Peptides Explained

Basics: how peptides work in the body

In short

Reading the whole page takes about 2 minutes.

  • These pages explain how peptides work, step by step, in plain words.
  • They give no doses and do not tell you what to use.
  • Read them in order. Each page builds on the one before.
Last reviewed
A computer drawing of part of a protein on a black background: thin blue sticks for the chain and clouds of coloured dots around it.
A computer model of part of a protein. Scientists draw molecules like this to see their shape. Illustration: CSIRO, CSIRO ScienceImage (Wikimedia Commons) CC BY 3.0 Image details

Why read the basics first?

They explain why a peptide does what it does, and why so much is unknown.

A peptide is a short chain of amino acids, the same building blocks as the protein in your food. Your body uses many peptides as messages. Some medicines copy them.1,2,3

Four questions explain most of what this site says about any peptide:

Four questions explain most of what you need to know about a peptide.
QuestionWhy it mattersPage
What is it made of?Its size and shape decide where it can go and how long it lastsWhat is a peptide?
What does it switch on?One switch can act in many organs, and the body can push backHow signalling works
How long does it stay?This decides how long effects and side effects lastPharmacokinetics
Can it be swallowed?Your gut digests most peptides like foodWhy not a pill

Sources 4, 5, 6

The pages use examples from medicines that a regulator has checked, such as semaglutide. For those, a lot is known. For many peptides sold outside pharmacies, such as BPC-157, TB-500 and KPV, the same basic facts were never measured in people.7,8,9

These pages give no doses and no advice on what to use. If you already have a product, read product risk and the warning signs.

The basics pages

Where should I start?

Start with what a peptide is. Each page builds on the one before it.
  • What is a peptide?

    A peptide is a short chain of amino acids. How the chain is built, why its size matters, how chemists make it last, and why natural does not mean harmless.

  • How signalling works

    Peptides act by switching receptors on or off. How a signal is passed and multiplied inside a cell, why one molecule has many effects, and why precise is not harmless.

  • Pharmacokinetics

    What the body does to a peptide: absorption, spread, breakdown and removal. Why half-life drives everything, and why many unapproved peptides have no human data.

  • Why not a pill

    The gut treats a peptide like food protein. The physical reasons most peptides are injected, how the semaglutide tablet works around it, and what that costs.

Sources

Every claim on this page links to one of these sources. Scholarly sources link to their DOI; regulatory sources to the regulator's own page.

  1. National Human Genome Research Institute (NIH) (2026). Peptide — Talking Glossary of Genomic and Genetic Terms. Web page genome.gov — accessed 22 October 2026 ↩
  2. The Royal Swedish Academy of Sciences (1984). The Nobel Prize in Chemistry 1984: Press release. NobelPrize.org. Web page nobelprize.org — accessed 22 October 2026 ↩
  3. Muttenthaler M, King GF, Adams DJ, Alewood PF (2021). Trends in peptide drug discovery. Nature Reviews Drug Discovery 20:309-325. Review doi:10.1038/s41573-020-00135-8 ↩
  4. Di L (2015). Strategic approaches to optimizing peptide ADME properties. The AAPS Journal 17:134-143. Review doi:10.1208/s12248-014-9687-3 ↩
  5. Santiago M, Davis EA, Hinton T, Angelo TA, Shield A, Babey AM, et al. (2021). Defining and unpacking the core concepts of pharmacology education. Pharmacology Research & Perspectives 9:e00894. Research article doi:10.1002/prp2.894 ↩
  6. Zhu Q, Chen Z, Paul PK, Lu Y, Wu W, Qi J (2021). Oral delivery of proteins and peptides: Challenges, status quo and future perspectives. Acta Pharmaceutica Sinica B 11:2416-2448. Review doi:10.1016/j.apsb.2021.04.001 ↩
  7. U.S. Food and Drug Administration (2026). FDA Briefing Document for BPC-157-Related Bulk Drug Substances (BPC-157 (free base) and BPC-157 acetate), Pharmacy Compounding Advisory Committee meeting, 23–24 July 2026. Regulator fda.gov — accessed 20 October 2026 ↩
  8. U.S. Food and Drug Administration (2026). FDA Briefing Document for TB-500-Related Bulk Drug Substances (TB-500 (free base) and TB-500 acetate), Pharmacy Compounding Advisory Committee meeting, 23–24 July 2026. Regulator fda.gov — accessed 20 October 2026 ↩
  9. U.S. Food and Drug Administration (2026). FDA Briefing Document for KPV-Related Bulk Drug Substances (KPV (free base) and KPV acetate), Pharmacy Compounding Advisory Committee meeting, 23-24 July 2026. Regulator fda.gov — accessed 20 October 2026 ↩