Even a tiny coffee makes me anxious and jittery

A gene called ADORA2A controls how sensitive your brain's receptors are to caffeine, so some people feel jittery on a dose that barely registers for others.

Why it happens

Caffeine works by blocking adenosine receptors. If your ADORA2A variant makes those receptors especially responsive, even a small coffee can spike your heart rate and tip you into anxiety. This is separate from how fast you clear caffeine, you can be sensitive even as a fast metaboliser.

One thing to try

Try half your usual dose tomorrow, or switch to green tea. Sensitivity often responds to amount more than you would expect.

Each decode is a research-backed tendency, not a diagnosis. A tap tells you how your body is likely wired and what to try, it does not label you, and nothing here is a substitute for a doctor where a medical question is involved.