Can't stand the cold? No, your blood doesn't 'thin' when you move to a different climate

Even though moving from a cold to warm climate, or vice-versa, can change your blood pressure, it does not thin your blood. What you're feeling is perception.

WINSTON-SALEM, N.C. — Are you hot-natured or cold-blooded?

It's quite interesting how two people can be in the same environment -- for the same period of time -- and one will be taking off layers, while the other is reaching for a sweater and space heater.


Producer Tom Santaniello said, "It's that time of year again. It's cold -- like, really cold -- but it's not as cold as it is where I'm from, which is New Jersey. I thought that the warmer winters would feel a little better, but they don't. My dad says when I moved from somewhere cold to somewhere warm, my blood thinned."

Santaniello asked the VERIFY team if the claim is true.



Our sources agree the claim is false. Blood does not thin moving from a warmer climate to a colder climate, or vice-versa. There is a reason a person might feel that way, but it is not medical.


P.J. Miller, MD, assistant professor of hematology and oncology, concluded, "This is actually what we'd refer to as an old wives' tale, meaning there is no significant medical evidence behind this question that that actually happens."

However, he noted many people do experience less tolerance for the cold when moving climates. 

"A lot of that has to do with the perception and getting used to a warmer climate or getting used to a colder climate," he said.

So, while blood thickness does not change with the climate, blood pressure can.

The Mayo Clinic explained blood pressure is generally higher in the winter and lower in the summer. Low temperatures cause blood vessels to narrow, so blood needs more pressure to move through the thinner veins and arteries. That does not mean the blood is changing, even though it is reasonable to think so.

"I, myself, grew up in New England and then actually lived in the mid-Atlantic for a while before living in a tropical climate for a few years, and now I live in NC," Miller said.

He recalled, "I do remember the first time I traveled from a tropical climate back to a New England winter, and remembering how particularly cold that winter was, but again, that was all perception."

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