Caffeine and you
Genetics, body weight, hormones, smoking, age: why the same cup does not do the same thing to two different people.
The same cup does not do the same thing to two people. How fast you clear caffeine varies several-fold between individuals, driven mostly by genetics, hormonal status, smoking and medication.
Body weight matters too, but not in the way most people assume: it dilutes the dose rather than changing the speed at which you clear it. Start with what sets your personal limit.
-
How much caffeine for your weight? The mg/kg rule
Caffeine works per kilogram of body weight, so 400 mg isn't universal. Here's how to work out your own reference — and why weight is only part of it.
-
Why are you so sensitive to caffeine?
If half a cup leaves you wired, you may be caffeine-sensitive. The two kinds of sensitivity — clearance and response — and the ADORA2A gene behind it.
-
Why doesn't coffee wake you up anymore?
If coffee barely registers, that's caffeine tolerance. Why it happens, why the sleep hit stays, and how to reset it without quitting.
-
Why can't you handle caffeine like you used to?
Coffee you slept through at 25 now keeps you up. It's mostly your sleep changing with age, not caffeine lingering longer — and here's how to adjust.
-
Can you drink coffee at night and still sleep?
Some sleep fine after an evening espresso — usually fast metabolizers or low responders. Why it happens, and the catch: sleeping isn't sleeping deeply.
-
Quitting smoking makes your coffee twice as strong
Smoking speeds up caffeine metabolism, so quitting can roughly double the caffeine in your blood — and the jitters get blamed on nicotine.
-
Why doesn't caffeine affect you?
Some people barely feel caffeine — usually tolerance, fast metabolism or their genes. But here's the catch: not feeling it doesn't mean your sleep is safe.
-
Do men and women process caffeine differently?
Yes — but it's hormones, not sex. The pill roughly doubles how long caffeine lasts and pregnancy slows it more. What changes, why, and what it means.
-
How long to build (or lose) caffeine tolerance?
Caffeine tolerance builds within days and firms up over 1–2 weeks — and a 1–2 week break resets it. The timeline both ways, and how to keep caffeine working.
-
How to cut back on caffeine without the headache
Cutting caffeine suddenly causes the headache — so taper gradually instead. Use half-caf and decaf to ease down, keep the coffee you love, and skip the pain.