When to stop drinking c4 energy
C4 Energy · 16 oz holds about 200 mg of caffeine. That's 2.1× an 8-oz brewed coffee — #13 of 78 drinks on this site, and about 50% of the 400 mg daily ceiling. Pick your bedtime and sensitivity; the cell is the clock time your last one starts — computed with a 5 h average half-life, and the calculator above adjusts live.
Finish your last one by
—
Your 200 mg over the next 16 hours
| Bedtime | Sensitive · 25 mg | Standard · 50 mg | Tolerant · 100 mg |
|---|---|---|---|
| 10:00 PM | 7:00 AM | 12:00 PM | 5:00 PM |
| 11:00 PM | 8:00 AM | 1:00 PM | 6:00 PM |
| 12:00 AM | 9:00 AM | 2:00 PM | 7:00 PM |
Source — CSPI caffeine chart (C4 Performance Energy, 16 oz), checked 2026-10-13.
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Common questions
When should I stop drinking c4 energy before bed?
For a 23:00 bedtime at standard sensitivity (50 mg bedtime limit), finish your last c4 energy by 1:00 PM. Sensitive readers should shift earlier; tolerant readers later.
Why do the times differ so much between people?
Caffeine half-life ranges 1.5–9.5 h across healthy adults, and dose differs by drink. The same can that clears a fast metabolizer by dinner can still be 50 mg in a slow one at midnight.
Method
Cutoff = bedtime − T½ × log₂(dose ÷ limit), base T½ 5 h, limits 25/50/100 mg. Every cell is computed, not quoted — the cutoff calculator applies the same formula with your metabolism factors.