 [ Symptoms ] why do i have a low tolerance to cold weather suddenly  i am in my 20s and have lived in northern us climates my whole life i do not recall the winter months ever being particularly intolerable but over the last 3 years below freezing temps have become agonizing that is not all  i am finding under 70f or cloudy days jacket weather suddenly and i keep my house at 88f triple digit temps do not feel like anything and i can even wear a jacket if necessary for my outfit it is like i have become borderline reptilian what could be causing this shift [ Disease ] sometimes that can happen if you are low on b vitamins like b 12 and niacin so before you see your doctor you might want to consider picking up a good sublingual b complex supplement much more absorbable than pills at the pharmacy or grocery store and try that for a few days to see if it helps they are not expensive and it will not hurt you if that is not the problem