Drug & supplement interaction

Black Pepper + Phentermine

Phentermine brand names: Adipex-P, Fastin, T Diet, Phentride, Obenix, and others.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Black Pepper and Phentermine in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Black Pepper and Phentermine

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Phentermine and Black Pepper in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Black Pepper safety at a glance

Black Pepper overall Generally safe Generally safe as a food spice; concentrated supplements should be used more cautiously.
Pregnancy Likely Safe When used orally in amounts commonly found in foods. Read the full pregnancy detail
Breastfeeding Likely Safe When used orally in amounts commonly found in foods. There is insufficient reliable information available about the safety of black pepper when used in medicina... Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Phentermine and Black Pepper? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Phentermine

Interactions in our licensed database are recorded against drug classes, not just single drug names. Phentermine is filed under 2 classifications — stimulant drugs, oral drugs. Black Pepper has documented interactions with 17 drug classes — the most serious being anticoagulant/antiplatelet drugs (moderate), antidiabetes drugs (moderate) and atorvastatin (lipitor) (moderate) — and none of Phentermine’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Black Pepper Does Interact With Other Medications

Black Pepper has 976 moderate, 43 minor known drug interactions in our database — Phentermine isn’t one of them. If you take anything else, check it against the full list below.

Moderate 976 Minor 43 No known interaction 1,811 (incl. Phentermine)
Taking anything else?

Check Another of Your Medications Against Black Pepper

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

What to actually watch for

No Interaction Found — But Data Suggests Black Pepper and Phentermine May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do. One of them is worth acting on rather than waiting out — marked below.

  • Hives Worth acting on Additional detail

    Black Pepper

    “In one case report, a 17-month-old male developed hives, red eyes, facial swelling, and a severe cough following consumption of a sauce containing multiple ingredients. Allergen skin tests were positive to both black pepper and cayenne, which were found in the sauce.”

    Black Pepper · Natural Medicines adverse-effect record, reported in cough.

    1 source cited
    1. 93947. Gimenez L, Zacharisen M. Severe pepper allergy in a young child. WMJ. 2011 Jun;110(3):138-9.

    Phentermine

    Listed in the ADVERSE REACTIONS section of the FDA label for Phentermine. Read the label on DailyMed ›

  • Stomach upset Additional detail

    Black Pepper

    “Orally, black pepper can cause a burning aftertaste and dyspepsia. Single and repeated application of piperine, the active constituent in black pepper, to the tongue and oral cavity can decrease taste perception. By intragastric route, black pepper 1.5 grams has been reported to cause gastrointestinal microbleeds. It is not clear if such an effect would occur with oral administration.”

    Black Pepper · Natural Medicines adverse-effect record, reported in dyspepsia.

    4 sources cited
    1. 5619. Cohle SD, Trestrail JD III, Graham MA, et al. Fatal pepper aspiration. Am J Dis Child 1988;142:633-6. PubMed
    2. 38061. Marotta, R. B. and Floch, M. H. Diet and nutrition in ulcer disease. Med Clin North Am 1991;75(4):967-979. PubMed
    3. 29267. Lawless, H. and Stevens, D. A. Effects of oral chemical irritation on taste. Physiol Behav. 1984;32(6):995-998. PubMed
    4. 29164. Myers, B. M., Smith, J. L., and Graham, D. Y. Effect of red pepper and black pepper on the stomach. Am J Gastroenterol 1987;82(3):211-214.

    Phentermine

    Listed in the ADVERSE REACTIONS section of the FDA label for Phentermine. Read the label on DailyMed ›

Reported for Black Pepper but not commonly for Phentermine: an allergic reaction, a change in taste, swelling and eye irritation or redness.

Effects for Phentermine come from the ADVERSE REACTIONS section of its FDA label; effects for Black Pepper come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Black Pepper in Pregnancy & Breastfeeding

Pregnancy Likely Safe

When used orally in amounts commonly found in foods.

Pregnancy Likely Unsafe

When used orally in large amounts. Black pepper might have abortifacient effects; contraindicated. There is insufficient reliable information available about the safety of topical pepper when used during pregnancy.

Lactation Likely Safe

When used orally in amounts commonly found in foods. There is insufficient reliable information available about the safety of black pepper when used in medicinal amounts during breast-feeding.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

Overlapping uses

What Phentermine Is Prescribed For, and What Black Pepper Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Phentermine is a prescription medicine with approved uses on its FDA label. Black Pepper is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Phentermine is prescribed for: Phentermine is approved as a short-term addition to a weight-loss program — not a standalone treatment. It is used alongside reduced-calorie eating, increased physical activity, and behavior changes to help manage obesity in adults whose body mass index (BMI) is 30 kg/m² or higher, or 27 kg/m² or higher when other risk factors such as controlled high blood pressure, diabetes, or high cholesterol (hyperlipidemia) are also present. All available phentermine products — including Adipex-P, Lomaira, and various generic capsules and tablets — share this same FDA-approved use. Lomaira tablets are specifically dosed to be taken three times daily before meals, while other formulations are generally taken once daily.

Read the rest of what Phentermine is prescribed for

Treatment is intended to last only a few weeks.

Black Pepper has been studied for:

  • Obesity studied, not established Black Pepper has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Black Pepper for obesity

    Although there has been interest in using oral black pepper for obesity, there is insufficient reliable information about the clinical effects of black pepper for this purpose.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Phentermine on your own; if you are taking Black Pepper for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Black Pepper or Phentermine

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 Pepper or Phentermine, 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 Phentermine

This page covers Black Pepper only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phentermine page lists 61 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Ephedra (major), Peyote (major), Rauvolfia Vomitoria (major) and Sida Cordifolia (major).

By severity: 5 major · 43 moderate · 13 minor.

From our pharmacist’s overview on the Phentermine page

“Ephedra is the pairing I most want anyone taking phentermine (Adipex-P) to know about. Phentermine is itself a stimulant appetite suppressant that raises heart rate and blood pressure, and ephedra piles the same cardiovascular strain on top of it.”

Reviewed by 2 · Jul 18, 2026

Open the Phentermine interaction page

One more smart check

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

We hold 5,528 real supplement products containing Black Pepper, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Black Pepper. Even though Black Pepper itself has no known interaction with Phentermine, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Black Pepper and Phentermine 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 Pepper
Top 5%

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

29 days ago today
Medication Phentermine
Top 25%

#576 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Black Pepper reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Black Pepper and Phentermine records this page draws on were last updated July 11, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Black Pepper

What is Black Pepper?

Black Pepper
  • Flavoring and culinary use
  • Digestive complaints like bloating and indigestion
  • Boosting absorption of other supplements
  • Antioxidant and anti-inflammatory support
  • Cold and congestion remedies

Black pepper is a common kitchen spice that is generally safe in the amounts used in food. Its extract, piperine, is mostly added to supplements to help the body absorb other ingredients (like curcumin from turmeric). Strong human evidence for black pepper treating specific health conditions is limited, so use supplement-strength products with care and check with your pharmacist.

Piper nigrum · Piperaceae · Dried fruit (peppercorn) and its extract piperine · Whole or ground spice, capsules, standardized piperine extracts (often labeled BioPerine), essential oil

An interaction check asks whether these two react with each other — it does not ask whether Black Pepper is a good idea for someone in your situation. Here is what our Black Pepper record says about it on its own.

Black Pepper: dosing

There is no official standardized dose of black pepper or piperine for any health condition. In supplements, piperine is often included in small amounts mainly to improve absorption of other ingredients.If you choose a black pepper or piperine product, follow the directions on the label and do not exceed the suggested amount.

From our Black Pepper monograph — the full record covers uses, side effects and every documented interaction.

Read the full Black Pepper monograph & all interactions
Medication

About Phentermine

What Is Phentermine Used For?

Brand names: Adipex-P, Fastin, T Diet, Phentride, Obenix, Pbc Phentride, Pbw Phentride, Phentrol #3, Ionamin, Phentrol #6, Phentrol #2, Phentrol #5, Phentrol, Obermine, Phentermine, Suprenza

Phentermine is approved as a short-term addition to a weight-loss program — not a standalone treatment. It is used alongside reduced-calorie eating, increased physical activity, and behavior changes to help manage obesity in adults whose body mass index (BMI) is 30 kg/m² or higher, or 27 kg/m² or higher when other risk factors such as controlled high blood pressure, diabetes, or high cholesterol (hyperlipidemia) are also present.

All available phentermine products — including Adipex-P, Lomaira, and various generic capsules and tablets — share this same FDA-approved use. Lomaira tablets are specifically dosed to be taken three times daily before meals, while other formulations are generally taken once daily. Treatment is intended to last only a few weeks.

See full Phentermine drug information
Keep checking

Other Drugs & Black Pepper

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

0Major
976Moderate
43Minor
1,810No known interaction
976 Moderate 43 Minor 1,810 No interaction
Moderate

976 interactions

Showing 60 of 976 moderate interactions — see all 976 on the Black Pepper page.

Minor

43 interactions

No interaction 1,810 drugs checked — show the list

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

Showing the 60 most looked-up of 1,810 medications checked with no known interaction — see the full Black Pepper list.

See the full Black Pepper interactions page
See every supplement checked against Phentermine, ranked by severity
Evidence & sources

Black Pepper References

The 29 references that drive our Black Pepper monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  3. Bano G, Amla V, Raina RK, et al. The effect of piperine on pharmacokinetics of phenytoin in healthy volunteers. Planta Med 1987;53:568-9. PubMed
  4. Bano G, et al. Effect of piperine on bioavailability and pharmacokinetics of propranolol and theophylline in healthy volunteers. Eur J Clin Pharmacol 1991;41;615-7. PubMed
  5. Cohle SD, Trestrail JD III, Graham MA, et al. Fatal pepper aspiration. Am J Dis Child 1988;142:633-6. PubMed
  6. Bhardwaj RK, Glaeser H, Becquemont L, et al. Piperine, a major constituent of black pepper, inhibits human P-glycoprotein and CYP3A4. J Pharmacol Exp Ther 2002;302:645-50. PubMed
  7. Velpandian T, Jasuja R, Bhardwaj RK, et al. Piperine in food: interference in the pharmacokinetics of phenytoin. Eur J Drug Metab Pharmacokinet 2001;26:241-7. PubMed
  8. Pattanaik S, Hota D, Prabhakar S, et al. Pharmacokinetic interaction of a single dose of piperine with steady-state carbamazepine in epilepsy patients. Phytother Res 2009;23:1281-6.
  9. Munakata, M., Kobayashi, K., Niisato-Nezu, J., Tanaka, S., Kakisaka, Y., Ebihara, T., Ebihara, S., Haginoya, K., Tsuchiya, S., and Onuma, A. Olfactory stimulation using black pepper oil facilitates oral feeding in pediatric patients receiving long-term en
  10. Myers, B. M., Smith, J. L., and Graham, D. Y. Effect of red pepper and black pepper on the stomach. Am J Gastroenterol 1987;82(3):211-214.
  11. Raghavendra, R. H. and Naidu, K. A. Spice active principles as the inhibitors of human platelet aggregation and thromboxane biosynthesis. Prostaglandins Leukot.Essent.Fatty Acids 2009;81(1):73-78. PubMed
  12. Subehan, Usia, T., Kadota, S., and Tezuka, Y. Mechanism-based inhibition of human liver microsomal cytochrome P450 2D6 (CYP2D6) by alkamides of Piper nigrum. Planta Med 2006;72(6):527-532.
  13. Kasibhatta, R. and Naidu, M. U. Influence of piperine on the pharmacokinetics of nevirapine under fasting conditions: a randomised, crossover, placebo-controlled study. Drugs R.D. 2007;8(6):383-391. PubMed
  14. Usia, T., Iwata, H., Hiratsuka, A., Watabe, T., Kadota, S., and Tezuka, Y. CYP3A4 and CYP2D6 inhibitory activities of Indonesian medicinal plants. Phytomedicine. 2006;13(1-2):67-73. PubMed
  15. Mujumdar, A. M., Dhuley, J. N., Deshmukh, V. K., Raman, P. H., Thorat, S. L., and Naik, S. R. Effect of piperine on pentobarbitone induced hypnosis in rats. Indian J Exp.Biol. 1990;28(5):486-487.

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Black Pepper and Phentermine Together: Common Questions

Is it safe to take Black Pepper with Phentermine?
We do not list a known interaction between Black Pepper and Phentermine. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Black Pepper and Phentermine have any of the same side effects?
Yes — our sources link each of them separately to 2 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Are Black Pepper and Phentermine used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Black Pepper in each. That is a conversation for your prescriber, especially if Phentermine is being adjusted to a target.
How was the Black Pepper and Phentermine combination checked?
Interactions in our licensed database are recorded against drug classes. Phentermine is filed under 2 classifications, and Black Pepper has documented interactions with 17 drug classes — none of Phentermine's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Black Pepper interact with any other medications?
Yes. Black Pepper has 1,019 documented drug interactions in our database — Phentermine is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Phentermine interact with any supplements?
Yes. Phentermine has documented interactions with 61 supplements in our database — Black Pepper is not one of them. The Phentermine interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Black Pepper monograph Uses, safety profile, and every drug interaction in one place Phentermine drug information The full plain-English guide to this medication Phentermine supplement interactions Every supplement checked against Phentermine, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 29 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Phentermine and Black Pepper?

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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.