I wanted to write about my personal experience with carnitine as treatment for ME/CFS. I'll try to apply some critical thinking as well. A few years ago I first tried carnitine injections. They appeared to work but were also painful and had to be given often which was inconvienent and unpleasant due to the high acidity of the liquid. Eventually I gave up because I wanted something that worked better with fewer downsides. Last year I started seriously taking carnitine again, in capsule form. I believe it might actually work, even though the effect is hard to quantify. I recognize that it can be difficult to distinguish fluctuations in the illness severity from the effect of a treatment. It appears to act as mild stimulant in the short term, while over long periods of time also improves mental and physical endurance, which is crucial for ME/CFS (at least for how I conceive of it). With carnitine, I seemed to be less fatigued and need fewer daytime naps and at the end of the day wasn't totally exhausted anymore just from doing the lightest activities. I also became more mentally capable of sticking with a project and finishing it, even if I had to pause for days or weeks in between (which might just be another indicator that I'm less fatigued and therefore able to comit to projects instead of the extreme exhaustion constantly forcing me to quit). I suspect it can also cause changes in light sensitivity of the eyes, as well as a feeling of mental overstimulation and irritability. When I stopped carnitine abruptly, I became more fatigued, reduced my activity levels again, had more daytime naps and also experienced a frequent and distinct sensation that I know precedes hypoglycemia along with constant hunger. Genetic carnitine deficiency disorders are associated with hypoglycemia and the abrupt withdrawal might result in a situation where the body is used to an increased intake of carnitine and suddenly finds itself with much less of it. It could also be that I stopped carnitine because I was becoming more ill and less capable of sticking to a plan (that of taking carnitine every day. I'm unfortunately so impaired that sticking to even simple plans that require consistence can be extremely difficult, borderline impossible). The side effects are I think a hint that it's really affecting my phyiology. Maybe they also help me understand better how I am without carnitine (although they are probably exaggerating the difference due to the withdrawal). Self-reported health can also be unreliable in that people forget how badly they actually were affected if the change was slow and gradual over a longer period. Is there some evidence that carnitine metabolism might be altered in ME/CFS and that supplementation could be helpful? Yes I think there is but it's not iron cast. I would certainly support a clinical trial that looks further into this.