Black Tea

Medically Reviewed by Mahammad Juber, MD on September 21, 2022

Black tea is made from the leaves of a bush called Camellia sinensis. It has caffeine as well as other stimulants and antioxidants. Lots of people in the U.S. drink it either hot or cold. It should always be steeped in hot water before it is cooled.

A process called oxidation turns the leaves from green to a dark brownish-black color. Oxidation means the leaves are exposed to moist, oxygen-rich air.

Tea manufacturers can control the amount of oxidation. Black tea is a fully oxidized tea. Green tea comes from the same plant, but is not oxidized.

Black tea extract is sometimes sold as an herbal supplement. Sometimes, the supplement includes other types of herbs, vitamins, or minerals.

Many people drink black tea just because they like it. People also may use it for:

  • Alertness and energy
  • Antioxidants, including polyphenols and catechins
  • Possible anti-cancer effects
  • Heart health
  • Improved metabolism
  • Gut health

More research is needed, but there’s some evidence drinking black tea regularly may lower your risk for these conditions:

Drinking black tea in moderate amounts is generally safe for most people. There’s no known right amount to drink. Supplement ingredients and quality may vary widely. This makes it hard to set a standard dose.

Drinking large amounts of black tea -- more than four or five cups a day -- may cause health problems. That's mostly because of caffeine-related side effects.

Side effects of black tea (most often in high amounts) may include:

Combining black tea with other types of caffeine or a product called ephedra can be very dangerous. Some of the problems it can cause include:

  • Jitteriness
  • Increased blood pressure
  • Heart rate changes
  • Seizures
  • Passing out

Black tea or black tea supplements may interfere with other medicines and supplements you are taking. Some medicines can also cause caffeine to stay in your body longer than usual. Talk to your doctor to find out if any medicines you are taking may have this effect. The caffeine in black tea may also interfere with certain blood tests. Always tell your doctor about any supplements you are taking, including natural ones and those bought without a prescription. Let your doctor know if you drink a lot of black tea.

If you use supplements with black tea, keep in mind that the FDA does regulate dietary supplements; however, it treats them like foods rather than medications. Unlike drug manufacturers, the makers of supplements don’t have to show their products are safe or effective before selling them on the market.

Show Sources


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Hodgson, J.M. Molecular Aspects of Medicine, December 2010.

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Journal of Human Nutrition and Dietetics: “Impact of tea drinking on iron status in the UK: a review.”

Nutrients: “Tea compounds and the gut microbiome: Findings from trials and mechanistic studies.”

Journal of Taibah University Medical Sciences: “Influence of black tea on Streptococcus mutans and Lactobacillus levels in saliva in a Saudi cohort.”

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