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Weight-loss and diabetes medicines (GLP-1)

This card sets out what was located on whether GLP-1 medicines change the effect of a classic psychedelic, and what was not.

Published Information current to 7 November 2026Review due by 5 February 2027

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The short answer

Do GLP-1 medicines change the effect of a classic psychedelic?

The question here is whether GLP-1 medicines (semaglutide, tirzepatide, liraglutide) change the effect of a classic psychedelic. As far as a documented search found, no one has tested it. Searches on 7 November 2026 of PubMed, Europe PMC (including preprints) and ClinicalTrials.gov located no study, in people or animals, of whether a GLP-1 medicine changes the experience of a classic psychedelic or how the body handles it, and no registered study. This card does not say whether these medicines dull the effect or leave it unchanged. It does not address starting, continuing or stopping any medicine. That belongs with the person who prescribes it.

What was found?

Related work asks different questions. These medicines are approved for type 2 diabetes and obesity, so findings about them describe those groups, not healthy adults.

  • Serotonin in animals. In rats, depleting brain serotonin weakened the weight loss caused by a GLP-1 agonist, and blocking the 5-HT2A receptor in the brain did the same. The authors call the data preclinical and preliminary. Source 1, level 1
  • A mouse laboratory found otherwise. Blocking serotonin production did not change liraglutide's effect, and a 5-HT2A agonist given 14 or 24 hours earlier blunted its short-term effect on eating. The authors note the conflict with the rat study, possibly a species difference. Source 2, level 1
  • Psilocybin and liraglutide in mice. A single dose of psilocybin did not add to liraglutide's weight loss. The question was whether psilocybin adds to weight loss, not whether the medicine changes the psilocybin experience, which a mouse study cannot report. Source 3, level 1
  • Stomach emptying. GLP-1 medicines slow it. A 2025 pharmacology review summarises studies in which other oral medicines were given alongside them and reports that most of the medicines studied showed no clinically significant interaction related to delayed emptying. No psychedelic was among the medicines tested. Source 4, level 1

What is not known?

“Not located” means that the searches Metanoia ran on 7 November 2026 did not return it. They covered PubMed, Europe PMC including preprints and ClinicalTrials.gov. Google Scholar, PsyArXiv, OSF, keyword search of bioRxiv and medRxiv, prescribing information and trial protocols were not searched. More searching could change the picture.

  • Whether a GLP-1 medicine changes the subjective effects of any classic psychedelic in people. Not located.
  • Whether slower stomach emptying changes how an oral psychedelic is absorbed. Not located.
  • Whether the animal findings carry over to people. Not known, and the two rodent results conflict.

What this card does not say

  • It does not say these medicines dull a psychedelic effect or leave it unchanged, or that combining them is safe or unsafe.
  • It does not say what anyone should do about a medicine. It is not a standard of care and not medical advice.
  • It does not rate how risky, safe or worthwhile any practice is.

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Where does this come from?

Grade key: 1 = peer-reviewed publication or official document. A grade names the type of source, and the design and limits are given in the text. “Full text read” means Metanoia read the body of the paper in full on the date given, and any part not read is named. Papers found and not read in full carry no claim.

Review due by 5 February 2027.

  1. Anderberg RH et al. Glucagon-like peptide 1 and its analogs act in the dorsal raphe and modulate central serotonin to reduce appetite and body weight. Diabetes 2017. PMC6237271 PMID 28057699. Grade 1. Rat study. Full text read 7 November 2026 (figures not read).
  2. Nonogaki K et al. Liraglutide, a GLP-1 receptor agonist, which decreases hypothalamic 5-HT2A receptor expression, reduces appetite and body weight independently of serotonin synthesis in mice. J Diabetes Res 2018. PMC5816835 PMID 29484303. Grade 1. Mouse study. Full text read 7 November 2026 (figures not read).
  3. Fadahunsi N et al. Acute and long-term effects of psilocybin on energy balance and feeding behavior in mice. Transl Psychiatry 2022. PMC9372155 PMID 35953488. Grade 1. Mouse study. Full text read 7 November 2026 (figures and supplement not read).
  4. Min JS et al. A comprehensive review on the pharmacokinetics and drug-drug interactions of approved GLP-1 receptor agonists and a dual GLP-1/GIP receptor agonist. Drug Des Devel Ther 2025. PMC12052016 PMID 40330819. Grade 1. Peer-reviewed review, secondary to the regulatory documents it summarises. Full text read 7 November 2026 (figures not read).