How to test whether ones body needs a substance? I want to test out Japanese knotweed and some other herbs as it can be hard with herx reactions.

1. You could try muscle testing using spooky, or muscle-test yourself. It's simple to learn, but takes a bit if practice.
https://www.spooky2-mall.com/blog/cat/spooky-pulse/post/muscle-testing/

2.In theory if you scanned the vitamins, using Min BPM settings, and something like a square wave (not InvSawtooth as in the Graded Scan), that should do it.

The only thing is that I find Max HRV works better.
So, say you apply vitamin K and your body, if it needs it, should respond by lowering the BPM - because it's being soothed and calmed. This is what it really needs!

This was discussed in a video featuring John White and David Bourke.
But I find that the body often responds to things it needs by increasing the BPM: saying yes, thank goodness, I really need this. At last! and up goes the BPM.

If the body does not need vitamin K, then there will be no or little response. Neutral.
So, for these kind of scans I use HRV and the Square wave, and it seems to work in picking up what the body needs.

For more details, please check the link:
https://www.facebook.com/groups/spooky2/permalink/838837509611487/