Caffeine in tea: green, oolong and black — how much of a lift is in your cup
Caffeine in tea is almost always there, but a cup holds less than coffee and the effect is gentler. Here is how much caffeine is in green tea, black tea and oolong, where L-theanine comes in and how many cups a day are considered reasonable.
Caffeine in tea is the main reason a cup of tea perks you up, but on average a cup of tea holds noticeably less of it than a cup of coffee. In Taiwan, China and Japan people drink tea all day, and many notice it gives steadier energy. There's an explanation: both the amount of caffeine and the makeup of the drink are different.
Caffeine in tea types: how much is in black and green tea?
On average, an 8-ounce (237 ml) cup of brewed black tea has about 47 mg of caffeine and green tea about 28 mg, while a cup of brewed coffee has about 96 mg (Mayo Clinic). Oolong usually falls between green and black (Caffeine Informer).
- The numbers vary a lot with the variety, amount of leaf, water temperature and steeping time.
- The longer tea steeps, the more caffeine ends up in the drink.
- Later infusions of the same leaves usually contain less caffeine.
Why does green tea have less caffeine?
Green tea is usually brewed with cooler water and steeped briefly, so less caffeine passes into the cup. If you brew it strong and long, the gap with black tea narrows.
That's why the idea that "green tea doesn't give you a lift" isn't quite right. It's gentler, but strong green tea in the evening can disrupt sleep just as much as black tea.
The same goes for pu-erh and other dark teas: they contain caffeine, and the amount depends on the leaf and how it's brewed. It's better to go by how you feel than by the numbers on the package.
Caffeine in tea vs coffee: what's the difference?
The main difference isn't only the amount of caffeine but L-theanine, an amino acid found in tea leaves. In a study combining caffeine and L-theanine, participants did better on attention tasks and reported feeling more alert (study on PubMed).
That's why many people describe tea's effect as "calm focus" and coffee's as a sharper boost. For how coffee affects sleep and how many cups are considered normal, see "Coffee and health".
Why does tea give a gentler lift than coffee?
Less caffeine per cup plus L-theanine — that's the whole secret. Tea is also usually sipped slowly, in small servings throughout the day, so the caffeine arrives gradually.
Another factor is habit. If you drink a lot of coffee every day, your body gets used to higher doses, and a cup of tea may barely register. That doesn't mean tea has no caffeine — the effect is just softer.
- A smaller dose means no sharp spike in alertness.
- L-theanine brings a sense of calm attention.
- Ritual: brewing and drinking tea is a pause in itself.
How many cups of tea a day is reasonable?
For most healthy adults, up to 400 mg of caffeine a day from all sources is considered safe (Mayo Clinic). But count everything together: tea, coffee, cola, energy drinks and chocolate.
If you feel a slump by late afternoon and crave something sweet, the issue may be your eating routine rather than tea. More on that in "Sugar and energy" and "Daytime energy without caffeine".
How to drink tea without disrupting sleep
Keep strong tea for the first half of the day, and choose caffeine-free herbal drinks in the evening. People who are sensitive to caffeine should watch how a late cup affects falling asleep.
Tea is a good ally, but energy comes from sleep, food and movement. Some people start the morning with the Cellergize Morning drink with vitamins and minerals (if you're pregnant, breastfeeding or taking medication, check with your doctor first), and during the day they choose Energy Enhancer — according to LifeWave, a patch for steady energy without caffeine. More in our article about Energy Enhancer.