The Peptide Dictionary
Every peptide word, decoded.
Whether it is a skin serum, a sleep aid, or a weight-loss shot, every term is explained in simple, everyday words a fifth grader could follow.
128 terms10 categoriesAlways free
How to read this dictionary. These words are defined so you understand what you see online — not as instructions. peptides.io does not tell anyone to mix, dose, or inject anything. Research and unapproved peptides are meant for qualified laboratory research, not for people to use on themselves. Always talk to a licensed provider, and never use or inject anything that was not prescribed to you.
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The Basics
What peptides are, and the science words behind them.
Peptide
A short chain of amino acids. Think of it as a small piece of protein that acts like a messenger.
The doctor said the new weight-loss shot is a peptide — just a tiny piece of protein that carries a message in your body.
Amino acid
A tiny building block. Your body uses about 20 of them to make everything from muscle to hormones.
The protein in your food gets broken down into amino acids, the little building blocks your body reuses.
Protein
A long chain of amino acids, usually more than 50. A peptide is the short version of the same idea.
A protein is a long chain of amino acids; a peptide is like a short snippet of that same chain.
Peptide hormone
A hormone that is made of a peptide. Insulin is the best-known example.
Insulin is a peptide hormone — a body messenger that happens to be made of a small chain of amino acids.
Receptor
A spot on a cell that a signal locks onto, like a keyhole waiting for the right key.
The hormone floats around until it finds its receptor, the little keyhole on a cell that it fits into.
Receptor agonist
Something that fits a receptor and switches it on, the way a key turns a lock.
Semaglutide is a receptor agonist: it fits the GLP-1 keyhole and switches it on, just like the real gut hormone would.
Antagonist
The opposite of an agonist. It blocks a receptor so a signal cannot switch it on.
If an agonist flips a switch on, an antagonist is the tape that keeps the switch from moving.
GLP-1
Short for glucagon-like peptide-1, a gut hormone released after you eat. It helps manage blood sugar and appetite.
After a big meal, your gut releases GLP-1, a hormone that tells your brain you are full and helps steady your blood sugar.
GIP
Short for glucose-dependent insulinotropic polypeptide, another gut hormone that works alongside GLP-1.
Tirzepatide copies two gut hormones at once: GLP-1 and its teammate, GIP.
Incretin
The nickname for gut hormones like GLP-1 and GIP that help your body handle food after you eat.
GLP-1 and GIP are called incretins because they kick in right after a meal.
Dual agonist
A medicine that switches on two receptors at once. Tirzepatide acts on both GIP and GLP-1.
Because it turns on two receptors instead of one, tirzepatide is called a dual agonist.
Analog
A lab-made copy of a natural peptide, tweaked so it lasts longer or works harder in the body.
Semaglutide is an analog of the gut hormone GLP-1, rebuilt to last about a week instead of a few minutes.
Secretagogue
Something that tells your body to release a hormone it already makes, instead of adding the hormone itself.
Sermorelin is a secretagogue: it nudges your body to make its own growth hormone.
Peptide bond
The chemical link that joins one amino acid to the next to build the chain.
Every peptide bond is like a link snapping two amino acids together into a chain.
Amino acid sequence
The exact order of amino acids in a peptide. Change the order and you change what it does.
A peptide’s sequence is like the letters in a word: rearrange them and it means something different.
Synthetic peptide
A peptide built in a lab instead of taken from a plant or animal.
Almost every peptide you read about is synthetic, meaning it is made in a lab.
Endogenous vs exogenous
Endogenous means made inside your body. Exogenous means it comes from outside, like from a shot.
The GLP-1 your gut makes is endogenous; the GLP-1 in a weight-loss pen is exogenous.
Titration
Starting a dose low and raising it slowly over weeks, so your body has time to adjust.
To avoid an upset stomach, the plan uses titration — you start low and step the dose up slowly over a few weeks.
Half-life
The time it takes for the amount of a drug in your body to drop by half. Semaglutide, for example, has a long half-life of about one week.
Semaglutide has a long half-life of about a week, which is why a single shot keeps working for seven days.
Bioavailability
How much of a dose actually reaches your bloodstream. Peptides swallowed as plain pills often have low bioavailability.
A peptide swallowed as a plain pill has low bioavailability, because your stomach breaks most of it down before it can work.
Peptide therapy
A marketing term for treatments that use peptides, often at wellness or anti-aging clinics. The specific peptides used range from FDA-approved to not approved.
The clinic advertises peptide therapy for recovery and energy.
Weight-Loss Shots
The GLP-1 medicines behind the weight-loss headlines.
Semaglutide
A GLP-1 medicine. Wegovy® is approved for weight management, while Ozempic® and Rybelsus® are approved for type 2 diabetes. Rybelsus® is the pill form.
Her doctor prescribed semaglutide; the same medicine is sold as Wegovy for weight and Ozempic for diabetes.
Tirzepatide
A dual GIP and GLP-1 medicine. Zepbound® is approved for weight management, and Mounjaro® is approved for type 2 diabetes.
He switched to tirzepatide — sold as Zepbound for weight and Mounjaro for diabetes — because it copies two gut hormones.
Liraglutide
An older, daily GLP-1 medicine. Saxenda® is approved for weight management, and Victoza® is approved for type 2 diabetes.
Before the once-a-week shots, there was liraglutide (Saxenda and Victoza), an older version you take once a day.
Retatrutide
An experimental weight-loss drug that copies three hormones at once (GLP-1, GIP, and glucagon). As of 2026 it is still in clinical trials and is not FDA-approved.
Retatrutide is a “triple” shot still being tested in trials; it is not FDA-approved yet.
Ozempic face
A nickname for the hollow, older-looking face that can come from losing weight quickly. It is about fast weight loss, not the drug itself.
People call the sunken look from fast weight loss “Ozempic face,” though any quick weight loss can do it.
Ozempic
The brand name for semaglutide when it is used for type 2 diabetes. It is a weekly shot that lowers blood sugar, and many people also lose weight on it.
My doctor put me on Ozempic to help my blood sugar.
Wegovy
The same drug as Ozempic (semaglutide), just at a higher dose that is approved for weight loss.
She has lost 30 pounds on Wegovy.
Mounjaro
The brand name for tirzepatide used for type 2 diabetes. It is a weekly shot that copies two gut hormones at once.
He takes Mounjaro for his diabetes.
Zepbound
The same drug as Mounjaro (tirzepatide), approved for weight loss and for sleep apnea.
Zepbound helped him lose weight and sleep better.
Rybelsus
Semaglutide made as a daily pill instead of a shot.
I take Rybelsus every morning so I do not have to inject.
Saxenda
The brand name for liraglutide used for weight loss. It is an older, once-a-day GLP-1 shot.
Before Wegovy, my aunt used Saxenda.
Victoza
Liraglutide used for type 2 diabetes. It is the same drug as Saxenda, at a lower dose.
He was on Victoza for years before the newer shots came out.
Trulicity
A once-a-week GLP-1 shot for type 2 diabetes. Its drug name is dulaglutide.
Her diabetes is managed with Trulicity.
GLP-1 receptor agonist
The medical name for the whole family of drugs like Ozempic and Wegovy. They copy the gut hormone GLP-1 that tells you that you are full.
Ozempic and Mounjaro are both GLP-1 receptor agonists.
Orforglipron (Foundayo)
A once-a-day weight-loss pill you can take any time, with or without food. It works like the GLP-1 shots but is a pill, and is technically not a peptide.
I would rather take the Foundayo pill than inject.
Cagrilintide / CagriSema
Cagrilintide copies a fullness hormone called amylin. CagriSema pairs it with semaglutide in one shot. Both are still being tested and are not FDA-approved.
CagriSema is one of the next weight-loss drugs being tested.
Survodutide
An experimental weight-loss shot that works on two targets, GLP-1 and glucagon. Not FDA-approved.
Survodutide is still in late-stage testing.
Mazdutide
An experimental weight-loss shot, furthest along in China. Not FDA-approved in the U.S.
Mazdutide is being developed mainly for the China market.
Side Effects & Slang
The everyday words people use for how the shots feel and what they call them.
Food noise
The constant, hard-to-ignore thinking and craving about food. Many people say the GLP-1 shots make this noise go quiet.
The food noise stopped a week after my first shot.
Ozempic butt
A nickname for loose or saggy skin on the backside after losing weight fast. It is about quick weight loss, not the drug itself.
I lost the weight, but now I have what people call Ozempic butt.
Sulfur burps
Burps that smell like rotten eggs. They can happen because these drugs slow the stomach down.
The sulfur burps were the worst part of my first month.
Skinny shot
An everyday nickname for the GLP-1 drugs like Ozempic and Wegovy. It is slang, not a brand or a medical name.
She got the skinny shot at a med spa.
Gastroparesis
A stomach that empties too slowly, which causes nausea and feeling full fast. GLP-1 drugs can cause or worsen it.
Her doctor checked for gastroparesis after months of nausea.
Weight-loss plateau (stall)
A point where the scale stops moving even though you are still on the shot. It is a normal part of weight loss.
I hit a stall at month four and worried something was wrong.
Non-responder
A person who loses little or no weight on a GLP-1 drug. It happens to some people.
About one in seven people are non-responders to these shots.
GLP-1 microdosing
Taking a smaller dose than the label says, to save money or ease side effects. It is a trend online, not something the FDA studied or recommends.
People online talk about microdosing their Ozempic pen.
Skin & Beauty
Peptides used on skin — the ones in serums and powders.
GHK-Cu
The copper peptide in skin serums. The best-studied peptide for skin, used in creams and serums rather than as a medicine.
She bought a serum with GHK-Cu, the copper peptide that is the best-studied one for skin.
Collagen peptide
Collagen broken into short chains, sold as a supplement powder for skin and joints. It is a food product, not a drug.
He stirs a scoop of collagen peptide powder into his coffee; it is sold as a food supplement, not a medicine.
Melanotan II
An injected peptide that darkens the skin for a tan. Not FDA-approved, and regulators have flagged it as unsafe.
She used Melanotan II to get tan without the sun.
Signal peptide
A skincare peptide that tells skin cells to make more collagen. It is a cosmetic ingredient, not a drug.
This serum uses a signal peptide to firm the skin.
Matrixyl
A popular anti-aging skincare peptide that nudges the skin to build more collagen. A cosmetic ingredient, not a drug.
My night cream has Matrixyl for fine lines.
Argireline
A skincare peptide sold as “Botox in a bottle” that tries to relax tiny face muscles. It is not real Botox and not a drug.
The eye cream with Argireline softens crow’s-feet.
Carrier peptide
A skincare peptide that carries a helpful mineral, like copper, into the skin.
GHK-Cu is a carrier peptide that delivers copper.
Healing & Recovery
Research peptides people talk about for healing.
BPC-157
A lab-made peptide copied from a protein your stomach makes. Studied mostly in animals for healing. Not FDA-approved.
BPC-157 gets a lot of buzz online for healing, but it has mostly been tested in animals and is not FDA-approved.
TB-500
A lab-made piece of a natural repair protein, studied for recovery, mostly in animals. Not FDA-approved.
Some athletes talk about TB-500 for recovery, though it is a research peptide, not an approved medicine.
KPV
A peptide made of just three protein building blocks, studied for calming redness and swelling. Its letters spell its name: K, P, V. Not FDA-approved.
KPV is a tiny three-letter peptide studied for calming redness, but there are no approved products you can buy.
Thymosin alpha-1
A peptide studied to help support the immune system. Not FDA-approved in the U.S. (approved in some other countries).
Some clinics offer thymosin alpha-1 during cold season.
Wolverine stack
Slang for combining BPC-157 and TB-500, hoping to heal injuries faster. Both peptides are not FDA-approved.
He ran the Wolverine stack after a shoulder tear.
Hormones & Body
Peptides tied to growth hormone, desire, and body fat.
Sermorelin
A lab-made peptide designed to prompt the body to release its own growth hormone. Not an FDA-approved product today; sold through compounding pharmacies.
A clinic offered him sermorelin to nudge his own growth hormone; it is not FDA-approved today and comes from compounding pharmacies.
CJC-1295 & Ipamorelin
A popular research-stage pair studied for nudging growth hormone. Not approved medicines.
You will see CJC-1295 and Ipamorelin sold as a pair online, but they are research-stage and not approved medicines.
Tesamorelin
An FDA-approved medicine that reduces a specific kind of belly fat in people with HIV. Prescription only.
Tesamorelin (Egrifta) is a prescription medicine approved to trim a certain belly fat in people with HIV.
PT-141
An FDA-approved medicine for low sexual desire in women before menopause. Given as a shot before intimacy.
PT-141, sold as Vyleesi, is an FDA-approved shot for low sexual desire in some women before menopause.
HGH (human growth hormone)
A hormone the body makes to grow and repair itself. The lab-made version is called somatropin. It is FDA-approved for certain medical conditions, but sold illegally for anti-aging and bodybuilding.
The clinic prescribed HGH for a growth hormone deficiency.
IGF-1 (mecasermin)
A hormone that helps the body grow; the body makes it when growth hormone is working. The drug version, mecasermin, is FDA-approved for a rare growth disorder but sold illegally in fitness circles.
IGF-1 blood levels show whether growth hormone is doing its job.
MK-677 (Ibutamoren)
A pill that pushes the body to make more growth hormone. Popular in bodybuilding. Not FDA-approved for any use.
He tried MK-677 to sleep better and gain size.
Amylin (amylin analog)
A gut hormone that helps you feel full. Drug copies are called amylin analogs. One (pramlintide) is FDA-approved; newer ones are still being tested.
The newest shots add an amylin analog to curb hunger.
AOD-9604
A small piece of the growth hormone molecule once tested for fat loss. Not FDA-approved; it failed its main weight-loss trial.
AOD-9604 was hyped as a fat-burning peptide.
GHRP-2 / GHRP-6
Older peptides that signal the body to release growth hormone. GHRP-6 also causes strong hunger. Not FDA-approved.
GHRP-6 made him hungry within minutes.
Hexarelin
A strong peptide that signals the body to release growth hormone. Not FDA-approved.
Hexarelin is one of the more powerful growth-hormone peptides.
HCG (human chorionic gonadotropin)
A hormone drug used for fertility and to support men’s testosterone. FDA-approved for those uses; the “HCG diet” is not approved.
He added HCG to keep his testosterone from dropping.
Sleep, Energy & Focus
The ones studied for rest, energy, and the brain.
NAD+
Short for nicotinamide adenine dinucleotide, a helper molecule found in every cell that supports energy and repair.
People take NAD+ hoping for more energy; it is a helper molecule in every cell, sold as a supplement, not an approved drug.
MOTS-c
A tiny peptide made by your cells’ power plants (mitochondria), studied for energy and stamina. Not FDA-approved.
MOTS-c is made by the tiny power plants inside your cells and is studied for energy, but it is not FDA-approved.
Epitalon
A tiny peptide modeled on a substance from the pineal gland, the brain’s sleep-clock gland. Studied for sleep rhythm and aging. Not FDA-approved.
Epitalon is a research peptide studied for sleep and aging; it has not been approved as a medicine.
Semax
A brain-focused peptide used in Russia as a nasal spray, studied for focus and nerve health. Not approved by the FDA.
Semax is used in Russia as a nasal spray for focus, but the FDA has not approved it.
DSIP
The ‘deep sleep’ peptide. Sleep results have been mixed for 50 years, and FDA advisers voted against letting pharmacies make it. Not FDA-approved.
DSIP is nicknamed the deep-sleep peptide, but 50 years of results are mixed and it is not FDA-approved.
Selank
A Russian-made peptide people take for stress and focus, often as a nasal spray. It is a close cousin of Semax. Not FDA-approved in the U.S.
He uses Selank spray on stressful days.
SS-31 (Elamipretide)
A peptide that targets the tiny “batteries” inside cells (mitochondria). It is FDA-approved (as Forzinity, 2025) only for a rare disease called Barth syndrome; using it for energy or anti-aging is not approved.
People online talk about SS-31 for energy and aging.
5-Amino-1MQ
A research compound taken by mouth, promoted for fat loss and energy. Not FDA-approved; sold “research use only.”
5-Amino-1MQ is sold as a metabolism booster.
Vials & Doses
The hands-on words: vials, mixing water, syringes, and units.
Vial
The small glass bottle a peptide comes in, usually sealed with a rubber top.
The powder arrived in a tiny glass vial with a rubber cap.
Bacteriostatic water (BAC)
Sterile water with a tiny amount of benzyl alcohol (about 0.9%) added to stop bacteria from growing. In labs it is used to dissolve freeze-dried peptides, and a sealed vial can be used for about 28 days.
“Bacteriostatic water” is sterile water with a germ-stopping preservative added — a term you will see in lab and pharmacy settings.
Sterile water
Plain water with nothing living in it and no preservative added.
Sterile water has no preservative, so unlike BAC water it is not made for repeated use from the same vial.
Reconstitution
Mixing a freeze-dried powder with liquid so it turns back into a usable liquid.
Reconstitution just means adding liquid to a powder to dissolve it.
Lyophilized (freeze-dried)
Dried into a powder by freezing and vacuum. It is the form most peptides ship in because it lasts longer dry.
The peptide arrives lyophilized, which is a science word for freeze-dried into a powder.
Peptide calculator
An online tool some people mention for the math behind research peptides. It is not something peptides.io provides.
You will see “peptide calculator” mentioned in research-peptide forums; it is a tool peptides.io does not provide.
Concentration
How strong a mixed liquid is, meaning how much peptide sits in each drop of liquid.
Concentration means how much of something is packed into a liquid — a stronger mix has a higher concentration.
Subcutaneous injection
A shot given into the fat layer just under the skin, not into a muscle or a vein.
Most of these pens are a subcutaneous injection, so the needle goes into the fat just under the skin.
Intramuscular (IM) injection
A shot given deeper, into a muscle, instead of just under the skin.
An intramuscular shot goes into the muscle, deeper than a subcutaneous one under the skin.
Nasal spray
A spray sent into the nose instead of a shot. A few peptides, like Semax, are used this way.
Semax is often a nasal spray, meaning it is sprayed into the nose rather than injected.
Insulin syringe (U-100)
A small syringe marked in units, often used for under-the-skin shots. On a U-100 syringe, 100 units equals 1 milliliter.
A U-100 insulin syringe is the small, unit-marked syringe you will see used for shots like insulin and the weight-loss pens.
Units (on a syringe)
The little tick marks on a syringe used to measure a small amount of liquid.
The directions were in units, the tick marks printed along the side of the syringe.
Needle gauge
The thickness of a needle. A higher gauge number means a thinner needle.
A 31-gauge needle is thinner than a 27-gauge one, because a higher number means a finer needle.
IU (international unit)
A way of measuring some substances by their effect in the body rather than by their weight.
Some products are measured in IU, or international units, instead of milligrams.
Microgram (mcg) & milligram (mg)
The small weights peptides are measured in. One milligram equals one thousand micrograms.
A 5 mg vial holds 5,000 mcg, since one milligram is a thousand micrograms.
Drawing up
Pulling liquid from a vial into a syringe. “Draw” is the everyday word for it.
“Drawing up” is the everyday phrase nurses use for pulling liquid from a vial into a syringe.
Blend
A single vial that holds more than one peptide mixed together.
A blend is one vial holding two or more peptides at once, instead of just one.
Storage (cold chain)
Keeping peptides cold, in a fridge or freezer, so they do not break down. The dry powder is more stable than the mixed liquid.
You will see “store cold” on many medicine and lab labels — keeping something cold keeps it from breaking down.
Maintenance dose
The steady dose you stay on after slowly working up from a small starting dose.
It took two months to reach my maintenance dose.
Sharps container
A hard plastic bin for throwing away used needles safely, so no one gets poked.
A sharps container is the hard bin clinics use for used needles — you will see it named on medical supplies.
Injection site rotation
Changing the spot used for each shot, so the skin does not get sore or lumpy.
You will see “injection site rotation” in guides about the weight-loss pens — it means not using the same spot every time.
Injector pen
The ready-to-use device that holds the drug and gives a measured shot. The pen needle is the tiny tip that screws on.
The weight-loss shots come in an injector pen, the ready-to-use device that holds the medicine.
Sterile (aseptic) technique
Keeping everything germ-free during any mixing or injection, so nothing gets contaminated.
Sterile (aseptic) technique means keeping things germ-free — a basic rule in any clinic or lab.
Swirl, do not shake
The rule to gently roll a mixed vial instead of shaking it, because shaking can damage the peptide.
In lab and pharmacy notes you will see “swirl, do not shake” — shaking can damage a peptide.
Quality & Safety
How you’d tell if something is real, pure, and safe.
Certificate of Analysis (COA)
A lab report a seller shows to say what is inside a vial and how pure it is. It is only as trustworthy as the lab behind it.
A real COA, or Certificate of Analysis, is a lab report showing what is actually in the vial.
Purity
How much of what is in the vial is the actual peptide, versus leftover junk from making it.
A purity of 99% means almost all of the powder is the peptide, with very little else.
HPLC & mass spec
Two lab tests used to check a peptide’s identity and purity. HPLC sorts out what is in a sample; mass spec weighs the pieces to confirm what they are.
Labs use HPLC and mass spec to double-check that a peptide is really what the label claims.
Third-party tested
Checked by an outside lab, not just by the seller’s own word.
Third-party tested means an independent lab did the checking, not the company selling it.
Molecular weight
How heavy one molecule of a peptide is. Labs use it like a fingerprint to confirm they have the right peptide.
Each peptide has its own molecular weight, which labs use to confirm its identity.
Endotoxin
A poison left behind by bacteria. It can end up in a product made in dirty conditions and cause fever or worse.
Endotoxins are bacterial poisons that can be left behind when something is made in unclean conditions.
Research use only (RUO)
A label meaning something was sold for lab study, not as a medicine. It is still being tested — a heads-up, not a stamp of quality.
“Research use only” on a label means it was sold for lab study and is still being tested, not approved as a medicine.
Grey market / UGL
Sellers who operate outside normal medicine rules, including “underground labs” (UGLs). Quality and safety are not guaranteed.
A grey-market seller works outside the rules, so no one is checking that what is in the vial is safe.
Adverse event & MedWatch
A harmful reaction to a product. MedWatch is the FDA’s system for reporting one.
If a medicine causes a bad reaction, that is an adverse event, and you can report it to the FDA through MedWatch.
cGMP (Good Manufacturing Practice)
Strict cleanliness and quality rules that real drug makers must follow. Grey-market peptides skip these.
Pharmacy drugs are made under cGMP; most research peptides are not.
USP grade
A quality label meaning an ingredient meets official U.S. pharmacy standards for purity.
USP-grade is the pharmaceutical-quality standard you will see referenced.
Active pharmaceutical ingredient (API)
The actual drug substance inside a medicine, before it is mixed into a shot or a pill.
Compounders buy the semaglutide API as a bulk powder.
Rules & Labels
Words from labels and the law: approved, generic, compounded.
FDA approval
The FDA’s review of a drug’s safety and effectiveness before it can be sold for a given use.
FDA approval means the agency checked that a medicine is safe and works for a specific use before it can be sold.
Generic
A copy of a brand-name medicine that the FDA has also reviewed and approved. It must match the original’s active ingredient, strength, and form, and work the same way.
Once the patent ends, a cheaper generic can be sold — and the FDA checks that it works the same as the brand.
Compounded
A preparation mixed by a pharmacy. Compounded semaglutide is not FDA-approved and is not a generic of Wegovy® or Ozempic®.
The website sold compounded semaglutide, which is mixed by a pharmacy and is not the same as FDA-approved Wegovy.
503A pharmacy
A state-licensed pharmacy that compounds a medicine for one patient at a time, based on a prescription.
A 503A pharmacy mixes a medicine for one specific patient, based on their prescription.
503B outsourcing facility
A registered facility that can compound larger batches and must follow stricter FDA manufacturing rules.
A 503B outsourcing facility can make bigger batches and has to follow stricter FDA factory rules.
Boxed warning
The most serious safety warning the FDA can place on a drug label. It is set off inside a black box so it stands out.
The label carried a boxed warning, the strongest safety alert the FDA can require, printed inside a black box.
Clinical trial (RCT)
A study that tests a treatment in people. A randomized controlled trial, or RCT, compares it against a placebo or another option.
Before a drug is approved, it is tested in a clinical trial, where an RCT compares it fairly against a dummy pill.
Off-label
When a provider prescribes an approved drug for a use the FDA has not approved. The FDA has not reviewed that specific use.
When a doctor prescribes an approved drug for a use the FDA did not approve, that is called off-label.
Telehealth
Health care given at a distance, using video, phone, or secure messaging instead of an in-person visit.
She got her prescription through telehealth, meeting the clinician over video instead of driving to an office.
Supplement (DSHEA)
A product like a vitamin or a powder, sold as food. Under a 1994 law called DSHEA, the FDA does not approve supplements before sale.
Collagen is sold as a supplement, so under a 1994 law called DSHEA the FDA does not approve it before it hits shelves.
Research peptide
A peptide sold for lab study, not as a medicine, and still being tested. Quality and safety are not checked the way an approved medicine’s are.
“For research use only” on the label means it is sold for lab study, still being tested — not checked for safety the way real medicines are.
Compounded semaglutide / tirzepatide
A cheaper, pharmacy-mixed copy of these weight-loss drugs. It was widely sold during shortages, but after the shortages ended in 2025 the FDA stopped most legal compounding of them. Not FDA-approved.
I was buying compounded semaglutide online until the rules changed.
Prescription (Rx)
An order from a licensed provider that lets you legally get a specific drug.
You need an Rx to get real Wegovy from a pharmacy.
FAQ
Peptide questions, answered simply
What is a peptide, in simple terms?+
A peptide is a short chain of amino acids, the same building blocks that make up protein, just a smaller piece. Your body makes thousands of them to carry signals, like tiny messengers. Some peptides are FDA-approved medicines, some are in skincare and supplements, and many are still only research chemicals.
Are all peptides medicines?+
No. Peptides fall into very different groups: approved medicines a doctor can prescribe, everyday products like collagen powder and skin serums, and research-stage peptides that are not approved as medicines and still being studied. Knowing which group a peptide is in tells you how much to trust what you read about it.
What does “not FDA-approved” mean on a peptide?+
It means the FDA has not checked it for safety, how well it works, or quality for use as a medicine. It is a caution, not a loophole. Approved medicines have been tested in large studies; unapproved research peptides have not.
Are peptides safe?+
It depends on which peptide, and whether it is an approved medicine or an unregulated research product. Approved peptide medicines have known safety profiles when used under a doctor’s care. Research peptides sold online are not quality-checked, so what is actually in the vial is not guaranteed. Always talk to a licensed provider first.
How do I use this dictionary?+
Browse by category, or search any word you run into. Tap a term to see a simple definition and an example of how it is used. Keep it open in a tab while you read the rest of the site — whenever a word slows you down, look it up and keep going.
Why is peptide language so confusing?+
A lot of it comes straight from science and medicine, where one idea can have several names. Ads, labels, and social media then use those words with no explanation. This dictionary translates them into everyday words, so the jargon stops getting in your way.
Keep reading →
What Are Peptides? The five-minute answer, made simple
Now that the words make sense, meet the hormone behind the headlines — explained in the same everyday words.
Always talk to a licensed healthcare provider before starting any medicine. This page is for learning only — it is not medical advice.
Last updated: 2026-08-23 · Editorially reviewed by the Peptides.io team
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