Fitbit Blaze logging heart rate wrong

[Didge15]

so I have a fit-bit blaze, i upgraded from my 2014 polar fitness watch.... the first week it was great but I have been having so many issues with it that shouldn't be happening.  when I'm on the treadmill or doing weight the heart rate will drop out or be between 90-120 heart rate. For someone who is unfit and doing hiit it makes me mad. my treadmill comes with a polar strap for example  my heart rate read out was 193 (i was seating and out of breath!) my fit-bit read out was 116... I have reset it, turned it off and on removed the device and re-added it but nothing is working! It's pretty bad when the heart rate read out is 70+ beats of what it actually is... I went to take it back but (I had missed place my receipt) so nothing could be done. yes that's my fault. How do I fix my fit-bit blaze to work correctly? as someone who is over weight I rely on calories in and out. I really hope I get an answer soon as right now all its good for is telling the time! 

Moderator edit: Updated subject for clarity

[FerdinandFitbit]

Hi there @Didge15. Welcome to the Fitbit Community Forums! 🙂

I'm sorry to hear that your tracker is not being as accurate as you would expect and thanks a lot for what you have already tried to get it to work properly.

As with all heart-rate tracking technology, whether a chest strap or a wrist-based sensor, accuracy is affected by personal physiology, location of wear, and type of movement.

When you’re not exercising, wear your device a finger’s width below your wrist bone. Fitbit’s PurePulse heart-rate tracking system is designed to be most accurate when the device is worn on the top of your wrist.

For improved heart-rate accuracy keep these tips in mind:

1. Experiment with wearing the device higher on your wrist during exercise for an improved fit and more accurate heart-rate reading. Many exercises such as bike riding or weight lifting cause you to bend your wrist frequently, which could interfere with the heart-rate signal if the watch is lower on your wrist. 
   
2. Make sure the device is in contact with your skin.
3. Do not wear your device too tight; a tight band restricts blood flow, potentially affecting the heart-rate signal. That being said, the device should also be slightly tighter (snug but not constricting) during exercise than during all-day wear.
4. With high-intensity interval training, P90X, boxing, or other activities where your wrist is moving vigorously and non-rhythmically, the movement may prevent the sensor from finding an accurate heart rate. Similarly, with exercises such as weight lifting or rowing, your wrist muscles may flex in such a way that the band tightens and loosens during exercise. Try relaxing your wrist and staying still briefly (about 10 seconds), after which you should see an accurate heart-rate reading. Note that your device will still provide accurate calorie burn readings during these types of exercise by analyzing your heart rate trends over the course of the workout.

Hopeyou find this information helpful and if you need anything else, I'm here to help!