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New to Peptides · Part 2: The best-known peptides today

GHK-Cu (copper peptide)

Lesson 12.2.6 · 4 min read · Free lesson

Where it stands: early human data, mainly in skin care (yellow).

GHK-Cu is a tiny peptide of just three amino acids attached to copper. It occurs naturally in human blood, and levels fall with age 16. You'll find it in many face creams and serums.

How strong is the evidence?

For skin, there are several small studies, usually 12 weeks long, that report firmer skin and fewer fine lines 16. Many were run or paid for by companies, and some were never fully published 16. Lab studies show it can help build collagen, the protein that keeps skin firm 16.

Shots are a different story

Injecting GHK-Cu is popular online, but there's almost no human research on it. The FDA has raised concerns about immune reactions and impurities in injectable peptides like this one 11.

The honest takeaway

Using a cream is low-risk with modest benefits. Injecting it is a guess.

Check what you learned: take this lesson's quick quiz in the Academy. It is free.

Sources

  1. DailyMed - WEGOVY (semaglutide) injection and tablets, prescribing information (revised 6/2026)
  2. Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med 2021
  3. Lincoff AM et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT). N Engl J Med 2023
  4. FDA approval letter - Wegovy (semaglutide) tablets, NDA 218316 (Dec 22, 2025)
  5. FDA label - ZEPBOUND (tirzepatide) injection, revised 04/2026
  6. Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med 2022;387(3):205-216
  7. Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial. N Engl J Med 2023
  8. AJMC - Retatrutide achieves up to 30.3% average weight loss in phase 3 TRIUMPH-1 trial (May 2026)
  9. Józwiak M, Bauer M, Kamysz W, Kleczkowska P. Multifunctionality and Possible Medical Application of the BPC 157 Peptide - Literature and Patent Review. Pharmaceuticals 2025;18(2):185
  10. Lee E, Padgett B. Intra-articular injection of BPC 157 for multiple types of knee pain. Altern Ther Health Med 2021;27(4):8-13 (PMID 34324435)
  11. FDA - Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (content current as of 04/22/2026)
  12. HHS - Enforcement Discretion Policy Regarding 503A Compounding Using Certain Peptide Bulk Drug Substances (policy text with appendices, October 2026)
  13. World Anti-Doping Agency - Prohibited List 2026
  14. Goldstein AL, Hannappel E, Sosne G, Kleinman HK. Thymosin beta4: a multi-functional regenerative peptide. Expert Opin Biol Ther 2012 (PMID 22074294)
  15. Sosne G, Kleinman HK, Springs C, et al. 0.1% RGN-259 (thymosin beta 4) ophthalmic solution in neurotrophic keratopathy (SEER-1). Int J Mol Sci 2023;24(1):554
  16. Pickart L, Margolina A. Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data. Int J Mol Sci 2018;19(7):1987
  17. Teichman SL et al. Prolonged stimulation of GH and IGF-I secretion by CJC-1295, a long-acting analog of GHRH, in healthy adults. J Clin Endocrinol Metab 2006
  18. FDA briefing document, Pharmacy Compounding Advisory Committee, Dec 4, 2024: CJC-1295-related bulk drug substances
  19. Beck DE et al. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for postoperative ileus in bowel cancer resection patients. Int J Colorectal Dis 2014
  20. FDA briefing document, Pharmacy Compounding Advisory Committee, Oct 29, 2024: ipamorelin and ipamorelin acetate
  21. Vyleesi (bremelanotide injection) Prescribing Information - FDALabel
  22. Healio - FDA approves Vyleesi for women with low sexual desire (June 21, 2019)
  23. FDA label - RYBELSUS (semaglutide) tablets, 2026

← TB-500 (thymosin beta-4) · All lessons in New to Peptides · CJC-1295 and ipamorelin →