Very low resting heart rate - what could be wrong!

Hello @bgellman and welcome to Mayo Connect. I see that you stopped taking a Vitamin D supplement because of a slow heart rate. Would you share the amount of Vitamin D you were taking each day and the length of time you had been using this dosage? Has your doctor ever tested your Vitamin D levels?

@bgellman You’re so right about how it’s a matter of paying attention. It’s only when I started wanting to nap so much and feeling dizzy that I thought maybe my new smartwatch wasn’t wrong. I went back through my smartwatch data and was shocked how low my average RHR had fallen since October. Getting a range of blood tests after that showed I wasn’t anaemic (which I initially thought might be the problem) but that I was low in Vit D. I was surprised as I spend several hours a day walking my dogs or gardening in the sun and I also eat Vit D rich food. It just wasn’t being absorbed. So with me I only started taking the Vit D after the problem started 🤷‍♀️

It would be nice to know what’s going on and be able to address it. I think I’ll re-examine my diet closely next

Hi Isadora! You said, "Yet suddenly ...", so when did that suddenly occur, and how were things before?

I was having some slow heart rates recently that I hypothetically assigned to my beta blocker pills possibly having a much larger dose than listed, most of my life I've had the opposite problem, too fast a heart rate (bradycardia slow, tachycardia fast).

So when mine goes under 60 I take note, and when it goes under 50 I wonder hey now. Though I've had no other symptoms. But I have a cup of tea for the caffeine, walk around a little, and see that it's responding at least slightly to both. About the time my last pill should be wearing off my heart rate returns to normal.

Gardening can involve some exertion, does that raise your heart rate?

Presume the rest of your blood panel is fine, including A1C and blood glucose, and you're not doing anything crazy about your diet?

Hope you find your answers.

@carbcounter Very interesting. After stopping being super fit my RHR ranged between 55-65. My Fitbit Versa 3 smartwatch died on me in October 2025 and it’s no longer being manufactured. After a week or so I got another brand which showed an average RHR between 45-50. I posted on reviews that I thought I either had a defective watch or the brand wasn’t good at tracking RHR! Then in early November I started feeling very tired and had the dizzy spells. My RHR dropped to between 37-42. I was due my 3 monthly cancer blood tests so had those done and they were all fine. My oncologist ordered a brain MRI to double check which was clear. He then added on a suite of other things (thyroid, anaemia, Vit D etc). Everything was fine except Vit D. My blood pressure is fine. I am due my next PET-CT scan in January.

My echocardiogram ordered by my GP has come back with moderate leaky valves but no action required other than another ultrasound to be run in 2 years. My GP has just sent me a text to book in to discuss all the results.

Lots, thanks to the comments on here, to discuss! Very appreciative.

Just wondering whether you all use smartwatches to help track your health?

I know they all say not to use the data as a medical diagnosis.

However since I started using a smartwatch I do find the data a useful canary in a coal mine. Do you find that too?

I to have Afib and my heart rate drops to 37 when I am resting. Most days I run an average heart rate of mid 50s to upper 60s if I am lucky. I am on 12.5 mg of Toprol XL and they are now trying to wean me off of it to figure out why my rate is so low. I have been on the Toprol for about 35 years. Most doctors are telling me that because I am on a beta blocker of Toprol that the heart rate of 37 is fine. I am a little concerned I do get dizzy sometimes, and short winded. I was recently at the ER and the Doctor Who saw me told me to just come off of the Toprol. My blood pressure runs high one day and low the next day. I’ve tried to come off the Toprol like they said and I got the shakes and started jittering so I had to take my 12.5. I also stay tired a lot and some days physically exhausted. I am concerned like you with the low heart rate. I do not have a pacemaker or anything else, but I am wondering if it would help?

@isadora2021 I do use a smart watch. Does your smart watch ever tell you when you try to do the EKG on it that it cannot take it because it is a poor recording? Mine does wake me up when my rate gets too low. A lot of times I feel as though I’m in a fear, but it will not show up on my watch. It will only show up as a poor recording

@cannon360 Thank you for sharing your history with a very low heart rate and similar side effects to those I’ve been experiencing. I’m so sorry to hear you’ve had trouble coming off your beta blocker.

It is so strange when the heart starts doing things it didn’t used to do and trying to figure out why and what can be done!

I’m looking forward to meeting with my GP and seeing where I go from here.

@cannon360 I think for some the Smart watch has become I source of just another ailment, anxiety. With every passing moment of precieved strange heartbeat it becomes the " go to" source for a digital answer and we often find the answer to be just an opening of a door to another question without an answer.
Regarding the inconclusive reading look at it this way. With the watch you only have 2 physical contact points to take a reading. At a medical facility they stick you with multiple leads physically stuck to your skin to assure a valid reading. Which reading do you think is going to be a better reading?

The watch is a decent way to get some basic information but it provides more questions than answers and adds the little extra jolt of anxiety that I think most of us can have a much better life without.👍🏼

My resting heart rate in the 50 -55 range. I thought this is low too. I get dizzy sometimes too, Recently I visited Denver, Colorado and I had breathing difficulty and high heart rate and blood pressure too. Both went up to in the 145-149 range. I went to Emergency of the University of Colorado Hospital. They did not do any intervention. They said Denver is a high altitude place and this happens to some people. I returned back to Texas and heart rate went back to normal and blood pressure went down but it is now below 120. However, it used to be much lower. I saw a Cardiologist in Texas and they repeated the ECG test and did the Echo test and now they gave me a diagnosis of LeftBBB (left Bundle Branch Block). Now they want me to do Nuclear Echo test. I do not want to do this test because of risks involved. I read an article that there are two Ph.D doctors in Mayo Clinic in Minnesota who developed a noninvasive technique to deal with heart rhythm issues. If you are interested I can send you a copy of the article if you leave your email or phone.
I also made an appointment with a Holistic Cardiologist in January. I want to find out what her opinion is about this.
Just an idea, you may also try to talk to an Holistic Cardiologist as well. BTW I am 78 year old health concious woman, gardening and growing plants and outdoors are my hobbies too.