What Are Peptides?
Fact-checked against FDA and official sources · Not yet reviewed by a licensed clinician. How we check facts
Peptides are short chains of amino acids, the tiny building blocks of protein. Your body makes many of them, like insulin, and some are medicines, like semaglutide (Ozempic, Wegovy). You see them everywhere in 2026 because of weight-loss shots, social media posts and clinic ads. But not every peptide is proven, and not every one is safe.
Quick answer: 3 kinds you will see
What are peptides made of?
Peptides are made of amino acids. Think of amino acids as beads. Put 2 to about 50 beads on a string, and you have a peptide. A much longer string folds up into a protein. That is how the NIH's genome institute explains it.
Your body makes lots of peptides. Insulin helps sugar get into your cells. Oxytocin helps during birth. GLP-1 helps tell your brain you are full.
Some medicines are lab-made copies of body peptides. Semaglutide is about 94% the same as your own GLP-1, says its FDA label. More than 80 peptide drugs have reached the market since insulin, says a 2021 science review.
Why is everyone talking about peptides in 2026?
- Weight-loss shots. Wegovy and Zepbound are peptide drugs. They made the word "peptide" famous.
- Social media. Posts call BPC-157 and others "healing" or "anti-aging," mostly based on animal tests.
- Clinics and online shops. Many now sell "wellness" peptides.
- FDA news. FDA advisers met about some peptides in July 2026. On October 28, 2026, HHS issued an interim policy that covers 6 pharmacy-made peptides, like BPC-157, with a prescription. It is not FDA approval. See our peptide policy tracker.
The hard part is telling hype from proof. That is what this page is for.
How do peptides work in your body?
Most peptides are messengers. A peptide travels to a cell and fits into a spot on it called a receptor, like a key in a lock. Then the cell does a job, like making you feel full or letting sugar in.
Each key fits only certain locks, so most peptides do one main job.
Your stomach breaks most peptides apart, just like it breaks down food. That is why most peptide medicines are shots, not pills.
Peptides vs proteins vs steroids
| Peptides | Proteins | Steroids | |
|---|---|---|---|
| Made of | Short chains of amino acids | Long chains of amino acids, folded up | Rings of carbon, no amino acids |
| Size | About 2 to 50 amino acids | More than 50, often hundreds | Small, different shape |
| Examples | Insulin, GLP-1, semaglutide, BPC-157 | Meat, eggs, muscle, collagen | Testosterone, cortisone, anabolic steroids |
| Banned in sports? | Many peptide hormones are on WADA's banned list | Food protein is not banned | Anabolic steroids are banned |
So peptides are not steroids. But some are still banned in sports. More in Are peptides steroids?
Peptides in food and collagen
When you eat protein, your gut cuts it into small peptides and amino acids. These are fuel and building blocks, not medicine.
Collagen peptides are bits of collagen protein from animal skin or bone. They are sold as supplements. The FDA does not approve supplements before they are sold.
Do they work? For skin, the best-run studies showed no clear effect. For knee pain, a 2025 review found it may help a little. See Are collagen peptides the same as peptides?
The 4 kinds of peptides you will see
1. Your body's own peptides
FDA status: FDA: Does not applyProof it works: Proof: Known jobs in the bodySafety data: Safety data: Normal at body levelsInsulin, oxytocin and GLP-1. They run jobs like blood sugar, birth and hunger.
2. FDA-approved peptide drugs
FDA status: FDA: ApprovedProof it works: Proof: Strong for most approved usesSafety data: Safety data: Mostly well studiedExamples: semaglutide, tirzepatide, teriparatide (bones), bremelanotide (low desire in women). Approved for set uses only. Full list.
3. Supplements and creams
FDA status: FDA: Not approved before saleProof it works: Proof: MixedSafety data: Safety data: LimitedCollagen powders and peptide skin creams. The FDA does not check these before they are sold.
4. Unapproved "research" peptides
FDA status: FDA: Not approvedProof it works: Proof: Animal or early studies onlySafety data: Safety data: Very littleExamples: BPC-157, TB-500, CJC-1295, ipamorelin. Popular online, barely tested in people. Labeled "research use only," which means not for people.
"Not FDA approved" means no company proved to the FDA that it is safe and works. It does not tell you if it works, and it does not, by itself, make owning it a crime. The rules are mostly about selling and making it. See Are peptides legal in the US?
Popular peptides by goal
The peptides people ask about most, by goal. Proof is rated for the use shown. No doses, no sellers.
| Peptide | FDA status | Proof in people | Safety data |
|---|---|---|---|
| Weight loss | |||
| GLP-1: Wegovy / Ozempic (semaglutide) | FDA approved | Strong for weight loss | Well studied |
| GLP-1: Zepbound / Mounjaro (tirzepatide) | FDA approved | Strong for weight loss | Well studied |
| GLP-1: Retatrutide | In testing | Strong for weight loss | Limited |
| AOD-9604 | Not approved | Animal or lab only for fat loss | Very little |
| Muscle and recovery | |||
| BPC-157 | Not approved | Early for healing injuries and pain | Very little |
| TB-500 | Not approved | Animal or lab only for muscle and injury recovery | Very little |
| Ipamorelin | Not approved | None found for muscle, sleep, or anti-aging | Limited |
| Skin and tanning | |||
| GHK-Cu | Not approved | Early for younger-looking skin | Very little |
| Melanotan II | Not approved | Early for tanning | Very little |
| Scenesse (afamelanotide) | FDA approved | Some for light pain in the rare disease EPP | Limited |
| Sex drive | |||
| Vyleesi (bremelanotide, PT-141) | FDA approved | Some for low sexual desire in women before menopause | Well studied |
| Kisspeptin-10 | Not approved | Early for raising testosterone or fertility | Very little |
| Sleep, worry and focus | |||
| DSIP (emideltide) | Not approved | Early for sleep | Very little |
| Selank | Not approved | Early for stress and worry | Very little |
| Aging | |||
| Epitalon | Not approved | Animal or lab only for slowing aging | Very little |
Compare two with our comparison tool, or try Is there a peptide for my goal? By goal: joint pain, hair, gut, libido, sleep and brain fog, menopause, aging.
Are peptides the same as GLP-1s?
No, but they overlap. GLP-1 drugs like semaglutide (Wegovy, Ozempic) and liraglutide (Saxenda) are peptides. Tirzepatide (Zepbound, Mounjaro) is a peptide too. It acts on GLP-1 and one more hormone.
These peptide drugs were tested in big trials with a placebo (fake shot) group. Here is how much weight adults lost on average:
Weight loss in big obesity drug trials
% of starting body weight lost, drug vs placebo (fake shot)
Tirzepatide 15 mg (Zepbound)SURMOUNT-1 · 2,539 adults · 72 weeks
Semaglutide 2.4 mg (Wegovy)STEP 1 · 1,961 adults · 68 weeks
Liraglutide 3.0 mg (Saxenda)SCALE · 3,731 adults · 56 weeks
Different trials, different people: not a head-to-head comparison.
Show the numbers as a table
| Trial | Drug | Placebo |
|---|---|---|
| Tirzepatide 15 mg (Zepbound) SURMOUNT-1 · 2,539 adults · 72 weeks | −20.9% | −3.1% |
| Semaglutide 2.4 mg (Wegovy) STEP 1 · 1,961 adults · 68 weeks | −14.9% | −2.4% |
| Liraglutide 3.0 mg (Saxenda) SCALE · 3,731 adults · 56 weeks | −7.4% | −3.0% |
But most peptides are not GLP-1s. BPC-157 and TB-500 are not GLP-1 drugs and do not work the same way. And one new GLP-1 pill, orforglipron (Foundayo), is not a peptide at all. It is a small lab-made molecule.
The FDA warns about unapproved "GLP-1" products sold online. Read more: GLP-1: what it is and the full drugs list, Peptides vs GLP-1 and Is Zepbound a GLP-1?
How are peptides taken?
- Shots under the skin. This is the most common way, because the stomach breaks most peptides down.
- Pills. Only a few work. Semaglutide pills (Rybelsus, Wegovy tablets) use a helper ingredient so some gets through.
- Nose sprays. A few approved peptide drugs, like desmopressin, come as sprays.
- Creams. Many skin creams list peptides. These are usually sold as cosmetics, which do not need FDA approval.
Are peptides safe?
Approved peptide drugs were tested in thousands of people, and their labels list side effects. For GLP-1 drugs, the most common are stomach problems like nausea.
Peptides sold online: we mostly do not know. The FDA says it has little or no safety data in people for many, like BPC-157, and some may cause an immune reaction. "Research use only" vials are not checked for purity.
Be extra careful if you are pregnant, under 18, or have had cancer. Read Are peptides safe? and use our side effects checker.
Are peptides legal in the US right now?
FDA-approved peptide drugs are legal with a prescription. Many popular "wellness" peptides are not FDA approved. The FDA lists some, like ipamorelin and kisspeptin-10, in "Category 2." That is a list of ingredients that may be too risky for pharmacies to mix into medicine. See the Category 2 list.
New on October 28, 2026: HHS issued an interim policy. Licensed pharmacies may make 6 peptides (BPC-157, TB-500, KPV, MOTS-c, Semax and epitalon) for a patient with a prescription, under strict rules. They are still not FDA approved, and "research use only" products are still not medicine.
Questions to ask before you try a peptide
- Is it FDA approved for what I want? (Check here)
- What proof is there in people, not just animals?
- What are the side effects, and what is unknown?
- Will it mix badly with my other medicines or health problems?
- Where does it come from? Is it a licensed US pharmacy with a prescription? (Is my source legit?)
- Will it show up on a sports drug test?
Take these to your doctor. Print our doctor questions sheet.
Real studies, in plain words
| Study | People | What it found |
|---|---|---|
| STEP 1 trial, semaglutide (NEJM 2021) | 1,961 adults with obesity or overweight | Lost about 15% of body weight in 68 weeks, vs 2.4% with a fake shot (placebo). |
| SURMOUNT-1 trial, tirzepatide (NEJM 2022) | 2,539 adults with obesity or overweight | Lost about 15% to 21% of body weight in 72 weeks, vs 3.1% with placebo. |
| Collagen and skin review (Am J Med 2025) | 23 trials, 1,474 people | Helped skin overall, but the best studies and those not paid for by companies showed no clear effect. |
| Collagen and knee arthritis review (Clin Exp Rheumatol 2025) | 11 trials, 870 people | Improved knee pain and movement scores vs placebo. |
| BPC-157 in people review (Acta Orthop Belg 2026) | 3 small studies, 30 people | Most felt better, but no study had a placebo group. Proof rated very low. |
How many people each peptide was tested in
Biggest study in people we list for each one (log scale, so small numbers still show)
GLP-1: Wegovy / Ozempic (semaglutide)FDA approvedSELECT heart trial
GLP-1: Trulicity (dulaglutide)FDA approvedREWIND heart trial
GLP-1: Saxenda / Victoza (liraglutide)FDA approvedSCALE
Cagrilintide (part of CagriSema)In testingREDEFINE 1 (with semaglutide)
GLP-1 pill: Foundayo (orforglipron)FDA approvedATTAIN-1 · not a peptide
GLP-1: Zepbound / Mounjaro (tirzepatide)FDA approvedSURMOUNT-1
Tymlos (abaloparatide)FDA approvedACTIVE
GLP-1: RetatrutideIn testingTRIUMPH-1
Forteo (teriparatide)FDA approvedFracture trial
Vyleesi (bremelanotide, PT-141)FDA approvedRECONNECT (2 trials)
Thymosin alpha-1Not FDA approvedTESTS sepsis trial · no benefit
Egrifta (tesamorelin)FDA approvedBelly fat trial
IpamorelinNot FDA approvedPhase 2 (gut, after surgery)
SemaxNot FDA approvedNot randomized
SelankNot FDA approvedSmall randomized study
BPC-157Not FDA approvedAll 3 small studies added up
GHK-CuNot FDA approvedSkin product trial
TB-500Not FDA approvedNo study of TB-500 itself
KPVNot FDA approvedMice only
MOTS-cNot FDA approvedMice only
AOD-9604Not FDA approvedRats only
The popular online peptides were tested in tens of people, or none. The approved drugs were tested in thousands.
Show the numbers as a table
| Peptide | People in the study |
|---|---|
| GLP-1: Wegovy / Ozempic (semaglutide) (FDA approved) SELECT heart trial | 17,604 people |
| GLP-1: Trulicity (dulaglutide) (FDA approved) REWIND heart trial | 9,901 people |
| GLP-1: Saxenda / Victoza (liraglutide) (FDA approved) SCALE | 3,731 people |
| Cagrilintide (part of CagriSema) (In testing) REDEFINE 1 (with semaglutide) | 3,417 people |
| GLP-1 pill: Foundayo (orforglipron) (FDA approved) ATTAIN-1 · not a peptide | 3,127 people |
| GLP-1: Zepbound / Mounjaro (tirzepatide) (FDA approved) SURMOUNT-1 | 2,539 people |
| Tymlos (abaloparatide) (FDA approved) ACTIVE | 2,463 people |
| GLP-1: Retatrutide (In testing) TRIUMPH-1 | 2,339 people |
| Forteo (teriparatide) (FDA approved) Fracture trial | 1,637 people |
| Vyleesi (bremelanotide, PT-141) (FDA approved) RECONNECT (2 trials) | 1,267 people |
| Thymosin alpha-1 (Not FDA approved) TESTS sepsis trial · no benefit | 1,106 people |
| Egrifta (tesamorelin) (FDA approved) Belly fat trial | 412 people |
| Ipamorelin (Not FDA approved) Phase 2 (gut, after surgery) | 114 people |
| Semax (Not FDA approved) Not randomized | 110 people |
| Selank (Not FDA approved) Small randomized study | 70 people |
| BPC-157 (Not FDA approved) All 3 small studies added up | 30 people |
| GHK-Cu (Not FDA approved) Skin product trial | 13 people |
| TB-500 (Not FDA approved) No study of TB-500 itself | 0 people |
| KPV (Not FDA approved) Mice only | 0 people |
| MOTS-c (Not FDA approved) Mice only | 0 people |
| AOD-9604 (Not FDA approved) Rats only | 0 people |
Keep reading
- Why are peptides so popular right now? The trends, the FDA plan and the hype, in one place.
- FDA peptide plan: all White House meetings and timeline, with dates.
- Longevity peptides: anti-aging claims checked against FDA status, proof and safety.
- Are collagen peptides the same as peptides? And peptides for thyroid and Hashimoto's.
- Peptides you may not know: oxytocin (Pitocin), pramlintide (Symlin), IGF-1 LR3 and Cerebrolysin.
FAQ
Do peptides show up on a drug test?
A standard US DOT work test looks only for marijuana, cocaine, amphetamines, opioids and PCP. Sports tests are different. Try our drug test checker.
Do I need a prescription for peptides?
Yes, for FDA-approved peptide drugs. A pharmacy can mix (compound) one only with a prescription and an allowed ingredient. See Can a doctor prescribe peptides?
Do peptide creams work?
Proof is thin. GHK-Cu, a common cream peptide, has only early studies in people. If a cream claims to change how your body works, the FDA treats it as a drug.
Do peptides expire?
Yes. Approved peptide medicines have a tested expiration date on the label. "Research use only" vials do not. See Do peptides expire?
Can I fly with peptides?
Usually, with medicine you need. TSA allows medical liquids over 3.4 ounces and their syringes. That does not make a product legal. See Flying with peptides.
Can peptides cause cancer?
There is no proof that wellness peptides start cancer in healthy people. Cancer centers worry some might help an existing tumor grow. See Can peptides cause cancer?
Sources
- NIH National Human Genome Research Institute: Peptide (definition, 2 to 50 amino acids)
- PubMed: Muttenthaler et al., Trends in peptide drug discovery (more than 80 peptide drugs on the market), Nat Rev Drug Discov 2021
- PubMed: Fosgerau & Hoffmann, Peptide therapeutics: current status and future directions, Drug Discov Today 2015
- DailyMed (FDA label): Wegovy (semaglutide) injection and tablets, incl. 94% match to human GLP-1
- DailyMed (FDA label): Zepbound (tirzepatide)
- DailyMed (FDA label): Rybelsus / Ozempic tablets (semaglutide)
- DailyMed (FDA label): Desmopressin acetate nasal spray
- DailyMed (FDA label): Vyleesi (bremelanotide)
- PubMed: Wilding et al., Once-weekly semaglutide in adults with overweight or obesity (STEP 1), NEJM 2021
- PubMed: Jastreboff et al., Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1), NEJM 2022
- PubMed: Wharton et al., Orforglipron, an oral small-molecule (nonpeptide) GLP-1 drug for obesity (ATTAIN-1), NEJM 2025
- PubMed: Myung & Park, Effects of collagen supplements on skin aging: meta-analysis of 23 randomized trials, Am J Med 2025
- PubMed: Simental-Mendía et al., Collagen supplementation for knee osteoarthritis: meta-analysis of 11 randomised trials, Clin Exp Rheumatol 2025
- PubMed: Poolton et al., Human evidence for BPC-157: a systematic review, Acta Orthop Belg 2026
- FDA: Bulk drug substances that may present significant safety risks (Category 2 and withdrawn lists)
- FDA: July 23-24, 2026 Pharmacy Compounding Advisory Committee meeting
- Reginfo.gov: Interim Access Policy for Compounding Using Certain Peptides (RIN 0910-ZD94), under OMB review
- FDA: Concerns with unapproved GLP-1 drugs used for weight loss
- FDA: Questions and answers on dietary supplements (FDA does not approve supplements before sale)
- FDA: Is it a cosmetic, a drug, or both?
- WADA: Prohibited List (S2 peptide hormones)
- eCFR: 49 CFR 40.82, what drugs DOT tests look for