Apple Health draining battery following iOS 14 update
If you have a welltory app or other third party integration, check it’s not stuck in a loop.
Past that, here are some general ideas.
Consider ruling out a temporary backlog of data processing if you updated iOS  in the last 36 hours. If for some reason you think it’s stuck or taking too long, one force quit of the device and then a normal restart and observe things for 24 hours worked for me.  Also, be sure any app writing data or reading data are disabled / up to date. Health could just be the abusee if other apps are poking it too much or wrongly.
You can also always back up and restore if you think your device needs that.
I do not do this lightly, but there are cases when the saved application state for things like Photo processing, health app processing and others can get stuck.

Back up your device - you need to be ready to erase and reinstall, so be sure you have a solid backup or save important app data to the cloud and verify it.
One time - power down the phone cleanly. (Slide to power off)
Verify that the issue of high battery usage continues. Consider deleting other apps that interact with health / photos (you have a backup - this is a short term deletion).
Then force power off the device - https://support.apple.com/en-us/HT201412 - this discards all saved application state.
The device will start all the processes again - expect high CPU / high heat, high battery drain until the processes complete.
If you can’t wait any longer - erase the device entirely and do not restore the backup.

Now - be sure the energy is low / the OS is good, and it idles properly - now do the erase / restore to get your apps and data back. Also, be sure to get any updates - X.0 releases are tested very well, but often without lots of live data - so it’s almost always the data we bring to the update that reveals bugs - not that an empty phone on X.0 release is buggy.
The only solution is to not update the first 2 weeks of a new release and let others find / report / triage / isolate these situations.