Pinc PeptideThe girly peptide research blog

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What are peptides? The science in plain English

How amino acids join into peptides, where a peptide ends and a protein begins, which peptides the body makes, and why most peptide drugs are injected. Every word is on screen.

Read the guide The video as text

From Google search · 30 September 2026 · 8 October 2026

People also ask about peptides 146 questions from 157 shown on 40 searches, 121 linked to a sourced answer

Google shows a “People also ask” box of related questions on many searches. We ran 24 peptide searches on 30 September 2026 and 10 skincare and collagen peptide searches plus 12 hair, GLP-1, safety and women's health peptide searches on 8 October 2026 in US English, and 40 of them showed the box. Tap a question to read our answer, with its sources.

  • 121 answered here
  • 4 not covered yet
  • 21 we don’t answer: dosing, mixing or buying

Tirzepatide 5 questions

TB-500 / thymosin beta-4 2 questions

Retatrutide 11 questions

BPC-157 13 questions

Semaglutide 14 questions

GHK-Cu / copper peptides 11 questions

Peptides in skincare 17 questions

Collagen peptides 13 questions

Peptides for hair 6 questions

Women, menopause & aging 9 questions

CJC-1295 / ipamorelin 4 questions

MOTS-c 4 questions

Legality & regulation 2 questions

Buying & vendors 6 questions

Reconstitution, units & calculators 5 questions

Weight loss 2 questions

Healing & recovery 1 question

Safety & side effects 9 questions

Peptides in general 12 questions

Source: Google’s “People also ask” boxes on page 1 of US-English results, collected 30 September 2026 and 8 October 2026. Searches that showed the box: on 30 September 2026, “are peptides legal”, “best peptide vendors”, “best peptides for healing”, “best peptides for weight loss”, “bpc-157”, “bpc-157 side effects”, “bpc-157 vs tb-500”, “cjc-1295 ipamorelin”, “ghk-cu”, “how to reconstitute peptides”, “mots-c”, “peptide therapy”, “research peptides”, “retatrutide”, “retatrutide vs tirzepatide”, “semaglutide units to mg”, “tb-500”, “where to buy retatrutide”; on 8 October 2026, “are peptides safe”, “argireline”, “collagen peptides”, “collagen peptides benefits”, “collagen supplements for skin”, “compounded semaglutide”, “compounded tirzepatide”, “copper peptides”, “copper peptides for hair”, “does collagen work”, “matrixyl”, “microdosing semaglutide”, “peptide injections”, “peptide serum”, “peptides for anti aging”, “peptides for hair growth”, “peptides for hair loss”, “peptides for menopause”, “peptides for skin”, “peptides for women”, “peptides side effects”, “what do peptides do for skin”. A question shown on more than one search counts once (157 shown, 146 different). Questions are quoted as Google showed them.

Evidence-graded · every claim sourced · updated 8 October 2026

Gray-market peptides, weighed against the evidence.

Plain-English notes on the peptides people buy outside the pharmacy. For each one: what it is, what studies in people show, whether it is legal, and what testers find in the vials. Every claim links to its source.

Start with Retatrutide Tirzepatide GHK-Cu BPC-157 NAD+ Glutathione

The 2026 briefingUpdated 8 Oct 2026 Research peptides in 2026: inside the gray-market boom US searches for “peptides” overtook “ozempic” in February 2026. Since then, FDA’s advisers have met and voted, but pharmacies still may not make most of the popular research peptides. Testers keep finding mislabeled vials, and more people report harm. Read the briefing

The vial shelf

Every compound we cover, drawn as a vial with its name and a dot for each amino acid. Illustrations only: no strength, no dose, no seller. See all 44 vials.

Guides to the big questions

Longer reads on questions that span many peptides, built on the compound pages and their sources.

What people send for testing

Test requests are one of the few public signals of which gray-market compounds people actually buy. They come from a self-selected, safety-minded US sample, so treat the order as a rough guide. Glutathione is not broken out in this data. We cover it anyway because wellness clinics, med spas and online peptide sellers all market it.

Share of 21,253 requests to Finnrick, a US testing service, May 2025 – May 2026
#CompoundRelative sizeShareTierStatus
1 Retatrutide 7,346 requests, 34.6% of 21,253 A Experimental · not approved anywhere
2 Tirzepatide 4,974 requests, 23.4% of 21,253 A FDA-approved (Zepbound, Mounjaro)
3 GHK-Cu 1,837 requests, 8.6% of 21,253 B Cosmetic ingredient · not an FDA-approved drug
4 BPC-157 1,376 requests, 6.5% of 21,253 B Not approved · US pharmacies may not make it · banned in sport
5 Tesamorelin 1,329 requests, 6.3% of 21,253 A FDA-approved (Egrifta SV, WR) for belly fat in HIV only
6 Ipamorelin 618 requests, 2.9% of 21,253 B Not approved · US pharmacies may not make it · banned in sport
7 TB-500 546 requests, 2.6% of 21,253 D Not approved · no human study found · pharmacies may not make it
8 Cagrilintide 485 requests, 2.3% of 21,253 A Experimental · CagriSema FDA decision expected late 2026
9 Semaglutide 434 requests, 2.0% of 21,253 A FDA-approved (Wegovy, Ozempic, Rybelsus)
10 CJC-1295 370 requests, 1.7% of 21,253 C Not approved · US pharmacies may not make it · banned in sport
11 PT-141 (bremelanotide) 290 requests, 1.4% of 21,253 A FDA-approved as Vyleesi · ‘PT-141’ vials not approved
12 Melanotan II 278 requests, 1.3% of 21,253 B Not approved · illegal to sell for human use in the US
13 Sermorelin 188 requests, 0.9% of 21,253 B No longer approved · made by US pharmacies · banned in sport
14 NAD+ 157 requests, 0.7% of 21,253 B Approved in China, not US · US pharmacies may make it for now
15 MOTS-c 154 requests, 0.7% of 21,253 D Not approved · US pharmacies may not make it · banned in sport

Not shown: 871 other or uncategorised requests (4.1%). Source: Finnrick Insights, “We’d Rather Buy the Future Than Wait For It” (published 5 May 2026, updated 10 Jun 2026); shares computed from the page’s chart data on 30 Sep 2026. finnrick.com

Every post, by what it is used for

44 compounds, each graded A to E on the strength of its human evidence. Compare them all in one table.

Weight loss

Weight lossA Retatrutide Retatrutide is an experimental weekly weight-loss injection from Eli Lilly. Large trials show major weight loss, but it is not approved anywhere, and vials sold online often fail tests. Experimental · not approved anywhere Weight lossA Tirzepatide Tirzepatide is a weekly injection for weight loss and type 2 diabetes, sold as Zepbound and Mounjaro. Trials show large weight loss, but “research” vials are illegal to sell for human use and often fail tests. FDA-approved (Zepbound, Mounjaro) Weight lossA Cagrilintide Cagrilintide is an experimental weekly injection from Novo Nordisk that caused large weight loss in trials when paired with semaglutide. As of 30 September 2026, it is not approved, and vials sold online often fail tests. Experimental · CagriSema FDA decision expected late 2026 Weight lossA Semaglutide Semaglutide, the drug in Ozempic and Wegovy, cut weight and the risk of heart attack, stroke or heart-related death in large trials. Unapproved “research” versions often fail tests. FDA-approved (Wegovy, Ozempic, Rybelsus) Weight lossB AOD-9604 AOD-9604 is a lab-made fragment of human growth hormone sold for fat loss. In its developer’s largest trial, of 502 adults, it did not beat placebo for weight loss, and it is not an approved medicine. Not approved · US pharmacies may not make it · banned in sport Weight lossA Liraglutide Liraglutide is the daily injection in Saxenda and Victoza. In large trials it cut weight, and in type 2 diabetes it lowered the risk of heart attack, stroke or heart-related death. In a head-to-head trial, weekly semaglutide cut more weight. FDA-approved (Saxenda, Victoza, generics) Weight lossA Mazdutide Mazdutide is a weekly weight-loss and diabetes injection, approved in China in 2025, not in the US. In a 48-week trial, Chinese adults with excess weight lost 11.0% to 14.0% of body weight, versus a 0.3% gain on placebo. Approved in China (Xinermei) · not in the US Weight lossA Orforglipron Orforglipron (Foundayo) is Eli Lilly’s daily weight-loss pill, FDA-approved in April 2026. It is not a peptide. On the top dose, adults lost 11.2% of their weight on average over 72 weeks, versus 2.1% on placebo. FDA-approved (Foundayo) · a daily pill, not a peptide Weight lossA Survodutide Survodutide is an experimental weekly weight-loss injection from Boehringer Ingelheim. In a 76-week trial, adults with obesity or overweight and no diabetes lost 12.2% to 13.0% of their weight, versus 5.4% on placebo. It is not approved anywhere. Experimental · not approved anywhere

Repair & recovery

Repair & recoveryB BPC-157 BPC-157 is a lab-made peptide sold for tendon, joint and gut healing. It is not approved anywhere, and the only placebo-controlled trial in patients that FDA found showed no clear benefit. Not approved · US pharmacies may not make it · banned in sport Repair & recoveryD TB-500 TB-500 is a lab-made piece of the body protein thymosin beta-4, sold online for injury recovery. FDA found no study that gave it to people and no animal safety studies. Not approved · no human study found · pharmacies may not make it Repair & recoveryE PEG-MGF PEG-MGF is sold online as a longer-lasting version of MGF, a lab-made peptide copied from part of a growth factor that muscles switch on when stretched. We found no published study of PEG-MGF itself in people or animals. Not approved · no human or animal study found · banned in sport Repair & recoveryD Pentadeca arginate (PDA) Pentadeca arginate (PDA) is sold by clinics and pharmacies as a more stable salt of BPC-157, made with the amino acid arginine. We found no published study of it in people; only a patent reports lab and animal tests. Not approved · no human study found · a salt form of BPC-157 Repair & recoveryA Thymosin beta-4 Thymosin beta-4 is a natural protein sold for injury recovery, often confused with TB-500, a lab-made piece of it. We found no trial of it on muscle or tendon injuries, and two large dry-eye trials found no clear benefit. Not approved · no injury trial found · pharmacies can’t make it

Skin & tanning

Skin & tanningB GHK-Cu GHK-Cu is a copper-carrying peptide used in skin creams and now often injected. Small skin trials had mixed results, and we found no published study that injected it on its own in people. Cosmetic ingredient · not an FDA-approved drug Skin & tanningB Melanotan II Melanotan II is a lab-made tanning peptide sold online as injections and nasal sprays. It is not approved, we found only three tiny human studies of it, and case reports link it to melanoma. Not approved · illegal to sell for human use in the US Skin & tanningA Melanotan I (afamelanotide) Melanotan I is afamelanotide, approved as Scenesse, an implant for a rare disorder that makes sunlight painful. Small trials found it darkens skin, but ‘MT1’ vials sold online for tanning are not approved. FDA-approved as Scenesse · ‘Melanotan I’ vials not approved

Growth hormone axis

Growth hormone axisA Tesamorelin Tesamorelin boosts growth hormone and is FDA-approved only for excess belly fat in adults with HIV. Other uses have little evidence, and vials sold online often fail tests. FDA-approved (Egrifta SV, WR) for belly fat in HIV only Growth hormone axisB Ipamorelin Ipamorelin is a lab-made peptide that triggers short bursts of growth hormone. Its only published patient trial found no clear benefit, and we found no study testing it in people for fat loss, muscle or sleep. Not approved · US pharmacies may not make it · banned in sport Growth hormone axisC CJC-1295 CJC-1295 is a lab-made version of a brain hormone that makes the body release growth hormone. It is not approved in the US or Europe, and we found no published study of fat loss, muscle or healing in people. Not approved · US pharmacies may not make it · banned in sport Growth hormone axisB Sermorelin Sermorelin is a lab-made piece of a brain hormone that tells the body to release growth hormone. Once approved in the US for children, it was discontinued in 2008, and its studies in adults are small and short. No longer approved · made by US pharmacies · banned in sport Growth hormone axisB GHRP-2 (pralmorelin) GHRP-2 is a lab-made peptide that makes the body release growth hormone. Japan approved it in 2004 as a one-dose test for growth hormone deficiency. We found no trial of it for muscle gain or fat loss. Approved in Japan, not the US · US pharmacies may not make it Growth hormone axisB GHRP-6 GHRP-6 was one of the first lab-made peptides shown to make the body release growth hormone. It is not approved in the US, and we found no trial of it for muscle gain or fat loss. Not approved · US pharmacies may not make it · banned in sport Growth hormone axisB Hexarelin Hexarelin, a lab-made peptide that makes the body release growth hormone, briefly made the heart pump harder in small one-dose studies. It is not approved in the US, and we found no controlled trial of it for muscle gain. Not approved · US pharmacies may not make it · banned in sport Growth hormone axisB MK-677 (ibutamoren) MK-677 is an experimental pill, not a peptide, that makes the body release more growth hormone. In older adults it added lean mass but not strength and raised blood sugar; a hip-fracture trial stopped early over a heart failure signal. Not approved · US pharmacies may not make it · banned in sport

Sexual health

Sexual healthA PT-141 (bremelanotide) PT-141 is bremelanotide, approved in the US as Vyleesi for low sexual desire in women before menopause. It helps a little, nausea is common, and ‘PT-141’ vials sold online are not approved. FDA-approved as Vyleesi · ‘PT-141’ vials not approved Sexual healthB Gonadorelin Gonadorelin is a lab-made copy of the brain hormone that tells the pituitary gland to switch on the testes and ovaries. Pump pulses helped women ovulate, but we found no published trial of it in men on testosterone therapy. Cattle-only approval · pharmacy-made · banned for male athletes Sexual healthB Kisspeptin Kisspeptin is a natural hormone that switches on the body’s reproductive system. In brief human studies it raised sex hormones and arousal measures, but it is not approved for any use and US pharmacies may not make it. Experimental · not approved · US pharmacies may not make it

Longevity & wellness

Longevity & wellnessB NAD+ NAD+ is a helper molecule cells use to make energy, not a peptide. Clinics sell it as IV drips and shots for energy and anti-aging; 2026 reviews found no good evidence for those uses, and contaminated products have sickened people. Approved in China, not US · US pharmacies may make it for now Longevity & wellnessD MOTS-c MOTS-c is a peptide the body makes, coded in the DNA of mitochondria, the cell’s power plants. Injections helped mice resist weight gain and run better, but FDA found no published study that gave it to people. Not approved · US pharmacies may not make it · banned in sport Longevity & wellnessB Epitalon Epitalon is a lab-made peptide of four amino acids, sold for longevity, telomeres and sleep. Most of its research comes from one Russian group, and we found no controlled trial testing whether it slows aging in people. Not approved · US pharmacies may not make it · sport ban likely Longevity & wellnessB Glutathione Glutathione is a natural antioxidant the body makes from three amino acids. Clinics sell drips and shots for lighter skin and wellness, but trials give little support. In 2026, contaminated pharmacy vials sickened dozens of people. Not approved as a drug · US pharmacies may make it for now Longevity & wellnessB SS-31 (elamipretide) SS-31 is elamipretide, a lab-made peptide aimed at mitochondria, the cell’s power plants. FDA approved it in 2025 as Forzinity for a rare genetic disease. Most trials missed their main goals, and ‘SS-31’ vials sold online are not approved. FDA-approved as Forzinity · ‘SS-31’ vials not approved

Brain & sleep

Brain & sleepB Cerebrolysin Cerebrolysin is an injectable drug made from digested pig brain: a mixture of small peptides and amino acids. It is approved in parts of Europe but not the US, and reviews of its trials find small or uncertain benefits. Approved abroad, not in the US · US pharmacies may not make it Brain & sleepD Dihexa Dihexa is a lab-made compound designed to help brain cells form new connections. We found no study that gave dihexa itself to people, and a key paper behind it was retracted for falsified data. Experimental · no human study found · not approved Brain & sleepB DSIP (emideltide) DSIP is a lab-made copy of a 9-amino-acid peptide first found in rabbits, sold online for sleep. Small trials from 1981 to 1992 disagreed, and two independent placebo-controlled trials found little or no benefit. Approved in Russia, not US · US pharmacies may not make it Brain & sleepA Oxytocin Oxytocin is a pituitary hormone approved in the US as Pitocin, a hospital injection for labor and bleeding after birth. Nasal sprays sold for bonding, calm and libido rest on mostly small trials with mixed results. FDA-approved as Pitocin · nasal sprays and vials not approved Brain & sleepB Selank Selank is a lab-made chain of 7 amino acids built from tuftsin, a small immune peptide, and sold in Russia as nose drops for anxiety. Its anxiety evidence comes from small Russian trials without a placebo group. Approved in Russia, not the US · US pharmacies may not make it Brain & sleepB Semax Semax is a lab-made chain of 7 amino acids: part of the stress hormone ACTH plus a 3-amino-acid tail. Russia sells it as nose drops for stroke and memory problems. Its human evidence is small and mostly Russian. Approved in Russia, not the US · US pharmacies may not make it

Immune

ImmuneD KPV KPV is a lab-made peptide of three amino acids, copied from the tail of a hormone that calms inflammation. It is sold for gut and skin problems, but FDA found no study of it in people. Experimental · not approved · US pharmacies may not make it ImmuneB LL-37 LL-37 is a lab-made copy of a peptide the immune system makes to kill bacteria. A gel version missed its main goal in a 149-person ulcer trial, and we found no trial of it as a general immune booster. Not approved · pharmacies may not make it · tested on wounds ImmuneB Thymalin Thymalin is a Russian prescription drug made from calf thymus glands: a mix of small peptides, not one molecule. Its human trials are small and mostly run by its developers, and it is not approved in the US. Approved in Russia, not the US · US pharmacies may not make it ImmuneA Thymosin alpha-1 Thymosin alpha-1 is a lab-made copy of a natural peptide first found in the thymus, sold abroad as Zadaxin. Large trials in sepsis and severe pancreatitis found no benefit, and US pharmacies may not make it. Approved abroad, not by FDA · US pharmacies may not make it ImmuneB VIP (vasoactive intestinal peptide) VIP is a natural nerve peptide sold in the US as a pharmacy-made nasal spray for mold illness (CIRS). We found no test of that use against a placebo. As the drug aviptadil, it failed a large COVID-19 trial. Approved abroad, not by FDA · US pharmacies may make it for now

How to read this blog

  1. ATwo or more large human trials
  2. BAt least one controlled human trial
  3. COnly small or uncontrolled human studies
  4. DAnimal studies only
  5. ELab or anecdotal evidence only

Each post keeps three kinds of dose information apart: doses given in human studies, doses used in animal studies, and what users report. Only the first comes from controlled research. Read how we grade evidence.