a quick and easy way for a doctor to irritate an ME patient is to ask 'how is your fatigue'. It gets a consultation off to a poor start, they expect a short simple answer which demonstrates a complete lack of understanding of the disease, and I have to supress my irritation, because I go to the consultation trying to get something other than an argument.
That may be more to do with the fact that ME/CFS patients are easily irritated.
The question of what ME/CFS fatigue is like is a perfectly straightforward and fair one, asked by an interested party, so hopefully people will be able to articulate it.
My answer is the following. Obviously the severity of ME/CFS can vary considerably from patient to patient. ME/CFS is labelled mild, moderate, or severe, and so the depth of fatigue felt will vary accordingly.
A few years ago, my ME/CFS was at the moderate to severe level, and on bad days when my fatigue was at the maximum, it felt like I was just about to expire and leave this body for the next life. It felt that all your life energy had gone, and you were about to expire and die. It is not at all an unpleasant feeling, though, at least for me. It is actually quite beautiful feeling, as if you are about to give up the ghost. In this state, I was always reminded of stories I had read of people close death, like for example drowning, where there becomes an acceptance of death. In these times of extreme fatigue, you almost feel like this, you feel like you are happily accepting the oncoming of death.
Of course, nobody drops dead from fatigue in ME/CFS, but the extreme mental and physical weakness makes you feel as if you might. Usually when I would get to these severe levels of fatigue, I would soon fall asleep, and spent the most part of the day asleep. I would also sleep for 12 to 14 hours at night as well. Not all days were this bad though. I would only get say one or two days like this per week.
Though in the daily experiences of ME/CFS, the symptom of fatigue is closely intertwined with the other major ME/CFS symptoms, particularly brain fog and sound sensitivity, as these both tend to worsen considerably as fatigue levels increase.
Brain fog feels like some kind of dementia, where you are slow to comprehend the world around you. I know one story of an ME/CFS patient who forgot their name when asked for it by an official! That's how stupid you can (temporarily) become with brain fog. Another brain fog story was of a ME/CFS patient who could not figure out why her handbag was brim full with water. After many minutes of consternation, she finally figured out the reason: she had taken a shower just after returning home, and had forgotten to take off her coat and handbag before having the shower! With brain fog, you often have to laugh at your own stupidly.
Brain fog tends to get worse with increased fatigue, so alongside the fatigue, you can simultaneously feel "out of it" in this dementia-like way as a result of the increased brain fog.
Talking and making conversation is particularly hard under fatigue conditions. You don't seem to have the energy to put sentences together. So your replies are often reduced to one word answers, or even just grunts.
Sound sensitivity, which is one of the more unpleasant symptoms of ME/CFS, may also get worse under increased fatigue. Sound sensitivity is hard to explain, but if you have ever heard the scrapping sound of a fingernail on a blackboard when the chalk breaks, and noted how that scrapping sound is extremely grating and gets "under the skin", well, that's how many ordinary sounds feel like with ME/CFS sound sensitivity. Somehow in ME/CFS, sounds seem incredibly amplified in the mind, and seem to penetrate into the inner sanctum of the mind, which is mentally painful.
And the (for me embarrassing) emotional sensitivity and frailty often found in ME/CFS, where patients for example will find it example very stressfully and disturbing to listen to ordinary mild disagreements between people, this emotional sensitivity may get worse when there is increased fatigue.
So fatigue as a symptom does not occur in isolation, but is combined with the worsening of these various other mental and cognitive symptoms of ME/CFS.