Thyroid UK

Low heartrate

Hello, I am hypothyroid and have B12 deficiency that I have regular jabs for. I have been trying to get fitter and bought a Fitbit. I have started to notice that my resting heartrate is around 47, but when I exercise (run mainly) it ends up around 170-180. Doing little things like up and down stairs can leave me really out of puff but running I can do! I'm not really fit by any standards so can hardly be referred to as an athlete! Should I be concerned about such a low resting heartrate?

7 Replies

Isn't low heart rate related to thyroid issues?

I am not an expert but if you can hit maximum heart rate while exercising then it means everything should be ok. As long as it settles down pretty fast too and does not cause uncomfortable feeling.

I have the same too. downside is that if you keep hitting max heart rate often you might end up wearing a yourself out. You already have thyroid issues and b12 issues. It does not have to mean you should slow down altogether but physical stress consumes a lot of b12 for example.

you could try other sports as well, running is really consuming many ways.

In my case b12 resolved the issue with going on on high heart rate. Now i can keep the steady 130-155 which is best for me without hitting 184 all the time when pushing a bit more. But I am on sublinguals so I stress dose before exercising.


A low resting heart rate indicates your not adequately treated for thyroid or adrenals. For example I use heart rate and body temp readings to reach my optimum dosage with t3 and adrenal cortex.

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Low iron/ferritin can mean that you don't get enough oxygen - low resting heart rate but very high when you do anything strenuous. Low cortisol can cause similar symptoms - low resting heart rate but any stress results in surges of adrenaline which send your heart rate into orbit. Low B12 made me breathless.


Thank you.


I think low heart rate is a problem for underactive thyroid. When I am not medicated properly and have low iron my rate an be as low as 50 and I feel very cold and my temp is only 35.5. Have a look at this chart that shows average heart rates depending on gender and age


Thank you, something's a bit weird! Lol. I'm 37 and overweight in fact on the scale I'm obese. I'm certainly no athlete but my resting heartrate has been as low as 47. I Take 200 micrograms levothyroxine so surely can't be under medicated.

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Its a hard one- When I get my pulse tested at the doctors they say low pulse is good! But then I always challenge them to say I am 5,1 very unfit as until recently I have had no energy to exercise nor to do much. I think my pulse should be minimum 70 for age and less than average fitness.

If I were you I would have a look at the Thyroid UK website at the blood tests that they recommend. If you haven't had tests for Iron/Ferritin, D3 as a minimum I would guess that they are likely to be low. You then need to look at the recommended ranges on Thyroid UK or Stop The Thyroid Madness as we need to have most vitamin/mineral levels at a higher level whereas the lab results/doctors will accept bottom of range as being good enough.

Re the high dose of thyroxine - If your vitamin/minerals levels are not at their best then the thyroxin cannot work properly

Good luck :)


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