Increased heart rate on T3: Hi to everyone. Have... - Thyroid UK

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Increased heart rate on T3


Hi to everyone.

Have been gradually increasing my T3 under the guidance of an endo am now at 45 mcg. Am still not symptom free but do think the T3 has helped some of my aches and pains and my brain fog is lifting. My only issue is that my pulse which when resting is normally 72 beats a minute is up to 90. Not drastic but I can feel the difference . I am also getting a lot of missed beats as well. My heart is not happy and I am not sure what to do about it. I take iron to keep my ferritin levels up so i dont think that is an issue.. I tried 40 mcg and still had the brain fog, so upped to 45 mcg, maybe I should try 42.5 (I'm thinking out loud now)!

Just dont want to go downhill again. The endo had talked about adding in T4 as he was reluctant for me to go up to 45mcg as my blood results were as follows

on 35 mcg t3 TSH 0.61 (0.35-5) T4 2.5 (7-20) T3 4.8 (3.5 - 5.3)

The endo said I should be feeling well on these results but I asked to go up to 45 mcg, but now have an unhappy heart. Been on this dose for just over a month.

I did try NDT (Armour and Erfa) and got the thumping heart at 2 grains, I did not get any symptom relief with either of these meds.

Could my heart eventually get used to it or do i play around with the dose.

I supplement with vid d, iron, b12 - all the usual suspects.

Any ideas would be great.

Thanks L


43 Replies

This link may be helpful.

lizzie1 in reply to shaws

Thanks shaws will have a read

Lizzie, heart rate usually increases within an hour or two after taking a dose of T3 but should drop back to normal an hour or two later. Your FT3 is still low which is why you are still symptomatic. It's worth trying 42.5mcg but I think you may still be slightly undermedicated. If you don't feel improvement consider cutting back to 35/40 mcg T3 and adding in 25mcg T4. 25mcg T4 is equivalent to 10mcg T3.

lizzie1 in reply to Clutter

Thanks clutter for the reply. Unfortunately my pulse stays high all day. The Endo said my t3 level was more than adequate. Shows what they know! Really hope I can find a solution as its the first time in years that my head has started to clear, cant face going downhill again. Am seeing the Endo next week and will see if he will consider dropping the t3 to 40 and adding in some t4. Thanks again

Clutter in reply to lizzie1

Lizzie, I'm so sorry, I misread your results. FT3 is very good, just a gnat's under the 'ideal' 75% of range and you don't appear to be undermedicated. I don't know what I was thinking :(

I still think it may be worth adding in a little T4 to T3. It may give you the additional hormone you need without the peak effect of T3 raising your heart rate. I found adding T3 to T4 calmed the adverse effects I experienced on T4 only and wonder whether the reverse may work for you.

lizzie1 in reply to Clutter

No worries clutter, we all have brain fog moments! Am definitely thinking of adding t4 to the regime. Unfortunately I cant tolerate more than 37 mcg as I get appalling headaches. I dont want to give up on the t3 as it certainly has helped.

Clutter in reply to lizzie1

Lizzie, I think it may have been wine fog. Had a good lunch and I'm not used to drinking these days.

Taking T3+T4 in combination may mean you can tolerate doses you couldn't on T4 or T3 only. I hope it helps.

lizzie1 in reply to Clutter

Thanks clutter, its given me food for thought.

Clutter in reply to lizzie1

Lizzie, Make one change at a time, ie don't introduce T4 while you are changing T3 dose and timing or you won't know what is helping/hindering. Try 40mcg T3 for 2/3 weeks split into 3 as usual. If that doesn't improve pulse rate then try 40mcg x 2 split doses for a couple of weeks.

lizzie1 in reply to Clutter

Some good ideas there, thank you.

If you are showing cardiac signs I would reduce the T3 (and not add in any T4) even if you get some symptoms. It may be that you have to compromise. On the other hand how fit are you? If you have been hypo for many years and too tired to exercise then moving to T3 over a period of a few months could be too soon. If this is so I'd reduce the T3 and take regular exercise such as brisk walking for many months and then review the situation. It may be that you will no longer need an increase in T3 or that your pulse reduces as you become fitter and you are then able to up your T3 a little. The big question is whether your rapid pulse is due to excess thyroid hormone, if in doubt you have to take a conservative approach. Are there other signs of thyrotoxicosis such as a fine hand tremour?

I'm in favour of T3 but you do need to take note of all signs of under and over treatment. Atrial fibrillation can occur if overmedicated, on the other hand undertreatment also has cardiac and other health problems.

lizzie1 in reply to jimh111

Hi jimh111 thanks for the reply. Have always done lots of sports and currently walk every day. Even when i was running and swimming my pulse was always in the 70's. I cant go back to feeling as dreadful as I did so will have to play around with the dose.

jimh111 in reply to lizzie1

If you reduce your T3 a little and your pulse comes down then the rapid pulse is due to the T3, so you may have to adjust your dose a little. Either way taking magnesium as suggested by greygoose is a good idea. I prefer magnesium citrate but chelated magnesium is OK also. (Magnesium oxide is useless). Magnesium is good for the heart and bones, deficiency is widespread.

How is your magnesium level? If you are deficient in magnesium - which most people are - it will have an effect on your heart. Try taking a little, with some zinc, and see if it improves things. It might save you from having to lower your T3 which, understandably, you don't want to do.

And your endo is totally wrong (as usually!). The correct level of fT3 is the one which makes you feel well. Forget 'adequate'! We want 'optimal'!!!

Hugs, Grey

lizzie1 in reply to greygoose

Hi grey, dont think it will be magnesium as my pulse was ok at 35mcg (although I felt dreadful) and the problem has only occurred when I raised the dose and felt better. Its very confusing re what ft3 should be. I am sure I have read that sometimes on t3 only you usually have to be at the top of the range of even slightly over in order to feel well.

greygoose in reply to lizzie1

FT3 shouldn't 'be' anything. The correct dose is the one that makes you feel well. The blood tests are totally useless when you are taking T3 only because they were designed for people taking T4 only. So, it often happens that the FT3 is over-range and the TSH suppressed and the FT4 low. If you are still feeling bad at your present dose then the odds are it's the wrong dose for you.

How fast did you increase your doses? It is possible, that if you went up too fast, you missed your sweet-spot and are now on too high a dose.

We're all different, there's no one-size-fits-all. I too am on T3 only. I take 75 mcg daily and feel really comfortable on that dose. Many others would find it too high. It dépends on so many things, such as how long you were hypo before starting treatment, etc.

It's all trial and error, I'm afraid. You have to find out what's best for you. Nobody can tell you that - certainly not an endo! But I would still get that magnesium tested, if I were you, if you can. It's almost certain to be low.

lizzie1 in reply to greygoose

It certainly is trial and error.Have you had any issues with increased heart rate while you were getting to your preferred dose?

greygoose in reply to lizzie1

Not that I've felt, no. but when I was in hospital last year, they said I had an arrythmia. I said, but I don't have any symptoms! They said, well, you wouldn't have, would you!!! Which I found rather suspect! But I was taking 225 mcg at the time. So it is possible that there was a problem. lol

But I've read that it's perfectly normal to have the odd missed beat, the heart shouldn't be expected to beat at the same rythme day in day out. Variations should be expected. Have a look at this video and see what you think :

HI It will be the T3 what is your FT3?It must not go over range.


lizzie1 in reply to Jackie

Hi Jackie , my ft3 was 4.8 when taking 35 mcg. The range goes up to 5.3 . Am currently taking 45 mcg.

HI It should be oK but i would try reducing just by 5mcg.I was overdosed by a doc on T3 and had hypo symptoms still.There really is a close connection with the heart as I know my heart is very bad and I have to watch my FT3 carefully, although I do take it.

best wishes,


lizzie1 in reply to Jackie

Thanks jackie, am dropping the dose to 40 today.

Do you take the T3 in one dose or split it up through the day?

T3 is short acting so it enters the system quickly -I used to take T3 and found spitting the dose up into two or three really helped to smooth out the peaks of heart racing. You might also find Paul Robinson's book called 'Living with T3' really helpful; he also has a website and facebook support group -Thyroid UK have a loan library so you can borrow books you don't want to buy.

lizzie1 in reply to waveylines

Hi waveylines thanks for the reply. I split my dose 3 times a day to try and even things out. I never knew Thyroid Uk have a loan library, think I will take a look.

What's your ferritin?

lizzie1 in reply to Neeta-K

My ferritin was 35 but that was a couple of years ago. Have supplemented since so assume it must be higher.

Neeta-K in reply to lizzie1

I would have a blood test to check if your ferritin has gone up

Hi Lizzie, I see Waveylines is the only one who asked WHEN you take your dose of T3. Have you tried changing the way you take it? You probably don't need an increase at this level.

lizzie1 in reply to Heloise

Hi Heloise I currently take it 3 times a day. Just wondering if I should try twice a day. Maybe three times a day is too much and my heart does not get a chance to settle down before it gets another dose.

Heloise in reply to lizzie1

Maybe that would help, giving more time in between doses.

You might want to try taking a very small dose at bedtime too -I know this sounds weird but believe it or not since I have been doing this I sleep better!! ( I take a natural dessicated thyroid that has T3 in it - my t3 content is 4.5mcg of the night time dose)

They say T3 lasts about 6-8 hours in the system -the bulk being more active in the first 5-6 you might want to consider this in your dose taking. My level of dose isn't evenly spread out through the day. I take far more in the early morning ( about half of my daily dose, then a top up in the early afternoon and finally a tiny dose at bedtime. However everyone is different and the author Paul spreads his out with more doses still ( I think he takes his in 5 lots over the day!) it's a question of experimenting. You won't find endos are very good on advising you on this.....but you might find the T3 support group quite helpful. With a normal functioning thyroid your T3 would gradually be released over the day so this is the thinking behind splitting up your daily dose......however there are people out there who are fine just bunging it in on one dose.....we are all different.

Have you checked your adrenals?

lizzie1 in reply to waveylines

Thanks waveylines, no I haven't checked my adrenals. I could not face the fight with the Docs who only seem to recognise adrenal problems when it is Addisons. The private doc I was seeing also said when you are on the right amount of meds then adrenals should get better.

Am going to take it in 2 lots and see if it helps my heart rate.

I appreciate your help.

No worries -hope it works for you.

Your private doc is probably right about the adrenals correcting once your thyroid is addressed -also the NHS testing of adrenals is so basic that you have to have a seriously dysfunctioning adrenal glands to show up on the standard tests.

I chose to take my main dose in the early hours as this is the time that your adrenals require T3 ( and interestingly enough your body has a surge of T3 for this purpose in normal functioning thyroid glands)....this is an approach developed by Paul Robinson ( and is in his book) called CT3M or Circadian T3 Method -it made a big difference in the uptake of my thyroid hormones from the bloods -however if you do consider this approach in the future (not now -too many changes at once are never a good idea) then do be aware that is a very powerful approach and has to be done with real care to avoid over cooking your adrenals.....just thought Id' mention it though for future reference

Hope the two dose per day approach goes well for you :) x

I had this problem when I stopped taking levo and tried t3 on its own (which resulted in becoming v hypo because every time I tried to raise t3 my heart would pound). When I added levo back in it seemed to settle. Like you I still get the skipped beats and that thing where it feels like one side of the heart is faster than the other until they catch up with each other (sorry, not a great description). I worry about it but without t3 I feel drugged.

I agree that there is no harm in experimenting with taking the t3 at different times and you may even want to tweak it further to see if you benefit from a higher dose in the morning and less in the afternoon and evening (or whatever variation you find helpful).

I've tried taking less than my usual 12.5mcg t3 in the morning but it makes it so much harder for me to get out of bed.

Thanks for your comments. I too used to feel drugged on a morning and its only since I got to 45 mcg t3 that the dragging, drugged feeling has started to lift. Is an awful feeling, so difficult to describe. I just was not functioning. I am determined to tweak the dose to get it right.

I get those extra big thumps of a heart beat and then it tries to get back into its rhythm. It sometimes feels likes it is fluttering. Maybe I should get it looked at but I am so fed up with hospitals and appointments that I just live with it.

Thanks again for your reply.

I am lucky(?) that I needed an echocardiogram to look at a recently diagnosed heart murmur (everything looked normal). It was done not long after I started taking t3 so at least I have a baseline in case anything changes.

I understand what you mean about feeling fed up with it all. It's death by a thousand appointments. :-)

Death by a thousand appointments - like it!!

What will work for stability in each one of us is very individual. I com form a family with very hereditary Graves/Hashimoto's across at least three generations -- and none of us have the same medication regime. I was first diagnosed in the US by a very enlightened doctor -- and took T3 only for to begin with. Once we got to a dosage that made my heart rate increase (too much T3), T4 was gradually introduced. In the UK, I was switched to T4 only at a higher dose-- which was a disaster. Now -- I take a 20mcg T3 (sustained release--form the US) and 90mcg T4 daily. Eventually I stopped splitting my dose of T3 over the day -- and take everything at once upon waking-- and this is optimum--for ME. It's all so individual -- but sounds like you're possibly on too much T3 --and some added T4 might help?

Thanks lynnimp for your comments. I am coming round to the idea that i may have to introduce some t4 into my regime. It seems to be a fine line just getting the right amount of meds. 45mcg is putting my heart rate up, but 42.5 seems to be ok. However if I go down to 42.5 I can feel the symptoms returning, its a bit of a no win situation. I am seeing the endo soon so will ask his opinion. He might suggest taking either 40 or 42.5 of T3 and maybe adding in 25 mcg T4.

I just find it so tiring juggling the meds and all the supplements and still feeling unwell. You put so much effort into getting well and nothing seems to work.

Hi Lizzie I was searching and found this thread I am similar to this, raising t3 still symptomatic but heart rate increased. Did you get to the bottom of it ? Kind regards

Dk123 in reply to Arabella33

Hi Arabella, this is a really old thread but I’ve found it today too!

I’ve started another thread today about something similar which you might want to look at and see if there’s any ideas that may help you.

Arabella33 in reply to Dk123

Thank you I did look at your profile, which one was the thread ?

Dk123 in reply to Arabella33

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