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D2C Peptides

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Peptide glossary

GLP-1 means glucagon-like peptide-1, a hormone released by the intestine.1 This glossary gives plain definitions of it and the other terms used on this site, from 503A bulks list to warning letter, each linked to the page that covers it.

This page summarizes published sources for information only. It is not medical advice and does not tell anyone to use a product. Questions about your own health belong with a licensed clinician. For questions about an order or a product, contact us.

Terms run A to Z. Each entry links to the page that covers it, and every health, legal or lab statement cites a source listed at the end of the page. Definitions report what sources say; none is advice on using a product.

#

503A bulks list
The list in federal regulations (21 CFR 216.23) of bulk drug substances that can be used to compound drugs under section 503A. As of October 25, 2026 it names six substances and no peptides.2 An FDA advisory committee met in July 2026 on adding seven peptides; its votes are non-binding.3 Read more: What are research peptides?.
503B outsourcing facility
A compounder registered with FDA under section 503B. FDA primarily oversees these facilities, and their drugs must meet current good manufacturing practice (CGMP) requirements, unlike drugs from pharmacies compounding under section 503A.4 As of April 2026, semaglutide and tirzepatide are not on FDA's 503B bulks list.5 Read more: What is GLP-1?.

A

Acromegaly
The disorder caused by too much growth hormone in adults, in more than 9 of 10 cases from a pituitary tumor, which is almost always benign. It enlarges the hands, feet and facial features and is linked to type 2 diabetes and heart disease. Excess GH in children before the growth plates close causes gigantism.6 Read more: What is HGH?.
Alcohol swab
A small pad wetted with 70% isopropyl alcohol, labeled as an antiseptic for external use only and not for the eyes.7 CDC vaccine guidance uses a sterile alcohol swab to clean the skin, which is then left to dry, and to wipe a vial's rubber stopper.8 Read more: Alcohol Swabs (Pack of 2) for sale.
Aliquot
A single-use portion split off from a larger amount, so the stock is not repeatedly thawed or opened.9 Peptide makers advise freezing aliquots of any peptide kept in solution, because freeze-thaw cycles can degrade peptides.910 Approved tesamorelin and somatropin labels say not to freeze the mixed solution.1112 Read more: How to store peptides.
Amino acid
The building block of peptides and proteins. NHGRI, part of the National Institutes of Health, says 20 different amino acids are used to build proteins.13 Some research peptides add unnatural ones: ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH2) has several, and FDA says they complicate its characterization.1415 Read more: What are peptides?.

B

Bacteriostatic water
Sterile water for injection with 0.9% or 1.1% benzyl alcohol as a preservative, in multiple-dose vials. Its label limits it to diluting or dissolving drugs for injection and says not to use it in newborns.16 FDA told one seller in 2026 that its bacteriostatic water, sold alongside peptides that need mixing, was itself a drug.17 Read more: Bacteriostatic Water for sale.
Benzyl alcohol
The preservative in bacteriostatic water. It slows bacterial growth so a vial can be entered more than once.16 Labels link it to serious and fatal reactions in newborns and infants, including 'gasping syndrome', and say not to use a benzyl alcohol diluent in anyone with a known hypersensitivity to it.12 Read more: How to reconstitute a peptide vial.
Beyond-use date
The date after which an opened or prepared product should not be used. CDC guidance, citing USP chapter 797, says an opened multiple-dose vial should be dated and thrown away within 28 days unless the manufacturer states another date, and that a beyond-use date should never pass the manufacturer's original expiration date.18 Read more: How to store peptides.
Biological product (biologic)
A medicine licensed through a biologics license application (BLA). On March 23, 2020, approved applications for biological products such as somatropin, mecasermin (Increlex) and tesamorelin (Egrifta) were deemed BLAs.19 Those transitioning biologics are not eligible for the compounding exemptions in sections 503A and 503B.20 Menopur (HMG) made the same switch.21 Read more: What is HGH?.
Bioregulator peptide
The name Vladimir Khavinson's group in St. Petersburg, Russia, gives very short peptides it links to particular organs, such as Cartalax (AED) with cartilage and Cardiogen (AEDR) with the cardiovascular system.22 Published Cardiogen work is cell, tissue and rat studies.2324 A 2026 review found independent Western validation lacking.25 Read more: What is Cardiogen?.
Boxed warning
A warning set in a box on a prescription drug label. On semaglutide and tirzepatide labels it covers thyroid C-cell tumors: both drugs caused them in rodents, and whether they do so in humans is not known.2627 Foundayo carries it too, though orforglipron is inactive in rodents and caused no tumors in them.28 Read more: GLP-1 side effects.

C

Category 2 (FDA compounding)
FDA's interim-policy category for bulk drug substances nominated for compounding that raise significant safety concerns.29 On FDA's 503A list dated May 14, 2026, Category 2 has six entries, and kisspeptin-10 is the only peptide among them.2915 BPC-157, TB-500, CJC-1295 and other peptides sat in Category 2 until their nominators withdrew them.15 Read more: What are research peptides?.
cc (cubic centimeter)
A unit of volume equal to 1 milliliter (mL); some syringes and vials say cc and others mL.30 On a U-100 insulin syringe, 1 mL spans 100 unit marks, so 0.5 cc is 50 units and 0.05 cc is 5 units.31 A 3 mL syringe is a 3 cc syringe. Read more: Peptide units converter.
Certificate of analysis (COA)
A test report for one batch, or lot, of a substance. FDA's Q7 guidance says it should list each test with its acceptance limits and numerical results, be dated and signed by the quality unit, and name the original manufacturer.32 Check that its lot number matches the vial. Read more: Lab results and certificates of analysis.
Compounded drug
A drug mixed by a pharmacy or an outsourcing facility rather than made under an FDA approval. FDA does not review compounded drugs for safety, effectiveness or quality before they are sold.33 When a shortage ends, section 503A restricts compounding of drugs that are essentially copies of the commercially available one.5 Read more: What is GLP-1?.
Concentration
How much compound each milliliter of liquid holds after mixing: the amount in the vial divided by the volume of diluent added. For example, 5 mg in 2 mL gives 2.5 mg/mL. On a U-100 syringe each unit is 0.01 mL, so at 2.5 mg/mL one unit holds 0.025 mg. Read more: Reconstitution calculator.
Counter ion
An ion paired with a synthetic peptide in its salt form. EMA says synthetic peptides usually come with acetate, though trifluoroacetate (TFA) or chloride are possible.34 The salt can matter legally: FDA says semaglutide sodium and semaglutide acetate are different active ingredients from the one in approved semaglutide drugs.33 Read more: What are research peptides?.

D

DAC (drug affinity complex)
A chemical add-on in CJC-1295 with DAC that lets the peptide bind albumin in the blood.36 In healthy adults, its estimated half-life was 5.8 to 8.1 days, and one injection raised average growth hormone 2- to 10-fold, depending on dose, for 6 days or more.35 CJC-1295 without DAC has no controlled human studies.36 Read more: What is CJC-1295 with DAC?.
Diluent
The liquid used to dissolve or dilute a drug before injection, such as Sterile Water for Injection or Bacteriostatic Water for Injection.1637 Approved products name their own: EGRIFTA SV uses 0.5 mL of sterile water, EGRIFTA WR 1.3 mL of bacteriostatic water, and both labels allow only the supplied diluent.1138 Read more: How to reconstitute a peptide vial.
Dose escalation (titration)
Starting a medicine at a low dose and raising it in steps over weeks. Ozempic's label does this to lower the risk of stomach and gut side effects: 0.25 mg once weekly for 4 weeks, then 0.5 mg.26 The prescriber sets each step; research-grade vials are unapproved and have no label dose.33 Read more: GLP-1 dosage.

E

Endotoxin
A toxin held in the cell wall of certain microorganisms and released when the cells break apart.39 Standards recommend testing finished products for it; FDA has accepted the LAL (Limulus amoebocyte lysate) test for over 30 years.40 A 2024 study found endotoxin in all 3 semaglutide vials obtained from illegal online pharmacies.41 Read more: Lab results and certificates of analysis.

F

Falsified and substandard products
WHO calls a medical product substandard when it fails quality standards, often through poor manufacturing, and falsified when it deliberately misrepresents its identity, composition or source. Both are often sold online.42 A 2018 Belgian study of falsified peptide drugs found purity of 5% to 75% for cysteine-containing peptides, plus arsenic and lead.43 Read more: Peptide safety basics.

G

Gauge (needle)
The number that gives a needle's thickness: the higher the gauge, the thinner the needle, so an 18G needle is wider than a 25G one.44 Needles on U-100 insulin syringes can be as thin as 31 gauge and as short as 6 mm.44 Length is listed separately. Read more: Peptide supplies explained.
Ghrelin
A 28-amino-acid hormone first found in rat stomach in 1999. It switches on the growth hormone secretagogue receptor to release GH, and works only with a fatty acid group at position 3.45 It also drives hunger: in 9 healthy volunteers, a ghrelin infusion raised energy eaten at a buffet by 28% versus saline.46 Read more: What is GHRP-6?.
GHRH (growth hormone-releasing hormone)
A hormone from the hypothalamus that signals the pituitary gland to make and release growth hormone in pulses.4748 Sermorelin, tesamorelin and CJC-1295 are GHRH analogs.36 Tesamorelin is FDA approved to reduce excess abdominal fat in adults with HIV and lipodystrophy; sermorelin, sold as GEREF, was discontinued in 2008.4849 Read more: What is Sermorelin?.
GHRP (growth hormone-releasing peptide)
A small synthetic peptide, such as GHRP-2 or GHRP-6, that makes the pituitary release growth hormone through the ghrelin receptor.36 In 18 healthy men, single intravenous doses of the original GHRP gave average GH peaks up to 68.7 micrograms per liter, against 1.2 on placebo.50 FDA lists GHRP-2 and GHRP-6 as possible significant safety risks in 503B compounding.15 Read more: What is GHRP-2?.
GHS-R (ghrelin receptor)
The growth hormone secretagogue receptor, found in the pituitary and hypothalamus and cloned in 1996. Ghrelin and synthetic secretagogues act through it to trigger and amplify pulses of growth hormone release.5145 Ipamorelin, GHRP-2 and GHRP-6 target this receptor, not the GHRH receptor.36 Read more: What is Ipamorelin?.
GIP (glucose-dependent insulinotropic polypeptide)
A second gut hormone. Tirzepatide's label describes the drug as an agonist at both the GIP and GLP-1 receptors.27 Retatrutide adds a third target, the glucagon receptor, so researchers call it a triple agonist.52 FDA says retatrutide is in no approved drug and has not been found safe and effective.33 Read more: What is Tirzepatide?.
GLP-1 (glucagon-like peptide-1)
GLP-1 means glucagon-like peptide-1, a natural hormone released by the intestine.1 It helps lower blood sugar after eating and acts in brain areas that control appetite and food intake.1 In drug names, 'GLP-1' points to medicines that mimic this hormone; FDA approved the first, Byetta (exenatide), in 2005 for type 2 diabetes.53 Read more: What is GLP-1?.
GLP-1 receptor agonist (GLP-1 RA)
A drug that mimics GLP-1 by switching on its receptor. FDA describes three effects: more insulin release, lower blood sugar after meals, and slower movement of food through the gut, which can help a person feel full longer. Semaglutide, liraglutide, dulaglutide and exenatide are examples.53 On Ozempic's label, stomach and gut effects are the most common side effects.26 Read more: What is Semaglutide?.
GnRH (gonadotropin-releasing hormone)
The 10-amino-acid hypothalamic hormone that signals the pituitary to release LH and FSH; gonadorelin is its lab-made form.5455 Its short half-life means clinical use needs infusion pumps, and continuous exposure desensitizes the pituitary cells it acts on.5554 Kisspeptin acts upstream, signaling directly to GnRH neurons.56 Read more: What is Gonadorelin?.
Gonadotropin
A hormone that acts on the ovaries or testes. HMG (menotropins) supplies two, FSH and LH, the signals that grow and mature egg follicles.57 hCG, made by the placenta, acts almost exactly like the pituitary's LH and has a little FSH activity, prompting the testes to make androgens.5859 Read more: What is HCG?.
Growth hormone (GH, somatropin)
A 191-amino-acid protein hormone, made mainly by the pituitary gland, that controls body growth.660 Somatropin is the drug form, made with recombinant DNA and identical in sequence to the natural hormone.60 Federal law makes distributing it for human use other than physician-ordered, FDA-authorized treatment a crime.61 Read more: What is HGH?.
Growth hormone secretagogue (GHS)
A substance that makes the body release more of its own growth hormone. The term often means ghrelin-receptor agonists such as GHRP-2, GHRP-6 and ipamorelin;5136 some reviews also count GHRH analogs such as CJC-1295 and tesamorelin.62 A 2026 sports medicine review called these secretagogues investigational, with uncertain safety and product quality concerns.62 Read more: What is CJC-1295 + Ipamorelin?.

H

Half-life
The time a substance takes to lose half of its pharmacologic, physiologic or radiologic activity.63 Peptides tend to have short ones:64 tesamorelin's elimination half-life is 11 minutes and ipamorelin's terminal half-life about 2 hours.4865 Others last far longer: semaglutide's half-life is about one week.66 Read more: What are peptides?.
HPLC (high-performance liquid chromatography)
A liquid chromatography method using high inlet pressure for high sensitivity and speed.67 Bachem, a peptide maker, says research peptides are typically more than 95% pure by HPLC. High HPLC purity does not mean the powder is all peptide (see net peptide content).68 Read more: Lab results and certificates of analysis.
Hygroscopic
Tending to pull water out of the air. Peptides tend to be hygroscopic, and absorbed moisture lowers a powder's peptide content and may lower its stability.10 Peptide makers advise letting a cold vial reach room temperature in a desiccator, a sealed container kept dry with a drying agent, before opening it.109 Read more: How to store peptides.

I

IGF-1 (insulin-like growth factor 1)
A hormone the liver makes in response to growth hormone; it carries out much of GH's growth effect.6 Because GH swings through the day while IGF-1 stays steadier, an IGF-1 blood test is a reliable way to track GH activity.69 IGF-1 LR3 is an engineered analog with no peer-reviewed human studies.36 Read more: What is IGF-1?.
Impurity
Any component of a substance that is not the intended substance.32 Under the European Pharmacopoeia thresholds cited by EMA, peptide-related impurities in a peptide medicine should be reported above 0.1%, identified above 0.5% and qualified above 1.0%.34 EMA's tests also cover residual solvents and elemental impurities.34 Read more: Lab results and certificates of analysis.
In vitro
Done in a test tube, dish or cell culture, not in a living animal or person. Federal rules let a new drug meant only for in vitro tests or lab animal research be shipped if labeled 'Not for use in humans'.70 On this site, 'in cell studies' marks in vitro evidence. Read more: What are research peptides?.
Insulin syringe
A small disposable syringe with the needle attached, marked in units instead of milliliters.4466 Most are made for U-100 insulin, and every small notch on a standard 1 mL syringe is 1 unit.31 MedlinePlus says never to reuse needles or syringes, and the American Diabetes Association says never to share one.3171 Read more: Insulin Syringes (Pack of 10) for sale.
International unit (IU)
A unit used for some hormones in place of weight. The WHO International Standard for somatropin assigns 3.0 IU per mg and calls IU a historical unit that mass can be converted to.72 An EU label puts 10 IU at 3.3 mg of somatropin.73 Menopur vials hold 75 IU of FSH and 75 IU of LH.21 Read more: Peptide dosage basics.
Investigational New Drug application (IND)
The FDA filing through which a study sponsor gets an exemption from the rule that a drug needs an approved marketing application before it is shipped across state lines. Sponsors need it to ship an unapproved drug to clinical investigators for studies in people.74 Read more: What are research peptides?.

L

Luer-Lok tip (Luer lock)
A threaded syringe tip that a separate needle screws onto and locks in place.7576 Luer connectors join a male and a female part into a secure, detachable, leak-proof connection, either by pushing them together (a Luer slip) or with a screw-in thread (a Luer lock).76 Read more: 3mL Syringe, Luer-Lok Tip for sale.
Lyophilized (freeze-dried)
Dried by freezing, then removing the water under vacuum so the ice turns straight into vapor. FDA lists the dry powder's better stability as an advantage and the need for a sterile diluent as a drawback.77 Peptide makers advise long-term freezer storage: below -15 °C (Bachem) or at -20 °C (GenScript).109 Read more: How to store peptides.

M

Mass spectrometry (MS)
A lab method that identifies a chemical by its mass.78 For peptides, EMA says it can determine the molecular mass and confirm the amino acid sequence, so it is used to check identity.34 It can be paired with liquid chromatography, as in a 2024 study that measured semaglutide in vials sold online.41 Read more: Lab results and certificates of analysis.
Medullary thyroid carcinoma (MTC)
A cancer of the thyroid's C-cells.26 GLP-1 labels say not to use these drugs with a personal or family history of MTC or with MEN 2 (multiple endocrine neoplasia type 2).2628 Patients are told to report a neck lump, trouble swallowing, shortness of breath or lasting hoarseness.28 Read more: GLP-1 side effects.
Melanocortin receptor
One of five receptors, MC1R to MC5R, that alpha-melanocyte-stimulating hormone and peptides modeled on it act on. Bremelanotide (PT-141) activates several of them nonselectively, MC1R and MC4R most potently.79 Melanotan 2, also nonselective, caused mild nausea and a stretching and yawning complex linked to spontaneous erections in a 1996 pilot study of 3 men.8081 Read more: What is PT-141?.
Misbranded drug
A drug whose labeling or sale breaks FD&C Act rules. FDA says a drug is misbranded if its labeling lacks adequate directions for use, meaning directions a layperson can follow safely, and that such directions cannot be written for prescription drugs. Selling a prescription drug without requiring a prescription also misbrands it.82 Read more: What are research peptides?.
Mitochondrial-derived peptide
A peptide encoded in mitochondrial DNA. MOTS-c is one: a 16-amino-acid peptide encoded by a short open reading frame in the mitochondrial 12S rRNA gene, first described in 2015.83 FDA says it has not identified any human exposure data on drug products containing MOTS-c.15 Read more: What is MOTS-c?.
Molecular weight (molar mass)
The sum of the weights of all the atoms in a molecule.84 Therapeutic peptides usually weigh about 500 to 5,000 daltons.64 Somatropin, a 191-amino-acid protein, weighs 22,124 daltons.60 Product pages list it as molar mass in grams per mole, alongside the molecular formula. Read more: Peptides A to Z.
Multiple-dose vial
A vial that contains a preservative and is meant to be entered more than once, such as bacteriostatic water.16 MedlinePlus advises writing the date on such a vial when it is first opened.30 FDA reports linked overdoses to drawing doses from multiple-dose vials of compounded semaglutide.66 Read more: How to store peptides.

N

Net peptide content
The share of a peptide powder's weight that is actually peptide; the rest is counter ions, such as acetate or trifluoroacetate, and residual water. Bachem, a peptide maker, gives a typical range of 70 to 90% and says to account for it when making a solution of a set concentration.68 Read more: Peptide calculator.

P

Peptide
A short chain of amino acids, typically 2 to 50, joined by peptide bonds; the chain can be linear, branched or cyclic.8586 MeSH calls chains of about 2 to 12 amino acids oligopeptides.86 A 2022 review counts more than 80 approved peptide drugs worldwide, the first being insulin in 1921.64 Read more: What are peptides?.
Peptide blend (stack)
A product that combines two or more peptides in one vial, such as BPC-157 with TB-500. FDA named two blends of tesamorelin and ipamorelin as unapproved new drugs in August 2026 warning letters.8788 For approved prescription drugs, FDA allows fixed combinations only when each component contributes to the claimed effects.89 Read more: Peptide blends and stacks.
Polypeptide
A longer chain of amino acids. The cutoff depends on the source: NHGRI uses 51 or more amino acids, while NLM's MeSH vocabulary uses about 13 or more.8586 Proteins are built from one or more polypeptides, with the order of amino acids in each chain encoded in a gene.13 Read more: What are peptides?.
Protein
A molecule made of one or more polypeptide chains.13 In US drug rules, a protein is any alpha amino acid polymer with a specific, defined sequence longer than 40 amino acids.90 By that line, tesamorelin (44 amino acids) and somatropin (191) are proteins, and both are licensed as biologics.486019 Read more: What are peptides?.
Pulmonary aspiration
Stomach contents getting into the lungs. The Ozempic label notes that the drug delays stomach emptying and reports rare cases during general anesthesia or deep sedation, even in people who followed fasting rules.26 It tells patients to inform their providers of any planned surgery or procedure.26 Read more: GLP-1 side effects.
Purity
How free a sample is of impurities. EMA lists total and individual impurities among the tests in a peptide's specification.34 A label figure can be wrong: in a 2024 study, 3 semaglutide vials sold online without a prescription measured 7.7% to 14.37% pure, against the 99% printed on their labels.41 Read more: Lab results and certificates of analysis.

R

Reconstitution
Dissolving a freeze-dried powder in a sterile liquid, the diluent, before use.77 Approved labels describe the technique: run the diluent down the inside wall of the vial to avoid foaming, then swirl or roll gently. They say not to shake, because shaking can make the solution cloudy.1211 Read more: How to reconstitute a peptide vial.
Research use only (RUO)
In FDA rules, 'For Research Use Only' labels lab tests still in research; an unapproved drug shipped for lab or animal research must instead say 'Not for use in humans'.9170 FDA judges intended use from labeling, advertising and how a product is sold, and in 2026 warning letters it found sellers' research-labeled peptides were drugs meant for people.92178893 Read more: Research use policy.

S

Sequence (amino acid sequence)
The order of amino acids in a peptide chain, also called its primary structure.94 It is written in three-letter or one-letter codes: TB-500 is Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH, or LKKTETQ with an acetyl group in front.95 Mass spectrometry can confirm a sequence.34 Product pages list it in the specification table. Read more: Peptides A to Z.
Sharps
FDA's term for devices with sharp points or edges that can puncture or cut skin: needles, syringes, lancets, auto-injectors such as insulin and epinephrine pens, infusion sets and connection needles.96 Sharps that are not disposed of safely can injure people and spread infections, most commonly hepatitis B, hepatitis C and HIV.96 Read more: How subcutaneous injections are given.
Sharps disposal container
A rigid, puncture-resistant container with a tight lid and a fill line for used needles.97 FDA advises putting sharps in one right after use and following local disposal rules when it is about three-quarters full.98 Without one, a heavy-duty plastic household bottle with a tight, puncture-resistant lid can serve, labeled as hazardous waste.9697 Read more: How subcutaneous injections are given.
Single-dose vial
A vial, usually without a preservative, meant for one use;18 Sterile Water for Injection comes only in single-dose containers.37 CDC guidance says leftover contents should not be pooled or stored for later use.18 So tesamorelin mixed with sterile water (EGRIFTA SV) is injected right away and the rest discarded.11 Read more: How to store peptides.
Somatostatin
A hypothalamic hormone that holds back growth hormone release. Human studies with frequent blood sampling suggest GH bursts occur when somatostatin tone drops, so GH comes in pulses.47 In 6 healthy men, a 48-hour IGF-1 infusion cut GH by 85%, which the authors linked to somatostatin.99 Read more: What is HGH?.
Sterile Water for Injection
Sterile water with no preservative, antimicrobial agent or added buffer, supplied only in single-dose containers.37 Its label limits it to diluting or dissolving drugs for injection and warns that giving it into a vein on its own may burst red blood cells (hemolysis).37 Labels name it for preparing medicines for newborns.16 Read more: How to reconstitute a peptide vial.
Subcutaneous injection (SQ, sub-Q)
An injection into the fatty tissue just under the skin.100 MedlinePlus lists insulin, blood thinners and fertility drugs among medicines people give themselves this way, and names the belly, the outer upper thighs and the back or side of the upper arms as the best areas.100 Read more: How subcutaneous injections are given.

T

Thymosin beta-4
A natural 43-amino-acid protein. TB-500 is a synthetic 7-amino-acid piece of it, positions 17 to 23 (LKKTETQ), which includes the protein's actin-binding region.95 FDA says it has not identified any human exposure data for TB-500, and WADA bans thymosin beta-4 derivatives such as TB-500 at all times.15101 Read more: What is TB-500?.

U

U-100
A concentration label for insulin meaning 100 units in each milliliter, the most common insulin strength.31102 Most insulin syringes are marked for it, so each unit line is 0.01 mL.31 To turn a volume into U-100 units, multiply mL by 100: 0.2 mL is 20 units. Read more: Peptide units converter.
Unapproved new drug
A new drug sold without the FDA-approved application federal law requires before it is shipped across state lines.74 In an August 2026 warning letter, FDA called one seller's research-labeled semaglutide, tirzepatide, retatrutide, SS-31, tesamorelin and PT-141, and its bacteriostatic water, unapproved new drugs.93 Read more: What are research peptides?.
Unit (syringe marking)
A volume mark on an insulin syringe, not a weight: on a U-100 syringe 1 unit is 0.01 mL.31 How many milligrams a unit holds depends on the liquid's concentration. FDA says confusing units with milliliters or milligrams may have contributed to compounded semaglutide errors in which patients took 5 to 20 times the intended dose.66 Read more: Peptide dosage basics.

W

WADA class S0
The non-approved substances class of the World Anti-Doping Agency's Prohibited List, banned at all times; the 2026 list names BPC-157 in it.101 The 2027 list, in force from January 1, 2027, adds 'peptides' to the class's examples.103 USADA says no health authority anywhere has approved BPC-157 for human clinical use.104 Read more: What is BPC-157?.
WADA class S2
The Prohibited List class for peptide hormones, growth factors and related substances, banned at all times. The 2026 list names CJC-1295, sermorelin, tesamorelin, ipamorelin, GHRP-2 and GHRP-6; GH fragments such as AOD-9604; growth factors including MGFs and TB-500; and, for males, gonadorelin and kisspeptin.101 Read more: What is CJC-1295 with DAC?.
WADA Prohibited List
The World Anti-Doping Agency's list of substances and methods banned in sport; the 2026 list took effect January 1, 2026 and the 2027 list takes effect January 1, 2027.101103 GLP-1 drugs such as semaglutide and tirzepatide are not on it, and WADA kept their status unchanged for 2027.105 Read more: What are research peptides?.
Warning letter
FDA's usual notice to a company when it believes there are significant violations of federal requirements; it names the concerns and asks for a response within a set time.106 Letters to peptide sellers in 2024 to 2026 asked for a written reply within 15 working or business days and warned of possible seizure and injunction.107108 Read more: What are research peptides?.

Evidence words used on this site

Health statements on this site name the kind of evidence behind them.

  • Label fact: what an FDA-approved label states, true for that product only.
  • In cell studies: lab work on cells or tissue (in vitro).
  • In rats or mice: animal studies, not tests in people.
  • Case report: what happened to one person, with no comparison group.
  • Randomized trial: people assigned by chance to the compound or a placebo.
  • Systematic review: a structured search and appraisal of all studies on one question; a meta-analysis pools their data, as FDA's analysis of 91 placebo-controlled GLP-1 drug trials did.1

Written by D2C Peptides Editorial Team.

Pending qualified review.

Updated .

Sources

  1. FDA Requests Removal of Suicidal Behavior and Ideation Warning from Glucagon-Like Peptide-1 Receptor Agonist (GLP-1 RA) Medications (Drug Safety Communication, 01-13-2026). U.S. Food and Drug Administration, 2026.
  2. 21 CFR 216.23 Bulk drug substances that can be used to compound drug products in accordance with section 503A of the FD&C Act. Electronic Code of Federal Regulations (eCFR), 2026.
  3. July 23-24, 2026: Meeting of the Pharmacy Compounding Advisory Committee. US Food and Drug Administration, 2026.
  4. Compounding and the FDA: Questions and Answers. US Food and Drug Administration, 2026.
  5. FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize. US Food and Drug Administration, 2026.
  6. Acromegaly. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK, NIH), 2020.
  7. ISOPROPYL ALCOHOL swab (BD Alcohol Swabs) label. U.S. National Library of Medicine, DailyMed (labeler: Becton Dickinson and Company), 2024.
  8. Chapter 6: Vaccine Administration (Pink Book). U.S. Centers for Disease Control and Prevention.
  9. Peptide Storage and Handling Guidelines. GenScript.
  10. Handling and Storage Guidelines for Peptides (Peptide Guide, chapter 8). Bachem.
  11. EGRIFTA SV (tesamorelin for injection) prescribing information and instructions for use. U.S. Food and Drug Administration (Drugs@FDA label), 2024.
  12. ZOMACTON (somatropin) for injection, prescribing information (revised 7/2025). DailyMed, U.S. National Library of Medicine, 2025.
  13. Amino Acids (Talking Glossary of Genomic and Genetic Terms). National Human Genome Research Institute (NIH), 2026.
  14. Ipamorelin, the first selective growth hormone secretagogue (Raun et al.). European Journal of Endocrinology (PubMed abstract), 1998.
  15. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. US Food and Drug Administration, 2026.
  16. Bacteriostatic Water for Injection, USP (multiple-dose vial) prescribing information. Hospira, Inc. (Pfizer labeling), 2019.
  17. Warning Letter: Gram Peptides, MARCS-CMS 721806 (March 31, 2026). US Food and Drug Administration, CDER, 2026.
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