Hi Song4she & Liz40, Good question. I am a GP (and Michael’s wife) and have been following the Intermittent Fasting movement with real interest. Thank you, you’ve brought up an important point here. Fasting may interfere with your warfarin to enhance its effect (putting your INR result up) making your blood less likely to clot and so could increase the risk of bleeds. Warfarin works by slowing the production of vitamin K which is needed to help your blood to clot.
This effect of fasting on Warfarin seems to be confirmed anecdotally as well as in study done in 1976 on the impact of fasting on rats who were given warfarin. The researchers found fasting had a significant effect on enhancing the antiprothrombin response to warfarin, ie increasing the anticoagulation effect and as a result the blood is less able to clot. This study also found that fasting didn’t alter the effect of Vitamin K which can be used to reverse the warfarin.
It is worth considering factors such as; How stable is your INR? Are you frequently having to alter your warfarin dose so you are not over or under anticoagulated and so more at risk of bleeds or clots? How vital is it that your INR remains at a certain level (eg for a replacement or mechanical valve)? In such cases it is worth being particularly cautious when doing anything that might alter your INR levels.
It is worth discussing with your doctor prior to fasting when on warfarin as it is may alter your blood clotting. However it is also worth remembering that on the Fast Diet you are only restricting calories on your fast day so it will have considerably less impact, particularly if this is done on non consecutive days and the calories are reasonably spread out during the day.
It may help to eat foods rich in vitamin K on your fast day to counteract the possible effect on increasing your INR (foods such as liver and most of the green leafy vegetables you are probably eating on your fast day anyway!) It would be wise to increase monitoring of your INR if you start Intermittent fasting to see how you respond. Portable home INR testing monitors are now available to help check daily variations. These are considerably more expensive than glucose monitors but many GPs have these for use in the surgery. Your GP may be able to help with more frequent testing for a short period to see how you respond. Sorry this is so long but I hope it’s helpful.

Hi Liz and Clare

Thank you Clare for replying. I am going to go to my doctor and ask her advice as I am also on beta blockers and statins.

I started the Fast Diet a few months ago and lost about 6lbs, but altogether need to loose about a stone and half. My INR was up and down, which was unusual, therefore stopped following it. I feel that I could ask my doctor if she would like to use me to monitor progress and change. I am 58 and was diagnosed with AF 5 years ago. I no longer want to be a size 20 and I am hoping that this way of life will work.

I will post my progress if that is ok.

Thanks once again.

Sheila

I was on warfarin for many years until the newer agents came along. I’m now on rivaroxaban (brand name Xarelto) which isn’t diet sensitive. I have also taken dabigatran (Pradaxa). I would not have been able to fast on dabigatran because it caused so much stomach upset, I had to take it with food.

But as for warfarin, the classic advice about warfarin is to maintain a constant intake of dietary vitamin K. According to a review from Tufts University published in 1997, It’s actually easier to maintain a stable INR if you maintain a higher vitamin K intake every day, than if you keep it lower. A 2010 study from South Korea confirms this. The good news is that it’s easy to incorporate a high vitamin K intake in the Fast Diet, because vitamin K is high in green vegetables. I would suggest getting your INR stable on a high intake of vitamin K prior to starting the diet. Then you can include the high vitamin K foods on your fasting days. The fact that you’re getting a lot of vitamin K every day makes it less likely that your INR will be unstable. Also know that at any given time, your INR is a result (mostly) of proteins that last several days in the bloodstream, so the INR and the clotting capacity of the blood is a sort of rolling average of the action of clotting proteins over the last 5 to 7 days. On the diet, your INR will reflect a sum of the production of clotting factors of several days, which include both fasting and eating days.

By the way, one of the ways to know what foods have vitamin K is that vitamin K in plants is a cofactor of chlorophyll. Vegetables that are green with chlorophyll are also high in vitamin K. Leafy greens, asparagus, and broccoli, for example, are all high in vitamin K. Nuts have some vitamin K too. Not all foods that are green, though, have a lot of vitamin K. Green tomatoes don’t have much vitamin K. Avocados are notoriously unpredictable in vitamin K content. You can eat avocados on warfarin, but don’t rely on it to keep up your intake of vitamin K.

Hi Amber, What terrible luck to have had stroke and I’m so pleased for you that your eyesight has since recovered. As you say it’s about balancing the (probably small) risk of fasting affecting your response to warfarin and the potential significant benefit of losing a few stone in weight. Wise to check with your doctor and perhaps monitor your INR more closely at first. It seems reasonable to try 1000 calories on your fast day in the mean time – perhaps with plenty of green veg as helpfully recommended by pdquick. Good luck with shedding the extra weight and I hope you get the benefit you are looking for. Let us know how you get on

Reading pdquick comments about Vit k, I was told to keep away from them especially asparagus & lettuce, kale, greens etc. hence my vitamin k intake is low. Shall build that up slowly and see what it does to my iNR, if anything. Valuable advice as not given much help.

This is very useful. I take Warfarin and I’ve been fasting for almost a year and it has had no discernible effect on my INR. Until about 4 weeks ago I was having a breakfast, lunch and dinner on my fast days. However I decided to change to skipping lunch as I had reached a plateau of weight loss and I had also noticed that fasting seemed most effective among those of my friends who did that.
On the first visit to the INR clinic after the change my INR had gone up to 4.8 from its usual range of 2-3. I was told to stop for 2 days, to reduce my dose by 1mg and to return in 2 weeks. I went back this morning and found that despite the changes to the dosage my INR was at the same raised level. I can only attribute this to the change in my fasting habits, particularly as I fast the day before I have my INR check.
The nurse and I have been scratching our heads this morning about what was causing this change and now I have the answer. Thank you.

I have recently been told I have Thrombophilia and am heterozygous for factor V Leiden(following a stillbirth due to IUGR and placental thrombosis ). I’m currently not on anticoagulant medication but have an increased risk of DVT. Does anyone know how intermittent fasting could affect my blood clotting process in a positive or negative way?

I am not on Warfarin but I am on Eliquis 5mg twice daily for AF. I also take beta blockers and Digoxin. I would like to gradually lose some weight particularly as I have severe OA both knees. I am female aged 85 and am soon to have the cardioversion procedure. I would appreciate any advice about starting the 5:2 diet. Thank you.

Hi,

I have read your post and I am just about to start 2 weeks of 800 calorie fasting. I take rivoroxaban now after having taken warfarin for 5 years following a large unprovoked DVT. I feel from your post that there are no health risks with the reduced diet and rivoroxaban or should I see my GP before starting. I need to lose about 3 stones in weight so am keen to get going having read the fast diet book.