Drug & supplement interaction

Psilocybin + Phentermine

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

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

Psilocybin has a moderate interaction with Phentermine. Theoretically, concomitant use of psilocybin with stimulant drugs might increase stimulant adverse effects.

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

Psilocybin and Phentermine

Here is the interaction we found between these two, with the evidence behind it.

Moderate

STIMULANT DRUGS

Why this applies to Phentermine

Phentermine falls under STIMULANT DRUGS — the group Psilocybin interacts with.

Theoretically, concomitant use of psilocybin with stimulant drugs might increase stimulant adverse effects.
Due to the central nervous system (CNS) stimulant effects of psilocybin, concomitant use with stimulant drugs may increase the risk of adverse effects.
Severity Moderate Likelihood Probable Evidence D

Interaction 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..

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

Here's the simple version: phentermine is a stimulant that revs up your nervous system, and psilocybin (the active part of certain mushrooms) also stirs up the brain through serotonin pathways. Stacking two activating substances can add together, so the worry is more of phentermine's usual stimulant side effects, things like a racing or pounding heart, higher blood pressure, jitteriness, trouble sleeping, and feeling anxious or wired.

I want to be honest that this is a theoretical caution based on how each one works, not on solid studies of the two together. Keep in mind psilocybin is investigational and illegal in most places, and the mental effects alone are unpredictable. Please don't change anything on your own, just talk it over with your doctor or pharmacist first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Griffiths RR, Johnson MW, Carducci MA, et al. Psilocybin produces substantial and sustained decreases in depression and anxiety in patients with life-threatening cancer: A randomized double-blind trial. J Psychopharmacol 2016;30(12):1181-1197. PubMed
  2. Bogenschutz MP, Forcehimes AA, Pommy JA, Wilcox CE, Barbosa PC, Strassman RJ. Psilocybin-assisted treatment for alcohol dependence: a proof-of-concept study. J Psychopharmacol 2015;29(3):289-99. PubMed
  3. Grob CS, Danforth AL, Chopra GS, et al. Pilot study of psilocybin treatment for anxiety in patients with advanced-stage cancer. Arch Gen Psychiatry 2011;68(1):71-8. PubMed
  4. Brown RT, Nicholas CR, Cozzi NV, et al. Pharmacokinetics of Escalating Doses of Oral Psilocybin in Healthy Adults. Clin Pharmacokinet 2017;56(12):1543-1554. PubMed
  5. Carbonaro TM, Bradstreet MP, Barrett FS, et al. Survey study of challenging experiences after ingesting psilocybin mushrooms: Acute and enduring positive and negative consequences. J Psychopharmacol 2016;30(12):1268-1278. PubMed
  6. Hasler F, Grimberg U, Benz MA, Huber T, Vollenweider FX. Acute psychological and physiological effects of psilocybin in healthy humans: a double-blind, placebo-controlled dose-effect study. Psychopharmacology (Berl) 2004;172(2):145-56. PubMed
  7. Bienemann B, Ruschel NS, Campos ML, Negreiros MA, Mograbi DC. Self-reported negative outcomes of psilocybin users: A quantitative textual analysis. PLoS One 2020;15(2):e0229067. PubMed
  8. Carbonaro TM, Johnson MW, Griffiths RR. Subjective features of the psilocybin experience that may account for its self-administration by humans: a double-blind comparison of psilocybin and dextromethorphan. Psychopharmacology (Berl) 2020;237(8):2293-2304. PubMed
  9. Anderson BT, Danforth A, Daroff PR, et al. Psilocybin-assisted group therapy for demoralized older long-term AIDS survivor men: An open-label safety and feasibility pilot study. EClinicalMedicine 2020;27:100538. PubMed
  10. Carbonaro TM, Johnson MW, Hurwitz E, Griffiths RR. Double-blind comparison of the two hallucinogens psilocybin and dextromethorphan: similarities and differences in subjective experiences. Psychopharmacology (Berl) 2018;235(2):521-534. PubMed
  11. Bravermanová A, Viktorinová M, Tyl š F, et al. Psilocybin disrupts sensory and higher order cognitive processing but not pre-attentive cognitive processing-study on P300 and mismatch negativity in healthy volunteers. Psychopharmacology (Berl) 201 PubMed
  12. Wackermann J, Wittmann M, Hasler F, Vollenweider FX. Effects of varied doses of psilocybin on time interval reproduction in human subjects. Neurosci Lett 2008;435(1):51-5. PubMed
  13. Fadiman J, Korb S. Might Microdosing Psychedelics Be Safe and Beneficial? An Initial Exploration. J Psychoactive Drugs 2019;51(2):118-122. 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

Psilocybin Also Interacts With Other Medications

Psilocybin has 292 moderate known drug interactions in our database — the Phentermine one above is one of them. If you take anything else, check it against the full list below.

Moderate 292 No known interaction 2,538 (incl. Phentermine)
Taking anything else?

Check Another of Your Medications Against Psilocybin

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

From our Q&A

Questions About Psilocybin 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 Psilocybin 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 Psilocybin 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

How much people look this up

Where Psilocybin 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 Psilocybin
Top half

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

29 days ago today
Medication Phentermine
Top half

#1,098 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 Psilocybin

What is Psilocybin?

  • Depression
  • Anxiety (including in serious illness)
  • Substance use disorders
  • Post-traumatic stress
  • Spiritual or psychological exploration

Psilocybin is a powerful psychedelic compound found in certain mushrooms and is being studied for hard-to-treat depression, anxiety, and addiction, but it is still investigational and not an approved supplement. It is illegal in most places, can cause intense and unpredictable mental effects, and should never be used outside of a supervised clinical setting.

Read the full Psilocybin 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 used as a short-term add-on (a few weeks) to a weight-loss plan built on exercise, behavior changes and fewer calories. It is for managing exogenous obesity (obesity not caused by another medical condition).

It is meant for people with a starting body mass index (BMI) of 30 or higher. It can also be used at a BMI of 27 or higher when other risk factors are present, such as controlled high blood pressure, diabetes or high cholesterol or other blood fats (hyperlipidemia).

See full Phentermine drug information
Keep checking

Other Drugs & Psilocybin

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

0Major
292Moderate
0Minor
2,537No known interaction
292 Moderate 2,537 No interaction
Moderate

292 interactions

Showing 60 of 292 moderate interactions — see all 292 on the Psilocybin page.

No interaction 2,537 drugs checked — show the list

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

Showing the 60 most looked-up of 2,537 medications checked with no known interaction — see the full Psilocybin list.

See the full Psilocybin interactions page
See every supplement checked against Phentermine, 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
Psilocybin monograph › Uses, safety, and every drug interaction in one place Phentermine supplement interactions › Every supplement checked against Phentermine, ranked by severity Phentermine 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 Psilocybin and Phentermine Together: Common Questions

Can you take Psilocybin with Phentermine?
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.
How serious is the Psilocybin and Phentermine 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 Phentermine and Psilocybin?

Our pharmacists answer your medication & supplement questions — free.

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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.