Image source: Fitbit

Users are reporting inaccurate heart rate on Fitbit Sense. Is there a fix?

Quite a few Fitbit Sense users are reporting issues with heart rate tracking during exercise. These range from lags in reporting to wildly inaccurate readings. There’s clearly an issue. In this article we cover some common fixes for the problem.

All of this was first reported on Fitbit Community forums. In fact, there are multiple threads discussing inaccurate heart rate tracking on Sense. One of these has grown to more than 400 responses! You won’t find many larger threads on the forums. If you visit the Sense community pages you’ll notice that it is probably the thing most people complain about.

Users are not really reporting too many problems with resting heart rate or during low intensity activities. It is with exercise such as running, for example, weight lifting, cycling that the problems arise. Which kind of defeats the purpose of having a fitness tracker.

Particularly as you can’t pair a Fitbit to an external heart rate monitor such as a chest strap or armband. And Fitbit has not said anything about plans to produce a chest strap of their own. Which is a shame because that would resolve all the issues. Such devices are not affected by hand and arm movements that have an impact on watch heart rate accuracy.

Typically, users are reporting that the readings during intense exercise are too low.

“My heart rate comes and goes. Ill be doing an interval training where my heart is beating out of my chest and the watch says I’m under zone. Funny thing is I get off the machine and walk a few steps and the rate shoots up!” one users writes.

“I’m sorry to say but my opinion is that Sense heart rate sensor is practically a generator of random numbers.” is an ever harsher response of another!

“I’m in a university study. They strap a polar heart monitor on me. And while the polar says 120 bpm my Fitbit sense is at  about 83.  Wasn’t expecting that big of a difference.” concludes another.

Interestingly enough, the problem doesn’t appear on other Fitbits such as the Versa, Charge, Inspire range or Luxe. At least not to the same extent. Heart rate tracking from the wrist is not yet on par with tracking with an external heart rate chest strap. But it should be close. So what’s going on with Sense?

Fitbit has not officially addressed the problem. And there clearly is one. But one user has posted a reply she received from the Team – “Thanks for letting us know about this issue. We’re aware of it and are working to identify a resolution as quickly as possible.”

So the company is obviously aware there’s something going on. Which means there might be nothing you can do right now to resolve. Hopefully a fix will follow soon via a firmware update, as there may be a bug in the software. We doubt that the cause is the hardware – the heart rate sensor that can be found in Sense can also be found in other Fitbits.

Which currently leaves us with common fixes for the problem – hopefully, one of these will work for you.

But let’s start with the basics.

How do I track heart rate with my Fitbit?

Buying a Fitbit smartwatch or fitness tracker with a built-in heart rate sensor is a wise investment. Such devices can let you know your resting heart rate, perhaps the best indicator of the state of your health and fitness. Lower values are commonly associated with better cardiovascular health and even longer longevity.

Heart rate-enabled devices also allow you to heart rate zone train. Most elete athletes take advantage of this. It is because heart rate zone training allows them to reach their top potential in the shortest amount of time possible. It’s all about knowing hard hard you need to work your ticker during exercise for maximum effect.

Only a few years ago, fitness trackers with heart rate were few and far between. Now it has become the standard. Even low cost devices that will set you back $20-$30 come with built in heart rate sensors. The more sophisticated ones will even warn you if they spot irregularities in heart beats, or if your heart beat is too low or two high while resting.

You might be wondering how such devices measure heart rate. The wrist is a good place to take measurements. The wearable shines LEDs many times per second into your cappilaries. This is typically a green light but it could also be red or a combination of the two. Fitbit uses green LEDs. It also uses infrared light to determine when the wearable is sitting on your wrist.

The sensor utilizes light-sensitive photodiodes to detect how your capillaries move. They expand and contract based on blood volume changes. This allows them to calculate your heart beat per minute, typically referred to as bpm. Fitbits have the capability od detecting within a range between 30 and 220 bpm.

How to wear your Fitbit for most accurate heart rate tracking.

Probably the most important thing to know is this – in order to get a good read on your heart rate, you need to make sure you are wearing your Fitbit correctly. For day to day use, there’s nothing special you need to know. Wear your Fitbit as you would normally, just above your wristbone.

With exercise there are increased movements of your wrist. Plus there could be some slippage. To get an accurate reading you need to make sure the device is snug with good skin contact. But don’t make the mistake of wearing it too tight as this might constrict blood-flow.

Fitbit also suggests when exercising to wear the device a finger’s width above your wrist bone. That’s because device will move less in this position which should ensure more accurate readings.

Why is my Fitbit not tracking heart rate?

But even with this, heart rate tracking can struggle in certain conditions. Fitbit lists a few of these such as air temperature, stress level, alcohol or caffeine intake, immune response to illness and medication use. For example, exercising in cold weather can make it more difficult to track heart rate. This is because the cold air can affect the amount of blood that flows through your skin. There’s nothing really you can do about any of this.

And that’s pretty much it. You can’t do much more than ensuring that you are wearing the device correctly. The only other thing you should do from time to time is clean the underside of the device. That’s because there could be sweat, dirt and grime accumulating which might impede with the heart rate sensor. This should be done with fresh water and a sop-free cleanser. Simply wipe way any dirt. Don’t make the mistake of using any the of soap or sanitizer or household cleaner.

Other common heart rate problems with Fitbits

Why is my Fitbit not tracking my heart rate?

Sometimes things go wrong and the otherwise trusty device on your wrist stops tracking heart rate and the lights below on the sensor don’t flash. Here’s what to do.

Essential readingTop fitness trackers and health gadgets

Whenever you experience a problem with a Fitbit device, the first thing to do is to give it a good old restart. This is the go-to solution if the screen on your wearable is unresponsive, if it’s not connecting to the app or if it is not tracking your activity. If you’re not sure how to do this, check out our guide on how to reset your Fitbit fitness tracker or smartwatch.

This may or it may not solve the problem. If it didn’t work the first time around, it’s worth trying 2 or 3 times before giving up.

The next thing you can do is charge the battery to full capacity. This is because the heart rate tracking problem may appear if the battery is critically low as the sensor may switch off automatically.

Make sure heart rate tracking is switched on!

It may seem kind of obvious, but also double-check that you have heart rate tracking switched on! Fitbit switches this on by default but perhaps you turned it off.

On smartwatches check by opening the Settings app on the watch and tweaking the option to “On” (“On” or “Auto” for Blaze) . For Alta devices and early generations of Charge, make sure the heart rate setting is set to “Auto”.

What to do if heart rate on your Fitbit is grey, blank or frozen

If the heart rate reading on your watch is greyed out, blank or frozen – the device probably does not have a strong signal. This sometimes happens if you are moving your arm vigorously.

Give the tracker a few seconds to obtain a better reading. Things should revert to normal after that. A greyed out reading is an indicator the Fitbit is looking to secure a stronger signal.

Why is my Fitbit not tracking heart rate?

Other tips

Hopefully one of these solutions has fixed your problem. If you’ve tried all the steps in this article and nothing is resolving the issue with heart rate tracking, you might want to try restarting your Fitbit. This is the go-to solution for many problems. The final alternative is that your device may be faulty. It’s best to contact Fitbit Customer Support if you suspect this is the case.

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Marko Maslakovic

Marko founded Gadgets & Wearables in 2014, having worked for more than 15 years in the City of London’s financial district. Since then, he has led the company’s charge to become a leading information source on health and fitness gadgets and wearables.

6 thoughts on “Users are reporting inaccurate heart rate on Fitbit Sense. Is there a fix?

  • Why does my Fitbit inspire have two hearts -the second one is resting BPM- what’s the first one BPM?

  • I’ve used Fitbit devices for several years (Ionic, Versa, Versa2) never had problems. I switched to Sense about 6 months ago and the heart rate is completely off! My heart can be pounding at 160 bpm but Sense shows 118. Really annoying as I primarily use it for fitness tracking. And, dear Fitbit customer support, I know how to wear it and I use it in normal conditions indoors. The problem is the product not all the people reporting there’s a problem with it.

  • Just received my Sense. Wearing it to the Gym I find the heart rate is totally incorrect compared to my four-year-old Versa. Comparing the exact workouts using my Versa and Sense shows totally different Caloric and heart rate numbers which are related to heart rate. A specific exercise will show a much lower heart rate 0n the Sense then on my old Versa. Is rher a fix coming?

  • I have a Fitbit Sense and have noticed my HR so varies. Shoots up at work to 150 from 70. I have stressful job , but never noticed with old Fitbit .

  • Just purchased a new Fitbit Sense a few days ago. I have been a fitbit user for seven years. I like the watch, but the heart rate tracking is way off compared to my previous devices. It sounds like this problem has been around awhile. Does anyone know of a fix?

  • Yup. SAME issue as all of the other reports. I’m an avid HR tracking dude, and I wear a Polar RS-200 with chest strap, and it is very accurate. My Sense reports a heart rate 20 – 30 bpm LOWER than what it really is … especially at higher exercise levels. YES, I wear it correctly. Yes, I’m indoors. I’m on an Elliptical. Even the heart rate monitor built into the Elliptical is more accurate than the Sense (but less accurate than the Polar).



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