How to use Apple Watch for medical monitoring?

The Apple Watch is no medical device, but you can share data from your Health app:

Share and view health data in the Health app - Apple Support

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Not a medical device. Apple Watch is not a medical device and should not be used as a substitute for professional medical judgment. It is not designed or intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of any condition or disease. Please consult your healthcare provider prior to making any decisions related to your health.

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copied from: Important safety information for Apple Watch - Apple Support

Ask your physician for what is appropriate for your particular monitoring needs, or for the needs of the person you are considering this for.

Having used medical monitoring devices (3-and 12-lead cardiac monitors, pulse oximeters, sphygmomanometers, etc) a whole lot, an Apple Watch is not particularly comparable. There are uses, but there are also limits.

And fall detection isn’t going to pick up all falls. I’ve experienced both missed falls, and false fall detections.

If considering this for another person, also consider whether that person will be able to keep the Watch charged, and watchOS and the iPhone updated, and can see and operate the display. Not everybody can.

If you can be more specific, we may be able to offer more specific advice.

Monitoring what specifically, and for what purpose?