Not all bodies process caffeine the same.
Half the population are slow caffeine metabolisers and don't know it. Your genetics, age, and stress levels all change how coffee hits you, and how long it stays.
That's why we made five levels instead of two.
Fast or slow. It's in your genes.
The CYP1A2 gene controls how quickly your liver breaks down caffeine. Fast metabolisers clear it in hours and feel fine. Slow metabolisers can still have half a cup's worth circulating at bedtime, leading to restless sleep, racing thoughts, and morning fatigue they blame on everything except yesterday's coffee.
Age slows metabolism further. Hormonal changes, medication, and even stress levels shift your tolerance month to month. A dose that felt perfect at 25 might feel like too much at 40.
Why some people get jittery and others don't.
A second gene, ADORA2A, controls your adenosine receptors. Caffeine works by blocking adenosine, the molecule that makes you feel tired. But people with certain ADORA2A variants have receptors that react more intensely when blocked, triggering jitteriness, nausea, and a background hum of anxiety that others simply don't feel.
This is separate from metabolism speed. You can be a fast metaboliser who still gets jittery, or a slow metaboliser who feels calm but can't sleep. Two different genes, two different problems. That's why a single "regular or decaf" choice was never enough.
Still in your system at midnight.
Caffeine blocks adenosine, the neurotransmitter that tells your brain you're tired. That's great at 8am. Less great when the half-life of 5-6 hours means a 2pm coffee still has half its caffeine active at 8pm, and a quarter at 2am.
Beyond sleep, caffeine triggers your fight-or-flight response: elevated heart rate, higher blood pressure, and for many people a background hum of anxiety they've learned to live with. Reducing your dose even slightly can make a noticeable difference.
Find your level.
We blend caffeinated and decaf beans at precise ratios, so you know exactly how much caffeine is in every cup.
There is no universal dose.
Why five levels matter
Most coffee comes in two options: regular or decaf. But caffeine sensitivity isn't binary, it's a spectrum. Our five blends (0, 25, 50, 75, 100) help you work out which levels fit your body and your day. Start with the Calibration Kit to taste all five, then reorder the numbers you will actually use.