Low heart rate / bradycardia?: Hi all, I’m 2... - Thyroid UK

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Low heart rate / bradycardia?

lbad profile image

Hi all,

I’m 28 and on 150mg T4 and 30mg T3 / day, split across the day, and have been on same dose for years. My T4 is always mid reference range and T3 high end. Energy levels are generally fine and I feel “normal” apart from occasional periods of feeling awful which I attribute to food sensitivities / autoimmune flare up.

I exercise regularly but am not super fit genetically (never been good at sports etc) so am a bit perplexed as to why my resting heart rate is so low. It can go to 49 over night, hovers around 55 when T3 dose wearing off, otherwise it’s normally around 60bpm. I’m nowhere near an athlete- when I jog I need to take a break every few mins. After a few mins jogging my heart rate is at 160bpm and it goes up to 180 after a 30second sprint which is pretty high, which I’m also confused by if my baseline is so low…

Anything under 60 appears to be either athlete level or problematic “bradycardia”. I do sometimes feel slight palpitations when my heart rate is low. I’ve been to a cardiologist and had all the tests and been told I’m fine, but Should I be worried about this?

5 Replies

Do you have any recent blood results? Similar protocol of T3/T4 and my RHR can be as low as 45; usually when slightly under medicated (consistently below 50). How do you take your T3? I started taking mine in one go and have seen an improvement (RHR usually between 49-55)but suffered with poor sleep. I’m since trying 10/5/5. What’s your BP like? I’ve always had really low diastolic. I’ve had low Hr even when not doing much in the way of exercise; have seen 39 in my sleep previously.

My heart rate was going down to 50, lowest was 47 and it used to make me feel awful when It dropped that low. I was on too little T4. When I was on t3 my endo made me drop my t4 to 75mcg, was on 20 mcg t3 but I got to a point where I was so exhausted I could barely get out of bed. I upped my t4 slowly, I was getting horrible side effects from t3 so I slowly reduced that also. Currently taking 150mcg t4 only. Heart rate is so much better. Going to see how I do on just T4 and see if I can get by.

Thanks guys for your insights! Glad to know it’s quite a common phenomenon. My blood pressure is also on the low side but always has been. I take my T3 split into 3 when I wake up, mid afternoon, and before bed - I thought that was a good approach but maybe I should look into changing that. I’m waiting for some new blood test results so let’s see if they show anything ! I have 75mg T4 pills and 5mg T3 pills so it’s relatively easy for me to experiment

My heart rate can go low, below 50, if under or over medicated. Do you wear a fit bit or a sports watch. I was admitted to hospital once checking for bradycardia. I didn’t have bradycardia. I needed T3 medication along with Levothyroxine T4 at the time. Check your blood levels and see where you are at. Do you feel over or under medicated.

shaws profile image

Do you think you may be on a dose that maybe a little high?

Your daily dose is:-

150mg T4 and 30mg T3

25mcg of T3 is equivalent - in its action to 100 mcg of levothyroxine.

Your daily dose is approx more than 250mcg daily.

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