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As well as cold intolerance, where you can be extremely sensitive to cold temperatures, heat intolerance can be a symptom of thyroid disease, too. This symptom can also be made worse by rising temperatures outside.
If you feel easily hot, especially compared to others around you, have hot flushes and don’t do particularly well in warm weather, this may suggest that you experience heat intolerance. This can be linked to hypothyroidism for a few reasons.
Over Medication for Hypothyroidism
I would firstly check that you’re not over medicated on your thyroid medication, as being so can lead to hyperthyroidism and thus cause symptoms such as feeling hot, flushed and anxious (see here for hyperthyroidism heat intolerance).
You need a full thyroid panel (note: full, not just one or two tests) doing to include TSH, Free T3 and Free T4, and thyroid antibodies TPOab and TGab wherever possible. A suppressed TSH can be normal on thyroid meds containing T3, but your Free T3 and Free T4 should be within range, for hyperthyroidism to not be present. TSH alone is not accurate to go by. Please see optimal levels here. 
Another thing to keep in mind is that if you have autoimmune hypothyroidism, which around 90% of us with hypothyroidism do, then this can cause us to swing between hypo and hyper symptoms, causing intolerance to the heat and cold, so should you be having a Hashimoto’s flare from this, it can cause increased intolerance to temperatures.
To check for Hashimoto’s and to monitor how you are doing e.g. if it’s calming down, you need those two antibodies tests TPOab and TGab doing. You can read how to better control it here. Find out how to order your own testing here.
Also a part of the same system (the endocrine system) are your sex hormones, which often work in tandem with your thyroid hormones.
When one goes wonky, so can others.
Sex hormone imbalances coming hand in hand with thyroid problems seem to be increasingly common, so testing your progesterone and oestrogen levels is often very helpful. If a doctor won’t do this for you, you can arrange it yourself. If you’re of a particular age, considering the menopause or perimenopause would also be a good idea for your heat intolerance symptoms.
The adrenal glands are also part of the endocrine system and many thyroid patients find that they develop adrenal dysfunction on top of thyroid disease.
Adrenal fatigue (note: it is more accurately referred to as hypothalamic-pituitary axis dysfunction) seems pretty common among thyroid patients and testing for it with a 24 hour, four point saliva test will show if you do indeed have it.
When I had high cortisol adrenal fatigue, it was causing me to have hot flushes where I became unbearably hot and sweat buckets. Even in December!
What you need to keep in mind about your thyroid, is that it’s basically your body’s thermostat, regulating body temperature. But when you have a thyroid problem/thyroid heat intolerance, it won’t adjust or adapt to colder or warmer external temperatures like a regular person’s, which means you can struggle in the heat. Or the cold.
As well as taking into consideration the above info and exploring them, some of these tips may also help you to cope with feeling overwhelmingly hot.
- Take a cool shower before bed to cool down and remove sweat and stickiness.
- Replace a heavy duvet with a light sheet.
- Spray your bed sheets in cold water so that as you lay on them, they’ll slowly dry but help keep you cool in the process.
- Drink cold drinks, preferably water, with ice.
- You can also suck on ice cubes to help you cool down and hydrate at the same time.
- enjoy ice lollies and ice cream!
- Applying bags of ice cubes, ice packs or frozen peas to your wrists, back of neck and feet can also help cool you down.
- Consider investing in a fan or air conditioning at home, especially in the warmer rooms of the house and your bedroom so that your sleep is affected as little as possible. You can also try placing bottles of frozen water behind or in front of fans for a cooler breeze.
- Keep curtains and blinds closed during the day to keep heat out.
- Use cotton bed linen and clothing as it is breathable and allows ventilation.
- You can also stick your bed sheets in the fridge or freezer (in a bag) for 5 minutes or so before bed, to cool them down, too.
- Look at investing in a Chillow.
- Wear lighter colours such as white that reflect sunlight and avoid black and dark colours which can ‘absorb’ some heat and make you feel warmer.
- Wear loose fitting clothes for ventilation.
- Snack on frozen fruit.
- Run your wrists under cool water.
What other tips would you add? Let me know in the comments below.
You can click on the hyperlinks in the above post to learn more and see references to information given.
Margaret KarchesyJuly 27, 2020 at 10:43 pm
Rachel My name is Margaret Karchesy I live in Corvallis Oregon Am 75 years old and have been hypothyroid for 47 years Was on 88 mcg of synthroid for along time and just now came down to 75 mcg I need to know i if some of my symptoms could be tired all the time and occasionally I have bad mood swings and crying jags I don’t tolerate heat at all. I have since switched doctors I had one that retired 2 years ago and when i went in for testing she would tell me not to take my pill before testing and take it after testing She was testing every 3-4 months Went to 2 other doctors that were only willing to test once a year I quit them I know the symptoms when its off I do have another doctor now that tests every 6 t0 8 weeks Thank you for any help you can give me
GraceSeptember 27, 2020 at 5:54 pm
Thyroidectomy and cold most of the day until I exercise and then I end up sick and overheated. So annoying!
Virginia TristanJune 28, 2020 at 7:15 pm
Good article. I’m experiencing some of these issues as well..
PattyMarch 8, 2020 at 4:45 pm
Chapped cracked lips Any suggestions
DeniseMay 27, 2019 at 4:14 pm
I have hypothyroid and take 100mh of levothyroxine every morning. I have a very bad heat intolerance. I live in southern louisiana where it’s very hot and humid. If I am outside in the heat for a little while I will get a sever headache and be come physically sick and begin shaking and sweating for hours and end up at the emergency room. It doesn’t matter what I do it doesn’t stop until I receive help at the emergency room. I can take cold showers, baths, drink plenty, nausea meds. Nothing helps. I just got referred to a endocrinologist after dealing with this for 11 years.
Rachel HillMay 28, 2019 at 12:35 pm
Hi Denise, hope you get some answers soon.
ElFebruary 4, 2023 at 12:09 am
I have had the same issue for 10+ years.
Heat intolerance is RUINING my life. Have you found any answers? Sending wishes.
DonnaAugust 18, 2018 at 9:21 pm
I bought several cooling towels – the ones that look like scarves – I put them in the freezer at night and have them for use during the day. They do help bring body temp down a bit.
Rachel HillAugust 20, 2018 at 9:46 am
Glad to hear they help!
MarkJuly 9, 2018 at 7:41 pm
I’ve struggled with anxiety, depression, fatigue, and finally now fibro and HORRIBLE eczema. Years ago I’d discovered a book by Broda Barnes but was dissuaded off it by my PCP who wanted me to go on SSRI’s. I fired him but suffered debilitating fatigue, etc until this past year.
I started applying iodine tincture to some of the eczema patches now covering my body. It helped so I tried it on my feet as well and all the scaly skin on the bottom of my foot disappeared in ONE treatment!
The fatigue and eczema didn’t quite get under control until I added CBD (to help with healing) Omega-3, and Raw Glandular extract (I’m not sure I can recommend the brand).
The glandular (with adrenal, pituitary, etc) meant the difference between sweating in New England heat and succumbing to it with migraines. BTW to you folks who drive on the wrong side of the road, the heat index has been 110 to 120 F most of this summer.
Last year I would have been confined to a room with AC. Now I can at least function, assuming I keep hydrated. ANY salt you consume to replace that lost from perspiration should be Celtic Sea salt. You’ll need a separate source of iodine which I recommend A-F-T-E-R getting Hashi’s under control. I’m still working on getting mine under control so I pulse dose iodine.
One more thing, I strongly recommend googling Broda Barnes MD, David Brownstein MD and Lynne Farrow (freelance reporter).
Rachel HillJuly 9, 2018 at 7:42 pm
Thank you for sharing Mark!
Nariman Abel (mrs)April 26, 2018 at 8:07 am
I am hypothyroid, taking 100 mcg of thyroxine every morning. I am also diabetic and on medication.
I am really feeling very hot these days due to weather conditions, but ALWAYS feeling hot. I also feel certain mood changes and tired especially in the afternoon. Problems sleeping. I’m a woman of 63yrs retired from work.
Rachel HillApril 30, 2018 at 3:19 pm
Sorry to hear this Nariman. It’d definitely be worth exploring the possible symptoms for the heat issues mentioned in this article. Have you had your thyroid levels checked recently?
ChadJanuary 17, 2018 at 12:30 am
I am a 40 year old male with hot flash issues, high bp which is treated but spikes daily in the afternoon, and have been told all thyroid tests are normal. My total testosterone was just tested in the am and was 184!!! I just recently started TRT. The BP spikes and hot flashes always occur after lunch. Just curious if there could be a correlation with the spikes being in the afternoon with the circadian rhythm of thyroid or testosterone???
Rachel HillFebruary 26, 2018 at 6:14 pm
Hi Chad, I’d recommend joining my group for more direct help – https://www.facebook.com/groups/449586315231741/
Joy RaeJune 27, 2017 at 4:12 pm
Hi Rachel! When I was a kid, on those hot summer days, my mom would wet our hair and braid it before bed. Having our hair wet, and a fan on in our room, would help keep us a little cooler.
Sometimes I would put a few inches of cold water in the bathtub, add lots of ice cubes, and stick my feet in it whenever I was overheated.