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Thyroid UK
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Levothyroxine - dry mouth, burning hot and heart palpitations?

Hi Guys,

It's nearly 2am and I'm awake because my symptoms of heart racing, incredibly dry mouth/throat and the feeling of burning up woke me up. My heart has settled somewhat now and I feel less hot but still have this dry mouth. The dry mouth has been for almost 12 hours and I keep drinking water, but nothing helps.

I've only been on Levothyroxine 50 for about 5 days and I didn't take a tablet since yesterday morning, so I'm surprised that I'd be getting side effects so soon, if that's indeed what they are. It's also been very difficult trying to fall asleep generally - so here I am, awake and typing.

I don't want to take Levo anymore. I just don't feel comfortable. I would just please like some advice on how to manage these side effects and when can I expect them to go away.

24 Replies

Hello Britangerine,

Levothyroxine takes about a week to start being beneficial and up to six weeks to saturate every cell in your body. All thyroid hormone replacement can take a while to rebalance and if you have low thyroid hormone, it must be replaced.

Take pill first thing in morning with a glass of water, 1 hour before foods, 2 hours before sups and 4 hours before iron, calcium of Vit D.

Your doctor should retest thyroid hormones six weeks after starting and adjust dose according to results. Symptoms may lag six weeks behind good biochemistry.

Previous posts indicate you are worried Levothyroxine encouraging hair loss. Unmanaged hypothyroidism may encourage hair loss as can low levels of ferritin (advised in previous post).

Ferritin is a storage hormone and your hair follicles actually store ferritin so your body is short, it will steal from the stored supply leaving the follicles short. Insufficient ferritin will not only affect the life cycle and length of your hair but also change its texture.

Low ferritin can cause negative reactions like palpitations, nervousness, and anxiety in someone starting thyroid hormone replacement.

Iron is key for conversion of thyroid hormone T4-T3 and low levels may decrease deiodinase activity resulting in conversion to reverse T3 ( rather than the active hormone). This means you could be hypothyroid (with low ferritin) and yet appear “normal” according to the standard TSH and T4 thyroid labs.

Low ferritin can also be indicative of a later full blown anemia before the red blood cell count begins to decline.

STTM states a high/normal iron & TFS %, with low ferritin (as you have) may be indicative of the MTHFR polymorphism. If you also have high homocysteine levels, it might be worth doing the MTHFR genetic test.

A high serum B12 level (as in previous post) means nothing as is only measuring the amount circulating in the blood. There could be a B12 deficiency caused when the cells are not able to use it properly, so export it back to the blood where it builds, bound to haptocorrin and is then imported by the liver and recycled via the bile to the gut. This is the salvage and recycle pathway for (inactive) B12 and the cells of the body (in general) are not able to use it.

The other transporter of B12 in the blood is transcobalamin, and this is the one that carries B12 from the gut to the cells.

 High serum B12 is not harmful as we just pee it out but it could indicate there is an issue with B12 utilisation and it is wise to perform the active B12 test (link below).

I have big methylation problems (an inability to detoxify and metabolise hormones well). Methylation snps are genetic defects but methylation issues may be due to deficiencies or build ups.

I also have had a insatiable thirst for the last two years. Try adding a little salt to your water as this helps it be absorbed into your cells (as opposed to passing straight through.)


Active B 12 test.(holotranscobalamin)


STTM iron problems


MTHFR info


Methylation issues



Disclaimer: I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.



Dear Flower, thanks so much for your long and interesting reply to Britangerine. I have low ferritin and your description of the consequences fits, on Levo I appear 'normal' according to TSH but am overweight, tired and cannot remember the simplest things.

My weary brain can't read your links now but I'll read them later with much gratitude.

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Flower such a comprehensive answer! I wonder what your thoughts would be about this. I took a homocysteine blood test long ago and it was low. Do you think that would indicate NO mthfr problem or is it possible to be low and still have the polymorphism.



I guess theoretically you could be right as low homocysteine would suggest that things are working too well but I would assume there MUST be other reasons too and so actually have no idea.

I only gave this suggestion to O/P as high homocysteine is (sometimes) associated with a MTHFR polymorphism and this was my own experience.

This is because the MTHFR enzyme converts homocysteine into SAMe (S-Adenosyl methionine) and if doesn't work effectively will raise homocysteine levels.

Also, without enough B Vits the enzymes that turn homocysteine into either glutathione (antioxidant) or SAMe, don’t work efficiently and so will increase blood homocysteine levels.

Low homocysteine isn't good and can promote oxidative stress and imbalances in the detoxifying pathways. This will limit the livers functionability, limiting the body’s capacity to deal with certain kinds of toxins and production of ammonia and hydrogen sulfide, etc. Any liver imbalances can effect the metabolism of glucose and lipids.

Just as high homocysteine can (generally) be reduced by supplementing folic acid, Vit B6 and Vit B12, low can (generally) be raised by reducing these.

However, reducing B Vits may cause deficiencies and homocysteine low readings may be caused by other factors such as a change in sex hormones (menopause ? ), high BP or too much caffeine so it would be wise to consider implications before taking drastic action.

You could test S-adenosylhomocysteine (SAH), Methylmalonic acid (MMA) or sulphate S (urine) but it would be easier just to test MTHFR. Also remember low thyroid hormones can cause high homocysteine levels so maybe over replacement could cause low ? ? ... but who knows ! ! ..


Low Homocysteine


Homocysteine and low thyroid hormones.



Disclaimer: I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.



Thanks, Flower. Well, this is certainly going to take a lot more investigation. Thanks for the links and explanation. I appreciate your efforts as always.



Thyroid hormone metabolised in the liver (primarily) uses glucornidation and sulfation.






Disclaimer: I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.



Goodness, Dr. Wilson's article on Methylation was extremely helpful. It's as widespread as leaky gut it seems. Betaine is an important element it seems which often recommended anyway so perhaps some are enjoying some improvements. Thanks again, Flower.

1 like

Hi Britangerine..you should take your levo as prescribed..very early days for you on it, so has not had a chance to get into your system properly..did your blood work come back as high TSH?...you really do need to carry on with the medication that the doctor gave you...

before coming off Levo you should talk to your doctor and the doctor has started you on low dose levo as you obviously need the meds..further blood tests will check if you are on the correct dose..please persevere until you go back to your doctor

Has the doctor told you to go back for more blood tests after a period of time on Levo?..

I agree with Flower007 as to how you take the levo, although some people do find more benefit by taking it at night...maybe this will work for you..



I have dry mouth and dry lips first thing in the morning ,I LEVOTHYROEINE 25mg 4 x times daily


Why do you take it 4 times a day? One daily dose of 100 would suffice.

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when my doctor put on 25 daily ,bloodtest showed it was enough so I put on 2x 50 but I keep awake during the day , so my doctor took off them and put on 4x25


OK, but do you take it four times a day? Or once a day?


2 piils in morning breakfast and 2 piils in evening with dinner


Well... a) there is absolutely no benefit in taking two seperate dose - T4 (Levo) is a storage hormone, it just stays hanging around until it is needed to be converted into T3, the active hormone. You could take your whole weekly dose once a week and it wouldn't make any difference. You're making life unnecessarily complicated for yourself by taking it twice a day.

b) it should be taken on an empty stomache, one hour before food or any drink except water. By taking it WITH breakfast and dinner, you are reducing your absorption enormously.

There are two things you could try:

a) taking the whole 100 when you get up, with a large glass of water, and waiting one hour for breakfast, tea, coffee, etc.

b) take it just before you go to sleep, at least two hours after your last meal, or more if it was a very greasy meal.

I think you might feel better that way - you may even find you need to reduce your dose. :)

1 like

Thank you all so much for your comments, I truly truly appreciate them. I wasn't prescribed Levo as such, but the doctor reluctantly prescribed me a month's trial because I was convinced my symptoms were thyroid-related.

I went to see a homeopath yesterday and went for a consultation and health screening. My Cortisol and insulin are very high and my DHEA is low - consistent with adrenal issues - which I think is the actual cause of my thyroid related symptoms.

These past few years I have been through a period of intense change - both good and bad and consequently put a lot of stress on my system. I think my andrenals could be the cause of my hypo symptoms.

I will see an endo on the 19th January at Chelsea & Westminster Hospital, I'm hoping that will set me up on a plan where I won't have to treat my body like a science experiment.

Flower, what you said about ferritin really made a lot of sense.

Can anyone advise on the endo dept at Chelsea & Westminster?


So your symptoms could indeed be over medication. I found when I accidentally took several double doses of levo (memory probs) that the symptoms you describe, pounding heart waking me at night, wore off after a week of reducing the dose.


I don't know how your homeopath determined that your cortisol was high. The usual way that the medical profession test cortisol is by doing a single morning blood test. The best way of testing cortisol is by doing a saliva test 4 times in a day. This is an example of a popular test :


People with thyroid problems have found that the saliva test is much more helpful and reliable and informative than a single blood test.

If you really do have abnormal levels of cortisol it can cause symptoms of poor thyroid function all by itself, even if your thyroid itself is healthy.

The wrong levels of cortisol can cause thyroid hormone resistance (the thyroid hormone won't get in to the cells and do its job or the cells don't react to thyroid hormone as they should), and/or you won't be able to convert T4 into T3 adequately. T3 is the active thyroid hormone that actually makes the difference between feeling well and feeling ill. (Too little T3 will make people hypothyroid - underactive - and too much makes them hyperthyroid - overactive.)

If you have abnormal levels of cortisol (too much or too little) then you need to take plenty of B vitamins and vitamin C. Before taking B vitamins though, you should get a blood test of your vitamin B12 level and your folate levels, just in case you are deficient. If you are deficient you may be suffering from pernicious anaemia and would need extra testing. Getting a diagnosis can be extremely difficult once you start supplementing the B vitamins, so get tests first, then supplement later.

There is a lot more to the whole subject of cortisol and thyroid. It's a complicated subject and I'm not an expert.


They tested my vitamin, minerals and hormones via this electronic pulse machine. It flagged high insulin & cortisol and low DHEA. My vitamin & mineral screen showed low potassium, imbalance of sodium and low vitamins A,C and E. Everything else was normal apparently


My triglycerides (fat) was high too - as a result of the high insulin apparently


I've never heard of testing using any kind of electronic pulse machine. I'd prefer to have results in the form of numbers and a reference range. At least then I have a rough idea what is being measured.


Hi I have been on 125 levo for 9 months now put on a lot of weight hair falling out dry mouth Hart dancing but please hang in there 2 months ago my levo is stabled my thyroid now lost 2 1/2 stone and still coming off hair is great the only thing I have is the dry mouth so hang in there



But don't hang in there if you think you are not really hypothyroid at all.


Britangerine, do you have a copy of the blood test results at the time you were given Levo? If you post them here, that would help us help you. At the moment, everyone is just guessing.

Your doctor doesn't have much idea about thyroid, does he - or he's deliberately setting you up to fail. One month is not long enough to prove anything. The levo your taking won't even be fully active in one month. You would need more like three months at the very least.

Do you sleep with your mouth open? Because that would give you a very dry mouth. The heart racing could be because the dose is too low yet. But only seeing your bloood tests would tell us that. :)


Ok if the heart palpitations started after starting levo, your heart has/had to get used to the new energy, 


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