Fatigue can and often occurs in episodes. This experience, while highly disrputive, can be spun to promote healing, as triggers are identified.
This article on the Kleine-Levin syndrome and its response to lithium provides some insight into the role of this important mineral, and implicitly others, in the generation of consistent energy. Since we know that mitochondria are at the core of energy production and it’s illness, then this information may apply to many mitochondrial conditions.
While a psychiatric dose was used here, as evidenced by the blood levels that are not attainable with nutritionally-dosed lithium, this article is simply a launching point for what will probably be an improvement in protcols for fatigue and related mitochondrial conditions.
A striking response to lithium in Kleine–Levin syndrome.2014