My fatigue scale would include:

"so tired that I am struggling to drink water/liquids"

"too tired to chew and swallow food"

"so tired that I am accidentally choking on/aspirating my own saliva because I am too tired to swallow saliva properly without paying attention" [for most people who are not exhausted, swallowing saliva safely is automatic. get exhausted enough, it stops being automatic]

And, yes, I hit all of those every month...