I sleep 10 hours a night but still need to nap constantly during the day. Even 400 mg of caffeine doesn't buzz me, it just makes me feel 70% close to my normal, high energy 20s self. My daytime fatigue is so severe I've been mistaken for being drunk (even though I don't drink), and I experience a dream like brain fog around friends unless I use caffeine pills to seem present.
I know this is part of normal aging for a woman in her 30s, but it's frustrating to constantly need naps when I haven't even done anything. Sometimes you just have to biohack. Still, I feel a bit jealous of how men age differently and seem to keep loads of energy.
What are your consumption habits, i.e. when are you drinking your caffeine? The bioactive halflife of caffeine is about 6-8 hours, so it's in your system affecting your mind and body long after the caffeine buzz goes away. My personal rule of thumb is all the caffeine I want before noon, but a hard cutoff at 1pm
I take my caffeine pills about an hour before I'm due to go out. Outings can be 8ish hours, but even when the caffeine is at peak amounts an hour after I take them they don't make me feel buzzed or hyper, just sort of close to normal. And this is at 400 mg.
If you're taking 400mg at noon, you'll have 200mg in your system at 6pm, and 100mg at midnight. 100mg+ in my system by bedtime will negatively and noticeably affect my sleep in those situations. You could be exhausted due to the time you're consuming caffeine
I only take caffeine pills occasionally. Not every day, and when I go through a long period of not having them I'm the same.