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Thyroid UK
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Oral temperature 35 degrees - emergency?

Hi, My oh Chris has been prescribed 50mg levothyroxine by a specialist and has just taken the second day's dose. Yesterday he had a migraine (not unusual for him but he felt there was a connection with the new medication). Today his temperature is down to 35.0. Previously it's been low, 35.4 and up to 35.6 but never this low. He says he feels horrible. I'm just running him a hot bath. Does he need urgent help do you think? I've posted his results previously and will post again if it helps, but I'm struggling with a slipped disc so hard to type right now.


8 Replies

How are his levels of B12 - Folate - Ferritin - VitD - all need to be optimal and not bumping along the bottom of the range - for thyroid hormones to work well.

Migraines are often caused by LOW Iron - iron transports oxygen around the body to all the cells - low iron = low oxygen - and our heads need good oxygen levels - when the brain actually :-)

Often we feel worse when starting thyroid hormones - so hang in there and give it time. How is he taking the meds ? Is he on other meds ?

Cannot see any results on previous posts :-)


Thank you Marz. I've got him on folate and b12 because they are too low, folate especially, but his iron and vitamin D are fine. His reverse t3 was mid range last test and his free t3 right at the bottom. I'm a bit worried he's converting too much to reverse t3. His t4s are off bottom of range.


Do you have the results for the B12 and Folate - how much are you giving him ? Did you start the B12 before starting the Folate/ Folic Acid. How fine were the results for VitD and Ferritin ?

How does he take the T4 ? Any other meds that may be conflicting with the Levo ?

If the TSH - FT4 and FT3 are all towards the bottom of the range - then you may need to read up on Central Hypothyroidism - where the ;problem lies with the Pituitary Gland. Allegedly quite rare - but I have read here that it is more common than people think due to lack of knowledge at GP level.



Some people do experience headache when they first start taking Levothyroxine. It should resolve within a couple of weeks. 35 degrees temp isn't a medical emergency, temp is low because thyroid levels are low. rT3 mid range is fine. FT4 off bottom of range is low so there is little to convert to rT3. Levothyroxine will raise FT4 and when FT4 is higher FT3 should also rise.

The goal of Levothyroxine is to restore the patient to euthyroid status. For most patients that will be when TSH is 0.4 - 1.0 with FT4 in the upper range. FT4 needs to be in the upper range in order that sufficient T3 is converted. Read Treatment Options in thyroiduk.org.uk/tuk/about_...

For maximum absorption Levothyroxine should be taken with water 1 hour before, or 2 hours after, food and drink, 2 hours away from other medication and supplements, and 4 hours away from calcium, iron, vitamin D supplements, magnesium and oestrogen.

It takes 7-10 days for Levothyroxine to be absorbed before it starts working and it will take up to six weeks to feel the full impact of the dose. Symptoms may lag behind good biochemistry by several months.

You should have a follow up thyroid test 6-8 weeks after starting Levothyroxine. Arrange an early morning and fasting (water only) blood draw when TSH is highest, and take Levothyroxine after your blood draw.


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If his rT3 was mid-range, he's not converting to much to T4 to rT3. Especially not if his FT4 is below range. Everyone has some rT3 in their system, it's natural.


Many thanks. You're all very reassuring and informative - much more helpful than the specialist who just said, "You'll feel better." I hope he will, but certainly at the moment he's feeling worse!

The hot bath helped considerably. Got his temperature up to 37 and he's feeling more alive! The house heating is on at 23, and I'm sweating! But if it keeps him warm, that's what matters!

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I'm an adult, and have had temperatures that low when very hypothyroid. At that temp I can hardly move (altho I did have it on a train once, and staggered from the platform to the taxi rank, and then from my fron door into bed, but that would be from lying down to lying down each time). It feels very similar to a fever, confusion, dizziness, sore /numb body, limbs like lead.

I got some relief being in a very hot room. Warm clothes or even electric blanket didn't feel as good as that. I think breathing the hot air and having warmth all over made the difference. Maybe turn off all your other radiators, and turn his room up to maximum, or put lots of portable heaters in the room. Although I would also be wearing a full set of thermal underwear as my pyjamas.


Thank you SilverAvacado. That sounds pretty grim. I'm sorry you've felt so bad :-( I hope you're feeling warmer now.


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