How long does Red Bull
stay in your system?

A standard 8.4 oz Red Bull contains 80 mg of caffeine, less than a typical mug of coffee. The sugar-free version has exactly the same caffeine; the difference is only the sugar. The taurine and B-vitamins on the label do not change how the caffeine itself is cleared from your body.

From 80 mg, the 5-hour half-life leaves about 40 mg after five hours and 20 mg after ten. A single can taken in the early evening will have mostly cleared by the next morning, though slow metabolizers and back-to-back cans extend that window considerably.