Green Tea: Energy, Caffeine, and Health Benefits
A 240 ml cup of green tea contains 28 mg of caffeine.
- 240 ml green tea = 28 mg caffeine; matcha (1 tsp) = 70 mg.
- Average caffeine half-life ≈ 5.7 hours; ~48% of a dose remains after 6 hours.
- A single 240 ml cup of green tea leaves ≈ 13 mg after 6 hours and ≈ 6 mg after 12 hours.
- FDA recommends ≤ 400 mg/day for healthy adults; pregnancy guidance ~200 mg/day; AAP discourages caffeine for adolescents.
How green tea provides energy
Green tea delivers gentle stimulation primarily from caffeine and modulates it with L-theanine, an amino acid that promotes relaxation without sedation. That combination typically produces milder, longer-lasting alertness than a coffee spike. The stimulant effect scales with dose: 28 mg produces less central nervous system stimulation than a 96 mg drip coffee cup.
Caffeine content in green tea and related brews
The standard dataset value for brewed green tea is 240 ml = 28 mg (11.7 mg/100 ml). Matcha is an outlier because you ingest the leaf: matcha (1 tsp) = 70 mg per 240 ml. For context, other common tea values are 240 ml black tea = 47 mg and 240 ml white tea = 16 mg. Brewing time, leaf quantity, water temperature and leaf type change those numbers: longer steep and more leaf raise caffeine.
How green tea compares to coffee, tea and energy drinks
Below is a concise comparison using dataset values so you can judge energy per serving.
| Drink | Serving | Caffeine (mg) |
|---|---|---|
| Green tea | 240 ml | 28 mg |
| Matcha (1 tsp) | 240 ml | 70 mg |
| Black tea | 240 ml | 47 mg |
| Drip coffee | 240 ml | 96 mg |
| Cold brew | 240 ml | 200 mg |
| Espresso (single) | 30 ml | 63 mg |
| Red Bull | 250 ml | 80 mg |
| Bang energy | 473 ml | 300 mg |
| Coca‑Cola | 355 ml | 34 mg |
Caffeine metabolism: timing, half-life and concrete decay
Population-average caffeine half-life is about 5.7 hours. For practical planning use the common decay fractions: after 3 h ≈ 69% remains, 6 h ≈ 48%, 9 h ≈ 33%, 12 h ≈ 23%.
| Start dose (mg) | 0 h | 3 h (~69%) | 6 h (~48%) | 9 h (~33%) | 12 h (~23%) |
|---|---|---|---|---|---|
| Green tea (240 ml) | 28 mg | 19 mg | 13 mg | 9 mg | 6 mg |
| Matcha (1 tsp) | 70 mg | 48 mg | 34 mg | 23 mg | 16 mg |
Practical takeaway: a single cup of green tea leaves only trace caffeine by bedtime if you stop 6–8 hours before sleep, but individual sensitivity varies.
Can green tea keep you awake?
Yes—green tea can keep some people awake. At 28 mg per 240 ml it’s low compared with coffee, but people who are caffeine-sensitive, pregnant, anxious, or taking stimulants can notice wakefulness from a single cup, especially late in the day. For many adults the mild dose will not disrupt sleep if consumed earlier in the afternoon.
Green tea and weight loss: what the evidence says
Green tea contains caffeine plus catechins (notably EGCG) that modestly increase energy expenditure and fat oxidation in some trials. The effect size is small—measured as a few additional kcal burned per day—and works best combined with diet and exercise. Regulatory agencies such as EFSA have evaluated catechin safety; benefits are modest and not a replacement for calorie control.
Supplements, extracts and safety limits
Green tea extract concentrates caffeine and catechins; a cup-equivalent label can underrepresent active dose. Compare: a caffeine pill is 200 mg, many pre-workouts list ~150–200 mg. FDA guidance: healthy adults ≤ 400 mg/day; pregnancy guidance often cites ~200 mg/day. The American Academy of Pediatrics discourages caffeine for adolescents. Combining multiple sources (tea, coffee, energy drinks, pills) raises overdose risk—track intake with an app like CoffeeLog to avoid exceeding limits.
Practical recommendations and medical caution
If your goal is gentle daytime focus, 1–3 cups of green tea spread through the morning gives steady alertness with lower jitter risk than coffee. Avoid green tea within 6–8 hours of bedtime if you're sensitive. If you are pregnant, breastfeeding, have arrhythmia, anxiety disorders, or take medications, consult your clinician—this page is informational, not medical advice.
Where to track and next steps
To see how green tea fits into your daily caffeine budget, log servings and timing. CoffeeLog can automatically sum heterogeneous sources (tea, coffee, energy drinks, pills) so you can compare intake to FDA and pregnancy guidance and observe effects on sleep.
Authorities referenced: USDA FoodData Central (standard beverage values), FDA (daily upper limit guidance), EFSA (catechin safety reviews), Mayo Clinic (caffeine effects summary), American Academy of Pediatrics (adolescent guidance).
Frequently asked questions
Can green tea keep you awake?
Yes. A 240 ml cup contains 28 mg of caffeine—low but sometimes enough to delay sleep for sensitive people; stopping intake 6–8 hours before bedtime usually prevents disruption.
How much caffeine is in matcha?
Matcha (1 tsp in 240 ml) contains about 70 mg of caffeine, roughly 2.5× a brewed green tea cup and closer to a weak coffee in stimulant effect.
When should I stop drinking green tea before bed?
For most adults, stop 6–8 hours before bedtime. With a 28 mg cup, about 13 mg remains after 6 hours and about 6 mg after 12 hours; sensitivity varies.
Is green tea effective for weight loss?
Green tea can modestly increase energy expenditure and fat oxidation, but effects are small—useful as a complement to calorie control and exercise, not a standalone solution.
Is green tea safe during pregnancy?
Pregnancy guidance typically recommends limiting caffeine to about 200 mg/day. One 240 ml green tea cup (28 mg) fits well under that limit, but combine totals from all sources and consult your clinician.
How does green tea compare to coffee for steady energy?
Green tea (28 mg) produces milder, longer-lasting alertness—especially with L-theanine—whereas drip coffee (96 mg per 240 ml) gives a faster, stronger stimulant effect and larger sleep disruption risk.