INR levels in hot temperatures

I have been on holiday for five days and the average temperature has been 38 degrees during the day and 27 degrees at night. My INR has gone way out of range. I have not increased my usual alcohol amount and have been catering for myself so have been able to eat my usual diet.

Does anyone else experience sharp rises due to temperature changes.

8 Replies

  • Hi, I've not knowingly experienced any change in my INR due to high temperatures but it wouldn't surprise me if it did because the body's metabolism probably changes too.

    I do get a change in INR when away but this is usually down to different diet and more booze! I check it more frequently when away so as to ensure I keep on top of any trend away from my target INR be that up or down. Do you self test/manage?

  • You maybe interested in the following advice!

    Prolonged hot weather can influence your INR

    The package insert of warfarin lists several environmental factors that affect INR's. Weather conditions, especially intense heat, have been known to alter patients INR.1

    Fluctuations in temperature and humidity have a profound effect of patients, particularly the elderly. Heat related stress and uncomfortable humidity (dew point) typical in the summer season elevates patients' INR. While an occasional hot or humid day will not have a profound effect on a given INR, prolonged exposure to high heat and humidity will stress warfarin patients and INR's can easily drift above target INR levels.

    Hot weather over a prolonged period of time has been shown to elevate INR values - even on the most stable patients. The additional effect of humidity and high dew points make it virtually impossible to cool the body and results in the potential for patients to be higher than normal.

    Make every effort not to become over-heated, drink plenty of non-alcohol beverages and keep close to your physician's orders while keeping all summer INR tests. Contact your doctor for further information.

    Bristol-Myers Squibb Company. Medication Guide for Coumadin Tablets and Coumadin for Injection [Package Insert]. Princeton, NJ: Bristol-Myers Squibb Company. 2009. 15-16.

  • I travel a great deal in hot climates and my INR always but always sinks. It just needs checking more frequently and the dose adjusting - I have had no problem getting it done in the Far East and Australia - the yellow book is universal as I in INR is International! I had a piece printed in the INR paper about travelling on warfarin.

  • I visit southern Spain regularly and my INR goes way out of range every time. After looking into this I've been told that it's probably because I get bitten by southern European sand flies that apparently are attracted to Warfarin. When they bite you they inject you with an anticoagulant which results in a raised INR. I have also been told that if you go to a place that is at a high altitude (such as Madrid) this can cause the INR to fall below the range.

  • This is interesting because I get bitten a lot by mosquitoes and I guess as they suck your blood they probably do the same and inject an anticoagulant.

  • While on vacation in the Caribbean my wife was bitten by sand flies. Turns out she actually has an allergy to sand flies, so she had huge urticaria. Doctor there gave prednisone. We actually came home early and when I checked her INR it was 4.4 That reading is awfully high, her highest in the past being 3.2, so we are reducing the warfarin and will check again in 3-4 days. If it's still up we'll go to our internist.

  • There is data to support this theory but my INR always increases while on holiday in Spain and I've not been bitten by a mosquitoes. Tipper did ask whether you self-test/manage your INR?

  • Hi, I'm an engineer not a medic but have been on Warfarin for 14 years and often travel to hot climates. I suspect that the hot climate itself does not affect most peoples INR much but in the heat one does (or should) take in higher levels of fluid. If that includes higher levels of alcohol than usual it will affect your INR. Also in distant places our diets tend to change a lot and local foods may affect our INR to a surprising extent. My advice would be keep travelling, drink plenty but avoid increased alcohol and test your INR more frequently to adjust the warfarin dose as necessary and try not to worry!

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