How can I change my Health app profile picture on iPhone?

Your Health app profile picture is your Contact Card profile picture. Do you guys share an Apple Account? If so, you should not be doing that as Apple Account’s aren’t meant to be shared and each person should have their own.

Apple Support Article: Make sure that each family member has a unique Apple Account - Apple Support

Lawrence Finch’s User Tip: How to “unshare” an Apple ID - Apple Community

Kerib5 wrote:

My contact card shows my picture. I think this is a glitch that the health app has.

Another thing to try is a Force Restart.

• Press and quickly release the volume up button.
• Press and quickly release the volume down button.
• Press and hold the side button until you see the Apple logo 

Force restart iPhone - Apple Support

Kerib5 wrote:

I am not able to change the profile picture in the health app. It’s so weird. I can edit my info but I cannot change the picture.

You’ll need to change your Contact Card profile picture for it to also update in the Health app. So try updating your Contact Card profile picture.

Kerib5 wrote:

It didn’t help. Thanks anyway

If you want, you can proceed to Contact Apple for support and service - Apple Support.

Kerib5 wrote:

No, we do not share an Apple account, we both have different ID’s. I don’t know why his picture is showing up on my health account.

And have you tried changing it and see what happens?