AF Association
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Warfarin and grapefruit juice

I met a patient the other day who was on Warfarin for AF and was advised by her Dr. not to have grapefruit juice. I know certain calcium channel blockers, Statins and SSRI’s effect are amplified with grapefruit juice because of an enzyme in your intestine.

Had anyone else been advised to not have grapefruit juice while they’re on Warfarin?

17 Replies

I understood grapefruit in any form was not suitable and the same for cranberries.

1 like

Is that for Warfarin, I’ve heard about grapefruit juice and other meds because of the increased effect in the intestine but I can’t find any research into an effect with warfarin and grapefruit juice.


Yes I was led to believe that warfarin and grapefuit do not go together.

My other half had some pills at one time that didn't go with grapefruit either.


I’d imagine it’s for the same reasons as other medications then. I just thought it was weird because that was the first time i’d heard it in two years


I think cranberries make warfarin unstable and imagine grapefruit does the same. Some things (like ginger, alcohol, chick peas and mangoes) make INR go up; others, notably green things, make it go down.


The research I did sounds like cranberry and grapefruit juice stop an enzyme in your stomach from working and that means the effect of warfarin and some other meds is increased so your INR would increase very rapidly. And yes foods rich in potassium would make your INR decrease because they contain vitamin K which opposed the effect of warfarin


My instructions also pointed out interaction with:

St John's Wort

Garlic pills

Co-enzyme Q10

Ginco biloba

Dong Quai

Bilberry fruit



Saw Palmetto


and any vitamin supplement containing vitamin K

There are also some medications that produce high or low INRs.


Def no grapefruit . I so miss my half grapefruit for breakfast ! Havent had it for 12 years .......grapefruit !



Yes I was told no cranberries and no grapefruit in any form.


I wonder whether if it's the same for NOAC's? I'm on Dabigatran?


It's not the same for the NOACs. As far as I'm aware most things are OK if you are on Dabigatran, but the leaflet that comes with your medication should tell you, or your pharmacist would help.


Thanks for that Rellim296.



I have been on Dabigatran and now back on Warfarin. At no time have I changed my diet. What I enjoyed before I enjoy now including grapefruit and cranberry but in moderation. I was advised to have this mind set by a haematologist consultant 7 years ago and am very pleased with the outcomes.


I'm on warfarin and I eat grapefruit and cranberries in moderation. It has no effect on my INR. I wonder if this is just one of those tales that keep being passed around without anyone researching it properly?

As regards dabigatran, you wouldn't notice whether grapefruit or cranberries interact with it anyway because there isn't a test for dabigatran's anti-coagulation effectiveness that is in use outside the laboratory.


"careAF" makes no mention of Grapefruit nor does it warn against Cranberry as such. Interestingly it lists Cranberry Juice as being high in vitamin K but Cranberries as being low in vitamin K!

NHS advice is:

"Cranberry juice can also increase the effects of warfarin, so you should avoid drinking it regularly if you are taking warfarin.

There is also some limited evidence to suggest that grapefruit juice can interfere with warfarin and cause a slight increase in your international normalisation ratio (INR, which is a measure of how long it takes your blood to clot). So again, it's best not to drink grapefruit juice regularly if you are taking warfarin. However, having the occasional small glass of cranberry or grapefruit juice is unlikely to cause any serious problems."


Two key words there are occassional and small.

I don't have my notes to hand but I am sure that one of the other drugs dispensed for AF also say no grapefruit (? flecanide?).

When I was having the very wide INR fluctuations (fluctuations up to 2.5) the first thing that they asked was I drinking cranberry or grapefruit juice (the answer was no).

In any event people ought to carfully read the ingredients labels on juices because the additives vary considerably, some have quite a lot of sugar added and spome have AF triggers.



yes I was advised not to have Grapefruit or Cranberry's while on Warfarin,



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