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Black tea is a product made from the Camellia sinensis plant. The aged leaves and stems are used to make medicine. Green tea, which is made from fresh leaves of the same plant, has some different properties.

Black tea is used for improving mental alertness as well as learning, memory, and information processing skills. It is also used for conditions such as headache, both low and high blood pressure, preventing Parkinson disease, and many others, but there is no good scientific evidence to support these uses.

In foods, black tea is consumed as a hot or cold beverage.

Black tea contains 2% to 4% caffeine, which affects thinking and alertness, increases urine output, and may reduce the symptoms of Parkinson disease. It also contains antioxidants and other substances that might help protect the heart and blood vessels.

When taken by mouth: Drinking moderate amounts of black tea is LIKELY SAFE for most adults.

Drinking too much black tea, such as more than five cups per day, is POSSIBLY UNSAFE. High amounts of black tea can cause side effects due to the caffeine in black tea. These side effects can range from mild to serious and include headache, nervousness, sleep problems, vomiting, diarrhea, irritability, irregular heartbeat, tremor, heartburn, dizziness, ringing in the ears, convulsions, and confusion. Also, people who drink black tea or other caffeinated beverages all the time, especially in large amounts, can develop psychological dependence.

Drinking very high amounts of black tea containing more than 10 grams of caffeine is LIKELY UNSAFE. Doses of black tea this high might cause death or other severe side effects.

Special Precautions & Warnings:

Pregnancy and breast-feeding: If you are pregnant or breast-feeding, drinking black tea in small amounts is POSSIBLY SAFE. Do not drink more than 2 cups a day of black tea. This amount of tea provides about 200 mg of caffeine. Consuming more than this amount during pregnancy is POSSIBLY UNSAFE and has been linked to an increased risk of miscarriage, increased risk of sudden infant death syndrome (SIDS), and other negative effects, including symptoms of caffeine withdrawal in newborns and lower birth weight.

If you are breast-feeding, drinking more than 3 cups a day of black tea is POSSIBLY UNSAFE and might cause your baby to become more irritable and have more bowel movements.

Children: Black tea is POSSIBLY SAFE when taken by mouth by children in amounts commonly found in foods.

Anemia: Drinking black tea may make anemia worse in people with iron deficiency.

Anxiety disorders: The caffeine in black tea might make these conditions worse.

Bleeding disorders: There is some reason to believe that the caffeine in black tea might slow blood clotting, though this hasn't been shown in people. Use caffeine cautiously if you have a bleeding disorder.

Heart problems: Caffeine in black tea can cause irregular heartbeat in certain people. If you have a heart condition, use caffeine with caution.

Diabetes: The caffeine in black tea might affect blood sugar. Use black tea with caution if you have diabetes.

Diarrhea: Black tea contains caffeine. The caffeine in black tea, especially when taken in large amounts, might worsen diarrhea.

Seizures: Black tea contains caffeine. There is a concern that high doses of caffeine might cause seizures or decrease the effects of drugs used to prevent seizures. If you have ever had a seizure, don't use high doses of caffeine or caffeine-containing supplements such as black tea.

Glaucoma: Drinking caffeinated black tea increases the pressure inside the eye. The increase occurs within 30 minutes and lasts for at least 90 minutes.

Hormone-sensitive condition such as breast cancer, uterine cancer, ovarian cancer, endometriosis, or uterine fibroids: Black tea might act like estrogen. If you have any condition that might be made worse by exposure to estrogen, don't use black tea.

High blood pressure: The caffeine in black tea might increase blood pressure in people with high blood pressure. However, this doesn't seem to occur in people who regularly drink black tea or other caffeinated products.

Irritable bowel syndrome (IBS): Black tea contains caffeine. The caffeine in black tea, especially when taken in large amounts, might worsen diarrhea and might worsen symptoms of IBS.

Brittle bones (osteoporosis): Drinking caffeinated black tea can increase the amount of calcium that is flushed out in the urine. This might weaken bones. Don't drink more than 300 mg of caffeine per day (approximately 2-3 cups of black tea). Taking extra calcium may help to make up for calcium losses. Older women who have a genetic condition that affects the way they use vitamin D, should use caffeine with caution.

Adenosine (Adenocard)

Interaction Rating=Moderate Be cautious with this combination.

Black tea contains caffeine. The caffeine in black tea might block the affects of adenosine (Adenocard). Adenosine (Adenocard) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop drinking black tea or other caffeine-containing products at least 24 hours before a cardiac stress test.

Alcohol

Interaction Rating=Minor Be watchful with this combination.

The body breaks down the caffeine in black tea to get rid of it. Alcohol can decrease how quickly the body breaks down caffeine. Taking black tea along with alcohol might cause too much caffeine in the bloodstream and caffeine side effects including jitteriness, headache, and fast heartbeat.

Antibiotics (Quinolone antibiotics)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down caffeine to get rid of it. Some antibiotics might decrease how quickly the body breaks down caffeine. Taking these antibiotics along with black tea can increase the risk of side effects including jitteriness, headache, increased heart rate, and other side effects.

Some antibiotics that decrease how quickly the body breaks down caffeine include ciprofloxacin (Cipro), enoxacin (Penetrex), norfloxacin (Chibroxin, Noroxin), sparfloxacin (Zagam), trovafloxacin (Trovan), and grepafloxacin (Raxar).

Birth control pills (Contraceptive drugs)

Interaction Rating=Minor Be watchful with this combination.

The body breaks down the caffeine in black tea to get rid of it. Birth control pills can decrease how quickly the body breaks down caffeine. Taking black tea along with birth control pills can cause jitteriness, headache, fast heartbeat, and other side effects.

Some birth control pills include ethinyl estradiol and levonorgestrel (Triphasil), ethinyl estradiol and norethindrone (Ortho-Novum 1/35, Ortho-Novum 7/7/7), and others.

Cimetidine (Tagamet)

Interaction Rating=Moderate Be cautious with this combination.

Black tea contains caffeine. The body breaks down caffeine to get rid of it. Cimetidine (Tagamet) can decrease how quickly your body breaks down caffeine. Taking cimetidine (Tagamet) along with black tea might increase the chance of caffeine side effects including jitteriness, headache, fast heartbeat, and others.

Clozapine (Clozaril)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down clozapine (Clozaril) to get rid of it. The caffeine in black tea seems to decrease how quickly the body breaks down clozapine (Clozaril). Taking black tea along with clozapine (Clozaril) can increase the effects and side effects of clozapine (Clozaril).

Dipyridamole (Persantine)

Interaction Rating=Moderate Be cautious with this combination.

Black tea contains caffeine. The caffeine in black tea might block the affects of dipyridamole (Persantine). Dipyridamole (Persantine) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop drinking black tea or other caffeine containing products at least 24 hours before a cardiac stress test.

Disulfiram (Antabuse)

Interaction Rating=Moderate Be cautious with this combination.

Black tea contains caffeine. Concomitant use of disulfiram and caffeine can decrease clearance and increase the half-life of caffeine, increasing effects and risk of adverse effects (11840).

Ephedrine

Interaction Rating=Moderate Be cautious with this combination.

Stimulant drugs speed up the nervous system. Black tea contains caffeine. Caffeine and ephedrine are both stimulant drugs. Taking black tea along with ephedrine might cause too much stimulation and sometimes serious side effects and heart problems. Do not take caffeine containing products and ephedrine at the same time.

Estrogens

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down the caffeine in black tea to get rid of it. Estrogens can decrease how quickly the body breaks down caffeine. Taking estrogen pills and drinking black tea can cause jitteriness, headache, fast heartbeat, and other side effects. If you take estrogen pills limit your caffeine intake.

Some estrogen pills include conjugated equine estrogens (Premarin), ethinyl estradiol, estradiol, and others.

Fluconazole (Diflucan)

Interaction Rating=Minor Be watchful with this combination.

Black tea contains caffeine. The body breaks down caffeine to get rid of it. Fluconazole (Diflucan) might decrease how quickly the body gets rid of caffeine. This could cause caffeine to stay in to body too long and increase the risk of side effects such as nervousness, anxiety, and insomnia.

Fluvoxamine (Luvox)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down the caffeine in black tea to get rid of it. Fluvoxamine (Luvox) can decrease how quickly the body breaks down caffeine. Taking caffeine along with fluvoxamine (Luvox) might cause too much caffeine in the body, and increase the effects and side effects of caffeine.

Lithium

Interaction Rating=Moderate Be cautious with this combination.

Your body naturally gets rid of lithium. The caffeine in black tea can increase how quickly your body gets rid of lithium. If you take products that contain caffeine and you take lithium, stop taking caffeine products slowly. Stopping caffeine too quickly can increase the side effects of lithium.

Medications for depression (MAOIs)

Interaction Rating=Moderate Be cautious with this combination.

The caffeine in black tea can stimulate the body. Some medications used for depression can also stimulate the body. Drinking black tea and taking some medications for depression might cause too much stimulation of the body and serious side effects including fast heartbeat, high blood pressure, nervousness, and others.

Some of these medications used for depression include phenelzine (Nardil), tranylcypromine (Parnate), and others.

Medications for depression (Tricyclic Antidepressants)

Interaction Rating=Minor Be watchful with this combination.

Coffee contains chemicals called tannins. Tannins can bind to many medications and decrease how much medicine the body absorbs. To avoid this interaction avoid coffee 1 hour before and 2 hours after taking medications for depression called tricyclic antidepressants.

Some medications for depression include amitriptyline (Elavil) or imipramine (Tofranil, Janimine).

Medications for diabetes (Antidiabetes drugs)

Interaction Rating=Minor Be watchful with this combination.

Black tea might increase blood sugar. Diabetes medications are used to lower blood sugar. By increasing blood sugar, black tea might decrease the effectiveness of diabetes medications. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.

Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), chlorpropamide (Diabinese), glipizide (Glucotrol), tolbutamide (Orinase), and others.

Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)

Interaction Rating=Moderate Be cautious with this combination.

Black tea might slow blood clotting. Taking black tea along with medications that also slow clotting might increase the chances of bruising and bleeding.

Some medications that slow blood clotting include aspirin, clopidogrel (Plavix), diclofenac (Voltaren, Cataflam, others), ibuprofen (Advil, Motrin, others), naproxen (Anaprox, Naprosyn, others), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, warfarin (Coumadin), and others.

Mexiletine (Mexitil)

Interaction Rating=Minor Be watchful with this combination.

Black tea contains caffeine. The body breaks down caffeine to get rid of it. Mexiletine (Mexitil) can decrease how quickly the body breaks down caffeine. Taking Mexiletine (Mexitil) along with black tea might increase the caffeine effects and side effects of black tea.

Pentobarbital (Nembutal)

Interaction Rating=Moderate Be cautious with this combination.

The stimulant effects of the caffeine in black tea can block the sleep-producing effects of pentobarbital.

Phenothiazines

Interaction Rating=Minor Be watchful with this combination.

Black tea contains chemicals called tannins. Tannins can bind to many medications and decrease how much medicine the body absorbs. To avoid this interaction avoid coffee 1 hour before and 2 hours after taking phenothiazine medications.

Some phenothiazine medications include fluphenazine (Permitil, Prolixin), chlorpromazine (Thorazine), haloperidol (Haldol), prochlorperazine (Compazine), thioridazine (Mellaril), and trifluoperazine (Stelazine).

Phenylpropanolamine

Interaction Rating=Moderate Be cautious with this combination.

The caffeine in black tea can stimulate the body. Phenylpropanolamine can also stimulate the body. Taking caffeine and phenylpropanolamine together might cause too much stimulation and increase heartbeat, blood pressure, and cause nervousness.

Riluzole (Rilutek)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down riluzole (Rilutek) to get rid of it. Drinking black tea can decrease how quickly the body breaks down riluzole (Rilutek) and increase the effects and side effects of riluzole.

Stimulant drugs

Interaction Rating=Moderate Be cautious with this combination.

Stimulant drugs speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and speed up your heartbeat. The caffeine in black tea can also speed up the nervous system. Drinking black tea along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with black tea.

Some stimulant drugs include diethylpropion (Tenuate), epinephrine, phentermine (Ionamin), pseudoephedrine (Sudafed), and many others.

Terbinafine (Lamisil)

Interaction Rating=Minor Be watchful with this combination.

The body breaks down the caffeine in black tea to get rid of it. Terbinafine (Lamisil) can decrease how quickly the body gets rid of caffeine and increase the risk of side effects including jitteriness, headache, increased heartbeat, and other effects.

Theophylline

Interaction Rating=Moderate Be cautious with this combination.

Black tea contains caffeine. Caffeine works similarly to theophylline. Caffeine can also decrease how quickly the body gets rid of theophylline. This might cause increased effects and side effects of theophylline.

Verapamil (Calan, Covera, Isoptin, Verelan)

Interaction Rating=Moderate Be cautious with this combination.

The body breaks down the caffeine in black tea to get rid of it. Verapamil (Calan, Covera, Isoptin, Verelan) can decrease how quickly the body gets rid of caffeine. Drinking black tea and taking verapamil (Calan, Covera, Isoptin, Verelan) can increase the risk of side effects for caffeine including jitteriness, headache, and an increased heartbeat.

Warfarin (Coumadin)

Interaction Rating=Moderate Be cautious with this combination.

Warfarin (Coumadin) is used to slow blood clotting. Large amounts of black tea might decrease how well warfarin (Coumadin) slows blood clotting. Decreasing the how well warfarin (Coumadin) slows blood clotting might increase the risk of clotting. It is unclear why this interaction might occur. Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.

Bitter orange: Using bitter orange along with other products that contain caffeine, such as black tea, can increase blood pressure and heart rate in otherwise healthy adults with normal blood pressure. This could increase the risk of serious heart problems.
Caffeine-containing herbs and supplements: Black tea contains caffeine. Using it along with other herbs and supplements that contain caffeine might increase the risk of caffeine side effects. Natural products that contain caffeine include coffee, black tea, green tea, oolong tea, guarana, mate, and others.
Calcium: High caffeine intake from foods and beverages, including black tea, flushes calcium out of the body in the urine.
Cordyceps: Black tea contains caffeine. The body breaks down caffeine to get rid of it. Cordyceps might increase how quickly the body gets rid of caffeine. This might decrease the effects of caffeine.
Creatine: There is some concern that combining caffeine, an ingredient in black tea, with ephedra and creatine might increase the risk of serious harmful effects. There is a report of stroke in an athlete who consumed 6 grams of creatine monohydrate, 400-600 mg of caffeine, 40-60 mg of ephedra, and a variety of other supplements daily for 6 weeks. Caffeine might also decrease whatever benefit creatine might have on athletic performance.
Danshen: Black tea contains caffeine. The body breaks down caffeine to get rid of it. Danshen can decrease how quickly the body gets rid of caffeine. Drinking black tea and taking danshen might increase the risk of side effects for caffeine, including jitteriness, headache, and an increased heartbeat.
Echinacea: Black tea contains caffeine. The body breaks down caffeine to get rid of it. Echinacea can decrease how quickly the body gets rid of caffeine. Drinking black tea and taking echinacea might increase the risk of side effects for caffeine, including jitteriness, headache, and an increased heartbeat.
Ephedra (Ma huang): Ephedra and black tea are both stimulants. They speed up the central nervous system. Using them together might speed it up too much, increasing the risk of high blood pressure, heart attack, stroke, seizures, and death. Don't take black tea with ephedra or other stimulants.
Folic acid: Black tea might reduce the amount of folate that the body can absorb and use.
Genistein-containing herbs and supplements: Black tea contains caffeine. The body breaks down caffeine to get rid of it. A chemical called genistein can decrease how quickly the body gets rid of caffeine. Drinking black tea and taking genistein might increase the risk of side effects for caffeine, including jitteriness, headache, and an increased heartbeat.
Herbs and supplements that might slow blood clotting: Black tea might slow blood clotting. Using it along with other herbs and supplements that might also slow blood clotting could increase the risk of bruising and bleeding in some people. Some of these herbs include angelica, clove, danshen, garlic, ginger, ginkgo, Panax ginseng, and others.
Iron: Black tea might interfere with the body's ability to absorb iron. This probably isn't a problem for most people, unless they are iron-deficient. If this is the case, drink tea between meals rather than with meals to lessen this interaction.
Kudzu: Black tea contains caffeine. The body breaks down caffeine to get rid of it. Kudzu can decrease how quickly the body gets rid of caffeine. Drinking black tea and taking kudzu might increase the risk of side effects for caffeine, including jitteriness, headache, and an increased heartbeat.
Magnesium: Drinking large amounts of black tea can increase the amount of magnesium that is flushed out in the urine.
Melatonin: Black tea contains caffeine. Taking caffeine and melatonin together can increase melatonin levels. Caffeine can also increase natural melatonin levels in healthy individuals.

Iron-containing foods: Black tea might interfere with the body's ability to absorb iron. This probably isn't a problem for most people, unless they are iron-deficient. If this is the case, drink tea between meals rather than with meals to lessen this interaction.
Milk: Adding milk to black tea appears to reduce some of the heart health benefits of drinking tea. Milk might bind with the antioxidants in tea and keep them from being absorbed. However, not all research confirms this. More evidence is needed to determine just how important this interaction, if any, might be.

An 8-ounce serving of black tea provides from 40-120 mg of caffeine, the active ingredient.

The following doses have been studied in scientific research:

BY MOUTH:

  • For mental alertness: 1-3 cups of black tea containing 30-100 mg of caffeine.
  • For heart attack: At least 1 cup per day.
  • For ovarian cancer: At least 2 cups per day.

Black Leaf Tea, Camellia sinensis, Camellia thea, Camellia theifera, Chinese Tea, English Tea, Feuille de Thé Noir, Té Negro, Tea, Thé Anglais, Thé Noir, Thea bohea, Thea sinensis, Thea viridis, Theaflavin, Théaflavine.

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