5 days for the change to take effect and my systemn reach a new equilibrium before testimg again.
 
I've been going to the Coumadin clinic for 2 years since my surgery. Also, I bought a meter off ebay and test weekly, at the same time/day. I want to know where my INR is at anytime.

I normally go to the clinic every 4 to 6 weeks. (8 weeks this past summer for a huge camping trip) They know I have a meter. I usually agree with their dosing change, if any, but will also let them know when I don’t and why I don’t. Then we normally talk it out. I've shared my INR chart with the clinic too. If when I home test and it's at a level I don’t like and I think I know why, I’ll adjust my one dose without letting the doctor know. Like @LondonAndy holidays - with longer and more difficult hiking and the extra wine, I'll see a difference in my INR.

I have a range for my INR and so I don’t worry too much about what I eat and how much it affects the INR daily. Usually it stays within range weekly. But it’s a great comfort to be able to do the home testing when I am curious about my level. That’s where your question about “how fast do you see changes in your INR”, home testing will help you understand how your eating affects your INR. That will give you less worry about the daily affects.

I do have the option of going through my GP for home monitoring but I like having the doctor/pharmacist over seeing my care. If I have any concerns or urgent questions, I can talk to a doctor that day from the clinic. My GP would be harder to reach, and I’d probably be working with the PA or nurse. (I don’t like his PA much) BUT I like being in control of my care, that’s where my ebay meter gives that ability. Like @Gail in Ca I think, my home testing have saved me twice from having major problems.
 
need to look more into buying one. Where would one go in the US to buy one?
Don't dismiss eBay
EG
https://www.ebay.com/itm/115644917754
a while back there was some absolute bargains. Also its perhaps an old warning now, but do not pick up the S model ... no strips are available and its been superseded by the XS for over 10 years.

PS: no its not an old warning. Wow ... there are still scoundrels selling them
 
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Also re eBay etc: if buying test strips ensure they (1) have a few months of life before they expire as the machine will then reject them, and (2) that they come with a "code chip". Each batch of strips needs the right code to give the correct readings.

A pot of 24 strips will last almost six months, if testing weekly.
 
Chuck - someone on this site sent me a unit - I still owe them shipping charges! - but I can sure pass it along to you. I never fired it up - insurance supplied me one and I have been testing weekly ever since. Thought I may have skewed my results with a lot of skiing over the past week including in frigid cold at Killington - but the test today was 3.1, Within my 2-3.5 range.
 
My experience with self-testing and experimentation, although not nearly as extensive as Pellicle's, has clearly shown that my food intake, in particular foods containing Vitamin K, have a rather quick effect on my INR, definitely within 12 hours. The effect of Warfarin intake, on the other hand, takes at least 48 hours to show up in my INR. Consequently, if my INR is too high I can quickly lower it by consuming food with high levels of Vitamin K. But if my INR is too low it will take a few days to get it back up with an increased Warfarin dose. I realize that this may not be the case with everyone but it is certainly the case with me. It is an established fact that we do not all metabolize this stuff at the same rate and it points to the need, and educational value, of self testing so that you will "know yourself". (To steal a line from the aforementioned Pellicle).
 
I can’t imagine trusting my life to a clinic or testing service here in the USA. Let me quickly give you an example. One of the premier services for managing INR is a company called Acelis. They market that they keep their patients within therapeutic range 70% of the time. In what world is it ok to be in range 70% of the time with a mechanical valve?! None. There is no world where this is acceptable.

https://www.acelis.com/en/healthcare-professionals/inr-patient-care.html
I test at least once a week … but more often I am testing twice a week because $12 a week (the cost of 2 test strips) to catch an issue before it happens is well worth it to me.
 
I’ve used Acelis for years with no problems. Basically, they provide supplies and notify the Coumadin clinic pharmacist of my results which I enter into an app on my phone. My cardiologist wants me to test weekly and that’s fine. I had to go this route after my 3rd surgery due to bacterial endocarditis. Before that I tested and dosed myself for years.
All my supplies are covered by insurance so no more searching on eBay for me.
 
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