How much caffeine is in a teabag?

In this brief guide, we are going to answer ‘how much caffeine is in a tea bag?’ also we will dive into what caffeine is and how much caffeine is in everyday used beverages.

How much caffeine is in a teabag?

In a black tea bag, we get about 40 – 50 milligrams of caffeine a cup. Similarly, green tea also contains around 33 milligrams of caffeine per cup. While herbal teas contain little to no caffeine at all per cup. Other teas contain per cup, in mg: Black decaffeinated: 2–5; Green, brewed or tea bag: 25–50; Oolong, brewed or tea bag: 21–64; White, brewed or tea bag: 15; Instant, prepared from powder: 33–64; Yerba mate, brewed or tea bag: 65–130 and Iced tea: 27–42 (1).

What is caffeine?

Caffeine is an alkaloid, a secondary plant metabolite, that is an antagonist of adenosine receptors: A1 and A2. Caffeine is a natural brain and central nervous system stimulant that helps one to be awake, alert and prevents the onset of tiredness. Caffeine is commonly found in tea, coffee, chocolate, soft drinks and also energy drinks. Caffeine is demethylated in the liver. The following metabolites are then produced: paraxanthine, theobromine, and theophylline. Half-life of caffeine in plasma is from 2.5 to 5.0 h (2).

How does caffeine work?

Once a caffeinated food or drink is consumed, it quickly gets absorbed into the bloodstream via the gut. It’s broken down into various compounds as it reaches the liver, where it starts affecting the activity of various organs particularly the brain.

This said caffeine blocks the effect of adenosine – a neurotransmitter that relaxes the brain and makes you tired as the day goes by making you want to sleep. By blocking these neurotransmitters you feel less tired.

Caffeine is absorbed completely and is metabolized mainly by the CYP1A2 isozyme of the hepatic microsomal cytochrome P450 system. Caffeine undergoes demethylation, resulting in paraxanthine, theobromine, and theophylline. Finally, caffeine metabolites are biotransformed by microsomal enzymes to methylxanthines, dimethyl and monomethyl uric acids, trimethyl and dimethylallantoin, and uracil derivatives, which are filtered by the kidneys and exit the body in the urine (1).

Caffeine may also increase brain activity by affecting other neurotransmitters like dopamine and norepinephrine (2).

This combined effect stimulates the brain and promotes a state of arousal, alertness and focus and. produces the same behavioral effects as classical psychostimulants, such as cocaine and amphetamine, mainly motor activation, arousal, and reinforcing effects.  Because of this caffeine is often known to be a psychoactive drug. Caffeine is the most consumed psychoactive drug in the world, with about 90% of the population (including children) in the United States regularly consuming caffeine-containing beverages or foods (2).

What are the factors that affect the caffeine content?

Following factors greatly affect the amount of caffeine in your daily cup of tea or any other beverage.

Type of tea leaf used

Three main types of tea, i.e., green, black, and oolong tea differ in manufacturing processes. For the production of green tea, freshly harvested leaves are rapidly steamed or pan-fried to inactivate enzyme polyphenol oxidase, thereby preventing fermentation and producing a dry, stable product. To produce black and oolong teas, leaves go through a fermentation process. The fermentation process causes oxidation of simple polyphenols to more complex condensed molecules which give black and oolong teas their characteristic colors and flavors. The extended fermentation lowers the polyphenol content and elevates the caffeine content. Black tea has 2–3 times more caffeine as compared to green tea (3).

Broken tea leaves, as found in tea bags, imparts more caffeine when brewed compared to whole leaves. This is because the broken leaves give better diffusion due to their increased surface area.

Amount of tea leaf used

The more tea is used the more caffeine will be released. Since tea bags provide a standard amount of tea leaf, the amount of caffeine is uniform. But if you are using loose tea then the desired caffeine levels can be adjusted by adding more or less of it.

Time taken to brew the leaves

The longer the brew time, the more caffeine is released.

The temperature of the water

It’s a known fact that the higher the temperature, the more efficiently the flavors are leached out. Similarly, the higher temp of hot water the more caffeine is released.

What is the caffeine content in different teas?

Commonly, there are 3 types of tea variety commercially available; black tea, green tea and white tea. All the types of teas are obtained from the same plant named Camellia sinensis, what sets them is the time of harvest and oxidation levels. The oxidation occurs during the fermentation process, in which simple polyphenols present in the green tea leaves are transformed into more complex polyphenols (3).

Black tea leaves are usually oxidized and are harvested later on while white and green tea leaves are harvested much earlier and usually are not oxidized. This oxidation leads to a bold and sharp flavor of black tea and a greater amount of caffeine too. During these processes the catechins (a group of natural polyphenols in green tea, accounting for its characteristic color and flavor) are converted to polymeric compounds, theaflavins and thearubigins, consequently decreasing the catechin content. Oolong tea is prepared by firing the leaves shortly after rolling to terminate the oxidation and drying the leaves. Normal oolong tea is considered to be nearly half as fermented as black tea. As a consequence of the fermentation, black tea has 2–3 times more caffeine as compared to green tea (3).

What is the caffeine content in most beverages? 

Following is the table that simply tells the amount of caffeine you get from everyday used beverages (1).

Beverages 8 ozMilligrams per cup
Black tea (237 ml)47 – 90 mg
Green tea (237 ml)20 -45 mg
White tea (237 ml)6 – 60 mg
*Yerba mate (237 ml)85 mg
Herbal tea (237 ml)12 mg
Energy drinks (240 ml)50 – 160 mg
Soft drinks (240 ml)20 – 40 mg
Espresso (240 ml)240 – 720 mg
Coffee (240 ml)102 – 200 mg
Cocoa beverage (240 ml)2 – 7 mg 
Chocolate milk (240 ml)2 – 7 mg

*Traditional South American tea

Fun fact – Matcha green tea is also most commonly consumed and highly caffeinated tea. A half spoon ( 1 gm) of serving provides around 35 milligrams of caffeine.

How much caffeine should you consume?

Both the USDA –  U.S. Department of Agriculture and EFSA – European Food Safety Authority have marked 400 mg of caffeine intakes as safe. That is equal to 2 -3 cups of coffee or more tea. Certain conditions tend to make people more sensitive to caffeine’s effects, as can some medications. In addition, if you’re pregnant, trying to become pregnant, or breastfeeding, or are concerned about another condition or medication, we recommend talking to your health care provider about whether you need to limit caffeine consumption. The FDA has not set a level for children, but the American Academy of Pediatrics discourages the consumption of caffeine and other stimulants by children and adolescents.

But it’s better to limit the intake to 200 mg of caffeine a day and the intake should be in the daytime so that you don’t compromise on your sleep.

Caffeine consumption is considered safe but you become habitual to it after continuous exposure.

Side effects linked with excess caffeine can range from anxiety, restlessness, tremors, irregular heartbeats and trouble sleeping (2).

Too much caffeine also promotes headaches, migraine and high blood pressure in some individuals. Also expecting ladies are often asked to limit or quit caffeine as it can easily cross the placenta and increases the risk of miscarriage or low birth weight.

Caffeine also affects the ability of some drugs especially antidepressants, it’s found to increase its workability.

Other FAQs about Tea that you may be interested in.

How much does a gallon of tea weigh?

What is the difference between boba and bubble tea?

What is the best way to make tea with tea bags?


In this brief guide, we have answered ‘how much caffeine is in a tea bag?’ Also, we have discussed what caffeine is and how much caffeine is in everyday used beverages.

Hope you found this helpful. Any questions or comments will be appreciated.


  1. de Mejia, Elvira Gonzalez, and Marco Vinicio Ramirez-Mares. Impact of caffeine and coffee on our health. Trends Endocrinol Metab, 2014, 25, 489-492.
  2. Ferré, Sergi. An update on the mechanisms of the psychostimulant effects of caffeine. J neurochem, 2008, 105, 1067-1079.
  3. Hayat, Khizar, et al. Tea and its consumption: benefits and risks. Crit rev food sci nutr, 2015, 55, 939-954.