Black Tea: What Research Shows About the Tea, Safety and Cautions
Black tea as a drink: caffeine, brewing, what studies of the tea found, and cautions on iron absorption, kidney stones with very large amounts, pregnancy and very hot cups.
Content last updated . This page has not been medically reviewed.
Safety first. Natural products can cause side effects and interact with medicines. Read herbal tea and extract safety before you use anything on this page.
Check before you drink: black tea contains caffeine, so pregnancy, sleep and medicines matter [1][3][4]; it can make it harder to absorb iron from a meal [17]; and very hot drinks (above about 149 °F (65 °C)) are linked to esophageal cancer in the IARC review, so let a hot cup cool [19]. Black tea is a "true tea": it comes from the leaves of the tea plant, not from a herb. This page covers the drink itself and keeps it apart from capsules and extracts.
What black tea is
Black tea is made from the leaves of Camellia sinensis, the same plant that gives green, white and oolong tea. The teas differ mainly in how the leaves are processed after picking; black tea is a fermented type. [7] It is a true tea, not a herbal tea (tisane); see Herbal tea vs true tea. It contains caffeine. Most research on "tea" does not say which type was used, so we say so below whenever a study mixed black and green tea. For the supplement-level plant page see Green tea, and for a side-by-side look at the tea types see Green, black, white and oolong tea and the food page on black tea.Taste, caffeine and how to brew
| Question | What sources say |
|---|---|
| Taste | The sources we read do not describe taste. Black tea is commonly described as malty and full-bodied (a general description, not a sourced finding). |
| Caffeine per 8 fl oz (240 mL) cup | Sources differ. FDA lists 71 mg in a 12 fl oz cup of black tea, which is about 47 mg when scaled to 8 fl oz (our arithmetic). [4] Health Canada gives 30 to 50 mg per 8 oz cup of brewed black or green tea. [5] A US lab study of 20 commercial teas found 14 to 61 mg per 6 or 8 oz serving across white, green and black teas, with no clear pattern by tea type; steeping time changed the amount. [6] NHS estimates 75 mg in a cup of tea (black or green). [1] EFSA also lists a cup of black tea (220 mL) among common caffeine sources. [3] |
| Water temperature and steeping time | We found no official brewing instruction for black tea in the sources we read. In a lab study, tea was brewed at 176 °F and 212 °F (80 and 100 °C) for 2, 5 and 10 minutes; longer brewing raised the caffeine and L-theanine in the cup. [7] That is a research protocol, not advice. Industry sites are marketing, so we did not use them. |
| Amount of leaf per cup | Proper evidence not found in the sources we read for an official figure. |
| Cold brew or iced | Proper evidence not found in the sources we read. See cold brew and iced herbal tea safety for general storage points. |
| Very hot drinks | IARC classed very hot drinks (above about 149 °F (65 °C)) as "probably carcinogenic" to the esophagus and said it appears to be the temperature, not the drink, that matters. [19] See hot tea and esophageal cancer risk. |
Tea bags and loose leaf were compared for caffeine in the same lab study, but its abstract does not give a simple rule. [7] Bottled and sweetened teas are different products; the studies below were of plain tea.
What research found about the tea itself
Strength words: Promising but limited, Mixed, Insufficient evidence, Observational only.| Question | What the source found | Strength of evidence | Form and who was studied |
|---|---|---|---|
| LDL ("bad") cholesterol | A meta-analysis of 10 trials found LDL lower by 4.64 mg/dL (95% CI -8.99 to -0.30). Total and HDL cholesterol did not change clearly. The LDL effect was larger in people at higher heart risk. [8] | Promising but limited | Black tea drinkers in trials, 411 people |
| Blood pressure, people with high pressure | A meta-analysis of 5 trials (408 people) of green or black tea found systolic pressure down 4.81 mmHg and diastolic down 1.98 mmHg; after leaving out the most inconsistent trials, about 3.5 and 1 mmHg. Green tea looked stronger than black. [9] | Promising but limited | Green and black tea mixed, adults with elevated pressure |
| Blood pressure and cholesterol, short trials | A review of 14 trials (798 people, 4 to 24 weeks) of green or black tea found no significant effect on blood pressure or blood fats, and said trials were too small to be sure. [10] | Mixed | Green and black tea mixed, healthy and at-risk adults |
| High blood pressure in everyday drinkers | A 2026 meta-analysis of 20 observational studies (319,565 people) linked tea drinking to a modestly lower chance of high blood pressure, and the link was stronger for black tea drinkers in the cross-sectional studies. The authors say a protective effect cannot be confirmed. [12] | Observational only | Mostly questionnaires; tea types varied |
| Deaths | A meta-analysis of 38 cohort data sets (1.96 million people) linked the highest tea intake to 10% lower all-cause death and 14% lower heart-disease death; the cancer-death figure was not clearly lower (0.90, CI 0.78 to 1.03). The best results were around 1.5 to 2 cups a day. [11] A 2026 review adds that cause is uncertain, trials mostly measure markers, and genetic studies have not consistently backed a causal heart effect. [13] | Observational only | Tea types mostly not separated in the abstract |
| Thinking and mood | A meta-analysis of 50 trials looked at tea, theanine, and theanine plus caffeine. The clearest small effects were for theanine with caffeine, not for tea drinks, and the authors call for more research using actual tea beverages. [23] | Insufficient evidence for the tea itself | Healthy adults; mostly isolated compounds |
| Kidney stone risk factors | In 10 healthy men on a controlled diet, 1.5 liters a day of black tea for 5 days did not change urinary oxalate, and urinary citrate rose; the authors found no increased stone risk in healthy people. [14] | Insufficient evidence (small, short) | Black tea, 10 healthy men |
Limits. Many of these trials were short (weeks) and small, and several mixed green and black tea. Cohort studies compare people who choose to drink tea with people who do not, so they cannot show that tea causes the difference. We found no long trial of black tea on heart attack, stroke or cancer. For the same questions at the supplement level, nothing here applies to capsules or extracts.
Check before you drink
- Pregnancy and breastfeeding. NHS says to have no more than 200 mg of caffeine a day in pregnancy and estimates a cup of tea at 75 mg. [1] EFSA says caffeine from all sources up to 200 mg a day, spread through the day, does not raise safety concerns for the fetus, and gives the same figure for breastfeeding women. [3] Health Canada's recommended maximum in pregnancy is 300 mg a day, so official limits differ. [5] FDA advises people who are pregnant or breastfeeding to ask their provider whether to limit caffeine. [4] See pregnancy and breastfeeding and herbal teas to ask about in pregnancy.
- Babies and children. For children and teens EFSA proposes a safe level of 3 mg of caffeine per kilogram of body weight a day. [3] Proper evidence not found in the sources we read for black-tea-specific advice for babies. See herbal tea for babies and children.
- Caffeine and sleep. EFSA says a single 100 mg dose may affect sleep in some adults, especially near bedtime, and that up to 400 mg a day is not a concern for most healthy adults who are not pregnant. [3] FDA adds that people vary widely, and some conditions and medicines raise sensitivity. [4] See caffeine in teas.
- Medicines. The sources we read do not describe specific drug interactions for black tea as a drink (not described is not proof of none). FDA notes that some medicines raise sensitivity to caffeine. [4] Ask a pharmacist; see herbal tea and medicine interactions.
- Iron. In a study of adults, black tea cut absorption of iron from a bread meal by 79 to 94%, and adding milk made little difference. [17] NHS tells people with iron-deficiency anemia to have less tea and coffee, because large amounts make iron harder to absorb. [2] On the other hand, a French study of 2,593 adults found no link between tea drinking and blood iron stores (ferritin) in apparently healthy adults. [18] If you have low iron, ask a clinician about timing tea away from meals. See iron absorption and herbal tea.
- Kidneys and stones. Black tea contains oxalate. In an Iranian case-control study, people who drank 4 or more glasses a day had higher odds of calcium oxalate stones than those who drank fewer than 2 (odds ratio 2.73), though this shows association only. [15] A Taiwan study of 11,484 postmenopausal women found the opposite: habitual tea drinkers had fewer stones (OR 0.78). [16] The controlled trial above showed no rise in urinary oxalate. [14] Results disagree, so people with a history of stones or kidney disease should ask their clinician how much tea suits them. See liver and kidney cautions.
- Liver and allergy. The sources we read did not describe liver injury or allergy from drinking black tea. Not described is not proof of none.
- Very hot drinks. See the table above and hot tea and esophageal cancer risk. IARC's press release says the evidence is limited and that the proportion of cancers linked to very hot drinks is not known. [19]
- Fluoride and metals. A study of 121 black teas sold in Poland found fluoride varied by form and origin, with tea bags and teas from Africa highest; the authors say heavy drinkers or people in fluoridated areas could exceed recommended levels. [20] A second Polish study of 98 leaf teas judged leaf tea infusions not to pose a direct health risk, but said low-weight older women should moderate intake of high-fluoride teas. [21] A study of 8 black tea brands in Türkiye found metals were lower in the cup than in the dry leaf and within safety limits for typical drinking, with arsenic worth monitoring in a small sample. [22] These are single-country surveys; do not read them as results for every brand. See heavy metals in herbal tea.
Tea, capsule or extract?
A cup of black tea is a weak water extract of the leaf. Capsules and standardized extracts can hold different amounts of compounds, so a result for one form does not carry over to the other. We found no capsule or extract trials of black tea that we could read. For the supplement-level plant page see Green tea, and for how teas, tinctures and capsules differ see tea vs tincture vs capsule. Kombucha is a different, fermented drink made from tea; see kombucha.Buying and storing
- Check the label for the type (black tea), the origin and whether it is plain tea or a flavored blend; see reading an herbal tea label.
- Fluoride content differed between tea bags and loose leaf in one survey, so there is no single best form. [20]
- Storage and shelf life: see storing herbal tea. We did not find a sourced shelf-life figure for black tea.
Related pages
What research found and what to check: Black Tea
Findings about drinking the tea itself, kept apart from capsules, extracts and concentrated supplements. Each card says what was studied, in whom, and how strong the evidence is.
Black tea and LDL cholesterol
Preliminary or mixedA meta-analysis of 10 trials (411 people) found LDL cholesterol lower by about 4.6 mg/dL with black tea; total and HDL cholesterol did not change clearly. A later review of 14 short trials of green or black tea found no significant change in blood fats.
Supplements: Small effect in some trials; not a treatment. No capsule or extract trials read.
Black tea and blood pressure (trials versus cohort studies)
Preliminary or mixedTrials of green or black tea in people with raised pressure found small drops (about 3.5 to 4.8 mmHg systolic), but a review of 14 short trials found no significant effect. Cohort and cross-sectional studies link tea with a modestly lower chance of high blood pressure, which does not prove cause.
Supplements: Green and black tea were often combined; black tea looked weaker than green in one review.
Black tea, heart disease and deaths (observational)
Preliminary or mixedA meta-analysis of 38 cohort data sets (1.96 million people) linked the highest tea intake with 10% lower all-cause death and 14% lower heart-disease death, with the best results around 1.5 to 2 cups a day. Tea types were not separated and cause is uncertain.
Supplements: Association only. No long trial of black tea on heart attack, stroke or cancer was found in the sources read.
Black tea, oxalate and kidney stones
Preliminary or mixedBlack tea contains oxalate. A controlled trial in 10 healthy men (1.5 L a day for 5 days) did not raise urinary oxalate. A case-control study linked 4 or more glasses a day with more calcium oxalate stones, while a Taiwan study found fewer stones in habitual tea drinkers. Results disagree.
Supplements: Mixed; small trial and observational studies only.
Black tea and thinking or mood
Not enough evidenceA meta-analysis of 50 trials of tea, theanine and theanine plus caffeine found the clearest small effects for theanine with caffeine, not for tea drinks. The authors ask for more trials using actual tea.
Supplements: No good evidence for the black tea drink itself.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (3)
- Heart HealthPreliminary or mixed
Cohort studies link tea drinking with lower heart-disease death, and trials show small changes in LDL and blood pressure. Cause is not proven and short trials were mixed.
- Blood Pressure SupportPreliminary or mixed
Small drops in trials of green or black tea in people with raised pressure, but a review of short trials found none. Observational studies show a modest association only.
- Cholesterol BalancePreliminary or mixed
A meta-analysis of black tea trials found LDL lower by about 4.6 mg/dL; a later review of short green or black tea trials found no significant change.
Body systems (4)
- Cardiovascular SystemPreliminary or mixed
Same evidence as for heart and circulation: observational links and small, inconsistent trial changes.
- Heart & CirculationPreliminary or mixed
Observational links with lower heart-disease death and small trial changes in LDL and blood pressure; mixed and not proof of cause.
- Kidney & UrinaryPreliminary or mixed
Black tea contains oxalate; studies of tea and kidney stones disagree, with one controlled trial showing no rise in urinary oxalate and one case-control study linking 4 or more glasses a day to more stones.
- Sleep & RecoveryDocumented risk
Caffeine in black tea may disturb sleep in some adults, especially when drunk close to bedtime (EFSA).
Body parts (3)
- HeartPreliminary or mixed
Observational and small-trial findings for heart-related markers; not shown to prevent heart disease.
- Blood VesselsPreliminary or mixed
Small blood pressure changes in some trials of green or black tea; a review of short trials found none.
- KidneysPreliminary or mixed
Oxalate in black tea and mixed stone studies; very large amounts are the concern in case reports and association studies, results disagree.
Functional actions (1)
- Cardiovascular SupportPreliminary or mixed
Small changes in LDL and blood pressure in some trials; observational links with lower heart-disease death.
Root causes (1)
- Nutrient DeficiencyDocumented risk
Black tea strongly reduced iron absorption from a test meal; NHS advises less tea for people with iron-deficiency anemia. A study of healthy adults found no link with iron stores.
Biomarkers (2)
- IronDocumented risk
Black tea lowered iron absorption from a meal by 79 to 94% in a test; a French cross-sectional study of healthy adults found no link with ferritin.
- LDL CholesterolPreliminary or mixed
A meta-analysis of 10 black tea trials found LDL lower by about 4.6 mg/dL; a later review of short trials found no significant effect.
Conditions & symptoms (4)
- Iron DeficiencyDocumented risk
NHS advises people with iron-deficiency anemia to have less tea; black tea reduced iron absorption from a test meal. Healthy adults showed no link with iron stores.
- Essential HypertensionPreliminary or mixed
Small blood pressure drops in some trials of green or black tea; a review of 14 short trials found none; cohort links are observational.
- HypercholesterolemiaPreliminary or mixed
Black tea trials show LDL about 4.6 mg/dL lower on average; not a treatment, and a later review of short trials found no significant change.
- Kidney CalculiPreliminary or mixed
Studies disagree: a case-control study linked 4 or more glasses a day with more calcium oxalate stones, a controlled trial showed no rise in urinary oxalate, and a Taiwan study found fewer stones in tea drinkers.
Documented risks and interactions (4)
- Caffeine in black tea, sleep and pregnancy. Black tea contains caffeine. FDA lists 71 mg in a 12 fl oz cup, Health Canada gives 30 to 50 mg per 8 oz, and a lab study found 14 to 61 mg per serving across white, green and black teas. NHS and EFSA give 200 mg a day as the pregnancy figure; Health Canada gives 300 mg.
- Black tea and iron absorption. In adults eating a bread meal, black tea reduced iron absorption by 79 to 94%, and milk made little difference. NHS advises people with iron-deficiency anemia to have less tea. A French study of healthy adults found no link between tea drinking and iron stores.
- Very hot drinks and esophageal cancer. IARC classed drinking very hot beverages (above about 149 F / 65 C) as probably carcinogenic to the esophagus and said the temperature, rather than the drink, appears responsible. Tea is traditionally drunk very hot in some regions studied.
- Fluoride and metals in black tea. A Polish survey of 121 black teas found fluoride highest in tea-bag infusions and in teas from Africa, and said heavy drinkers or people in fluoridated areas could exceed recommended levels. A Turkish study of 8 brands found metals lower in the cup than in the dry leaf and within safety limits, with arsenic worth monitoring.
Frequently asked questions
How much caffeine is in black tea?
It depends on the leaf and the steeping. FDA lists 71 mg per 12 fl oz cup, Health Canada gives 30 to 50 mg per 8 oz, and a lab study found 14 to 61 mg per 6 or 8 oz across white, green and black teas. [4][5][6]
Is black tea safe in pregnancy?
It contains caffeine. NHS and EFSA both give 200 mg a day as the figure for pregnancy, while Health Canada gives 300 mg. [1][3][5] Ask your provider what suits you.
Does black tea lower blood pressure or cholesterol?
Some trials found small drops in LDL cholesterol and blood pressure, but a review of short trials found no significant effect, so the evidence is mixed. [8][9][10] Large cohort studies link tea with lower death rates, which does not prove cause. [11]
Can black tea cause kidney stones?
Results disagree. One case-control study linked 4 or more glasses a day with more calcium oxalate stones, while a controlled trial and a large survey did not. [14][15][16] If you have had stones, ask a clinician.
Does black tea stop me absorbing iron?
In a meal study it strongly reduced absorption of iron from the meal, and NHS advises people with iron-deficiency anemia to drink less. [2][17] A French study of healthy adults found no link with iron stores. [18]
References
- NHS (UK). Foods to avoid in pregnancy. Last reviewed 15 June 2026. Read 2026-10-23.
- NHS (UK). Iron deficiency anaemia. Last reviewed 26 January 2024. Read 2026-10-23.
- European Food Safety Authority (EFSA). Caffeine: EFSA explains risk assessment. 2015. Read 2026-10-23.
- U.S. Food and Drug Administration. Spilling the Beans: How Much Caffeine Is Too Much?. Current as of 08/28/2024. Read 2026-10-23.
- Health Canada. Caffeine in foods. Page dated 2025-04-02. Read 2026-10-23.
- Chin JM, Merves ML, Goldberger BA, et al. Caffeine content of brewed teas. J Anal Toxicol. 2008. PMID 19007524. Read 2026-10-23.
- Ayakdaş G, Ağagündüz D. Determination of L-Theanine and Caffeine Contents in Tea Infusions with Different Fermentation Degrees and Brewing Conditions. Foods. 2025. PMID 40647065. Read 2026-10-23.
- Zhao Y, Asimi S, Wu K, et al. Black tea consumption and serum cholesterol concentration: systematic review and meta-analysis of randomized controlled trials. Clin Nutr. 2015. PMID 24972454. Read 2026-10-23.
- Mahdavi-Roshan M, Salari A, Ghorbani Z, Ashouri A. The effects of regular consumption of green or black tea beverage on blood pressure in those with elevated blood pressure or hypertension. Complement Ther Med. 2020. PMID 32507441. Read 2026-10-23.
- Igho-Osagie E, Cara K, Wang D, et al. Short-Term Tea Consumption Is Not Associated with a Reduction in Blood Lipids or Pressure. J Nutr. 2020. PMID 33188386. Read 2026-10-23.
- Kim Y, Je Y. Tea consumption and risk of all-cause, cardiovascular disease, and cancer mortality: a meta-analysis of thirty-eight prospective cohort data sets. Epidemiol Health. 2024. PMID 38938012. Read 2026-10-23.
- Jiang R, Chen J, Lin H, et al. The association between tea consumption and hypertension: a systematic review and meta-analysis. Front Nutr. 2026. PMID 42694065. Read 2026-10-23.
- Liu R, Li J, Liang Y. Tea consumption and cardiovascular risk and outcomes: mechanistic insights, epidemiological evidence, and clinical implications. Front Cardiovasc Med. 2026. PMID 42755895. Read 2026-10-23.
- Siener R, Hesse A. Effect of Black Tea Consumption on Urinary Risk Factors for Kidney Stone Formation. Nutrients. 2021. PMID 34959987. Read 2026-10-23.
- Haghighatdoost F, Sadeghian R, Abbasi B. The Associations Between Tea and Coffee Drinking and Risk of Calcium-Oxalate Renal Stones. Plant Foods Hum Nutr. 2021. PMID 34735676. Read 2026-10-23.
- Wu KH, Lee JI, Lee YC, et al. Habitual tea consumption is associated with a lower prevalence of kidney stone disease in postmenopausal women. PeerJ. 2024. PMID 39677960. Read 2026-10-23.
- Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. Br J Nutr. 1999. PMID 10999016. Read 2026-10-23.
- Mennen L, Hirvonen T, Arnault N, et al. Consumption of black, green and herbal tea and iron status in French adults. Eur J Clin Nutr. 2007. PMID 17299492. Read 2026-10-23.
- International Agency for Research on Cancer (IARC, WHO). IARC Monographs evaluate drinking coffee, maté, and very hot beverages (press release No. 244). 15 June 2016. Read 2026-10-23.
- Małyszek A, Zawiślak I, Kulus M, et al. Fluoride Content in Infusions of Selected Teas Available on the Polish Market. Foods. 2025. PMID 40724273. Read 2026-10-23.
- Małyszek A, Zawiślak I, Kulus M, et al. Assessment of Fluoride Intake Risk via Infusions of Commercial Leaf Teas Available in Poland. Foods. 2025. PMID 40941060. Read 2026-10-23.
- Hamitoğlu M, Şahin M, Esen G, et al. Assessment of the Potential Health Risks Associated with the Toxic and Essential Elements Content in Tea Samples Marketed in Türkiye. Turk J Pharm Sci. 2026. PMID 41960756. Read 2026-10-23.
- Payne ER, Aceves-Martins M, Dubost J, et al. Effects of Tea (Camellia sinensis) or its Bioactive Compounds l-Theanine or l-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants. Nutr Rev. 2025. PMID 40314930. Read 2026-10-23.