Drug & supplement interaction

Black Tea + Cimetidine

Cimetidine brand names: Tagamet HB, Tagamet, Cimetidine Injection.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Cimetidine falls into 2 drug categories that Black Tea can interact with; the most serious is rated moderate. Theoretically, concomitant use might increase the levels and adverse effects of caffeine.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Black Tea and Cimetidine

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Black Tea interacts with whole categories of medication. Cimetidine falls into 2 of those categories, so it can interact with Black Tea in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 1A2 (CYP1A2) INHIBITORS

1 of 2

Why this applies to Cimetidine

Cimetidine falls under CYTOCHROME P450 1A2 (CYP1A2) INHIBITORS — the group Black Tea interacts with.

Theoretically, concomitant use might increase the levels and adverse effects of caffeine.
Black tea contains caffeine. Caffeine is metabolized by CYP1A2,. Theoretically, drugs that inhibit CYP1A2 may decrease the clearance rate of caffeine from black tea and increase caffeine levels.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thing with this pairing: it's really your morning tea that gets affected, not the cimetidine itself. Cimetidine slows down a liver enzyme called CYP1A2, and that's the same enzyme your body uses to clear out caffeine. So while you're taking cimetidine, the caffeine from black tea can hang around longer and build up a bit more than usual.

In plain terms, you might feel the effects of caffeine more strongly, think jitteriness, a racing or pounding heart, trouble sleeping, or feeling wired. This is theoretical, based on how the drugs work rather than strong studies, so for most folks a cup or two won't be a big deal. If you're caffeine-sensitive or notice those symptoms, ease up on the tea and chat with your pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Weisburger JH. Tea and health: the underlying mechanisms. Proc Soc Exp Biol Med 1999;220:271-5. PubMed
  2. Hagg S, Spigset O, Mjorndal T, Dahlqvist R. Effect of caffeine on clozapine pharmacokinetics in healthy volunteers. Br J Clin Pharmacol 2000;49:59-63. PubMed
  3. Carrillo JA, Benitez J. Clinically significant pharmacokinetic interactions between dietary caffeine and medications. Clin Pharmacokinet 2000;39:127-53. PubMed
  4. Kot, M. and Daniel, W. A. Effect of diethyldithiocarbamate (DDC) and ticlopidine on CYP1A2 activity and caffeine metabolism: an in vitro comparative study with human cDNA-expressed CYP1A2 and liver microsomes. Pharmacol Rep. 2009;61(6):1216-1220. PubMed
  5. Wojcikowski, J. and Daniel, W. A. Perazine at therapeutic drug concentrations inhibits human cytochrome P450 isoenzyme 1A2 (CYP1A2) and caffeine metabolism--an in vitro study. Pharmacol Rep. 2009;61(5):851-858. PubMed
  6. Wang, X. and Yeung, J. H. Effects of the aqueous extract from Salvia miltiorrhiza Bunge on caffeine pharmacokinetics and liver microsomal CYP1A2 activity in humans and rats. J Pharm Pharmacol 2010;62(8):1077-1083.
  7. Kot M, Daniel WA. Caffeine as a marker substrate for testing cytochrome P450 activity in human and rat. Pharmacol Rep 2008;60:789-97.
  8. Kjaerstad MB, Nielsen F, Nohr-Jensen L, et al. Systemic uptake of miconazole during vaginal suppository use and effect on CYP1A2 and CYP3A4 associated enzyme activities in women. Eur J Clin Pharmacol 2010;66:1189-97. PubMed
  9. Goh BC, Reddy NJ, Dandamudi UB, et al. An evaluation of the drug interaction potential of pazopanib, an oral vascular endothelial growth factor receptor tyrosine kinase inhibitor, using a modified Cooperstown 5+1 cocktail in patients with advanced solid t
  10. Chen Y, Kang Z, Yan J, et al. Liu wei di huang wan, a well-known traditional Chinese medicine induces CYP1A2 while suppressing CYP2A6 and N-acetyltransferase 2 acivities in man. J Ethnopharmacol 2010;132:213-8.
  11. Suzuki S, Murayama Y, Sugiyama E, et al. Estimating pediatric doses of drugs metabolized by cytochrome P450 (CYP) isozymes, based on physiological liver development and serum protein levels. Yakugaku Zasshi 2010;130:613-20. PubMed
  12. Chien CF, Wu YT, Lee WC, et al. Herb-drug interaction of Andrographis paniculata extract and andrographolide on the pharmacokinetics of theophylline in rats. Chem Biol Interact 2010;184:458-65. PubMed
  13. Mills BM, Zaya MJ, Walters RR, et al. Current cytochrome P450 phenotyping methods applied to metabolic drug -drug interaction prediction in dogs. Drug Metab Dispos 2010;38:396-404. PubMed
  14. Turpault S, Brian W, Van Horn R, et al. Pharmacokinetic assessment of a five-probe cocktail for CYPs 1A2, 2C9, 2C19, 2D6, and 3A. Br J Clin Pharmacol 2009;68:928-35. PubMed
  15. Filimonova AA, Ziganshina LE, Ziganshin AU, Chichirov AA. On the possibility of patient phenotyping on the basis of cytochrome p-450 1A2 isoenzyme activity using caffeine as the test substrate. Eksp Klin Farmakol 2009;72:61-5.
  16. Jenkins J, Williams D, Deng Y, et al. Eltrombopag, an oral thrombopoietin receptor agonist, has no impact on the pharmacokinetic profile of probe drugs for cytochrome P450 isoenzymes CYP3A4, CYP1A2, CYP2C9 and CYP2C19 in healthy men: a cocktail analysis.
  17. Perera, V., Gross, A. S., and McLachlan, A. J. Caffeine and paraxanthine HPLC assay for CYP1A2 phenotype assessment using saliva and plasma. Biomed.Chromatogr. 2010;24(10):1136-1144. PubMed
  18. Izzo, A. A. and Ernst, E. Interactions between herbal medicines and prescribed drugs: an updated systematic review. Drugs 2009;69(13):1777-1798. PubMed
Moderate

CIMETIDINE (Tagamet)

2 of 2
Theoretically, concomitant use might increase the effects and adverse effects of caffeine in black tea.
Black tea contains caffeine. Cimetidine can reduces caffeine clearance by 31% to 42%.
Severity Moderate Likelihood Likely Evidence B

Well-controlled human studies have demonstrated the likely existence of this interaction.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here the roles are flipped from what people usually expect. Cimetidine is the one doing the blocking. It slows down the liver enzymes that normally clear caffeine, so the caffeine from your black tea hangs around longer. Studies suggest cimetidine can cut caffeine clearance by roughly 31% to 42%, which means a cup of tea may hit you harder and stay with you longer than usual.

In real life, that can look like feeling jittery, a faster or fluttery heartbeat, trouble sleeping, or a bit of stomach upset. It does not make the cimetidine itself dangerous, and ordinary tea drinking is fine for most folks. If you notice these effects, simply cutting back on caffeine often helps. Check with your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. May DC, Jarboe CH, VanBakel AB, Williams WM. Effects of cimetidine on caffeine disposition in smokers and nonsmokers. Clin Pharmacol Ther 1982;31:656-61. PubMed
  2. Broughton LJ, Rogers HJ. Decreased systemic clearance of caffeine due to cimetidine. Br J Clin Pharmacol 1981;12:155-9. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Black Tea Also Interacts With Other Medications

Black Tea has 8 major, 571 moderate, 114 minor known drug interactions in our database — the Cimetidine one above is among them. If you take anything else, check it against the full list below.

Major 8 Moderate 571 Minor 114 No known interaction 2,137 (incl. Cimetidine)
Taking anything else?

Check Another of Your Medications Against Black Tea

Covers the 2,830 medications we’ve checked against Black Tea. Pick one to open its full report.

From our Q&A

Questions About Black Tea or Cimetidine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Black Tea or Cimetidine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Cimetidine

This page covers Black Tea only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cimetidine page lists 95 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Pu-erh Tea (major), St. John's Wort (major), Adrafinil (moderate) and African Wild Potato (moderate).

By severity: 3 major · 63 moderate · 29 minor.

Open the Cimetidine interaction page

One more smart check

Taking Black Tea as Part of a Dietary Supplement Product? Check It for Interactions

We hold 271 real supplement products containing Black Tea, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Black Tea. Your product may carry other ingredients that interact with Cimetidine too, on top of Black Tea — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Black Tea and Cimetidine Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Black Tea
Top 25%

#280 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Cimetidine
Steady interest

#1,832 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Black Tea

What is Black Tea?

  • Mental alertness and energy
  • Heart health support
  • Blood pressure and cholesterol
  • Digestive complaints
  • Weight management
  • Antioxidant support

Black tea is a popular caffeinated drink made from the fully oxidized leaves of the Camellia sinensis plant, and it contains caffeine and antioxidant plant compounds. Moderate tea drinking is generally safe for most adults and may modestly support heart health and alertness, but it is not a proven treatment for any disease. If you are pregnant, breastfeeding, sensitive to caffeine, or taking medicines, talk to your pharmacist or doctor.

Read the full Black Tea monograph & all interactions
Medication

About Cimetidine

What Is Cimetidine Used For?

Brand names: Tagamet HB, Tagamet, Cimetidine Injection

Cimetidine tablets sold over the counter — including brands like Acid Controller, Acid Reducer, Basic Care Acid Reducer, Equate Cimetidine, and cimetidine 200 — are used to relieve heartburn associated with acid indigestion and sour stomach, and to prevent heartburn brought on by eating or drinking certain foods and beverages.

Prescription-strength cimetidine tablets and Cimetidine Hydrochloride Oral Solution are used for more serious conditions: short-term treatment of active duodenal ulcers (ulcers in the upper small intestine) and benign gastric ulcers (stomach ulcers), maintenance therapy to keep duodenal ulcers from coming back, healing of erosive GERD (acid reflux that has damaged the lining of the esophagus), and treatment of conditions that cause the stomach to make too much acid — such as Zollinger-Ellison Syndrome, systemic mastocytosis, and multiple endocrine adenomas.

See full Cimetidine drug information
Keep checking

Other Drugs & Black Tea

Browse every other medication we’ve checked against Black Tea — both the ones with a known interaction and the ones without. Select any drug for the full detail.

8Major
571Moderate
114Minor
2,136No known interaction
8 Major 571 Moderate 114 Minor 2,136 No interaction
Major

8 interactions

Moderate

571 interactions

Showing 60 of 571 moderate interactions — see all 571 on the Black Tea page.

Minor

114 interactions

Showing 60 of 114 minor interactions — see all 114 on the Black Tea page.

No interaction 2,136 drugs checked — show the list

We also checked Black Tea against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,136 medications checked with no known interaction — see the full Black Tea list.

See the full Black Tea interactions page
See every supplement checked against Cimetidine, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Black Tea monograph › Uses, safety, and every drug interaction in one place Cimetidine supplement interactions › Every supplement checked against Cimetidine, ranked by severity Cimetidine drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Black Tea and Cimetidine Together: Common Questions

Can you take Black Tea with Cimetidine?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Black Tea and Cimetidine?
Cimetidine belongs to more than one drug category, and Black Tea interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Black Tea and Cimetidine interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Cimetidine and Black Tea?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.