# Peptide words, explained

The medical and legal words beginners meet, explained in plain English.

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Reading about peptides means meeting a lot of new words at once, some medical and some legal. This page explains the ones beginners run into most, in alphabetical order. Each entry has its own link, so you can point someone straight to it.

A definition here tells you what a word means. It does not tell you whether a product is right for you. For that, the [basics page](https://neopeptides.com/what-are-peptides/) is a good place to start, and a licensed clinician is the place to finish.

**503A pharmacy**: An ordinary pharmacy that makes a medicine to order for one named patient with a prescription. The name comes from section 503A of the U.S. drug law, which allows it.

**503B outsourcing facility**: A larger facility that makes batches of sterile medicines, often for clinics and hospitals. It must follow factory quality rules, and the FDA inspects it.

**Active ingredient**: The part of a medicine that does the work. Everything else in the vial or tablet is there to carry it or keep it stable.

**Adverse event**: Anything unwanted that happens to someone while taking a medicine. A report of one does not prove the medicine caused it.

**Advisory committee**: A panel of outside experts that advises the FDA in public meetings. Its vote is advice, not a decision, and it does not change the law on its own.

**Amino acid**: A small molecule that works as a building block. Link amino acids into a chain and you get a peptide or, if the chain is long enough, a protein.

**Bacteriostatic water**: Water with a preservative in it, used to mix a powdered medicine. When it is sold next to a peptide, the FDA treats that as a sign the peptide is meant to be injected.

**Biologic**: A medicine made from living cells rather than put together from chemicals. Some peptide medicines are legally biologics, and a pharmacy cannot compound a biologic at all.

**Bulk drug substance**: The raw active ingredient a pharmacy starts from, before it becomes a finished medicine. A pharmacy cannot compound with just any raw ingredient; the law sets tests it has to pass.

**Category 2**: The FDA's group of raw ingredients it has flagged as possible significant safety risks in compounding. The FDA says it may act against a pharmacy that uses one.

**Clinical trial**: A planned study in people that tests a medicine, usually by comparing a group who take it with a group who do not. The FDA relies on trials like these when it approves a medicine.

**Compounded medicine**: A medicine a pharmacy mixes or makes to order from a prescription, instead of a ready-made product from a drug company. It is not FDA-approved.

**Contraindication**: A reason a medicine should not be used by a particular person, such as a condition in their medical history. An approved medicine's label lists its contraindications.

**Controlled substance**: A drug the government tracks closely because it can be misused, with extra rules for prescribing it. Under federal law, most peptides and the GLP-1 medicines are not controlled substances.

**Drug shortage list**: A national list the FDA keeps of medicines that are officially in short supply. It is not the same as one local pharmacy being out of stock.

**Enforcement discretion**: The FDA saying what it does not plan to act against for now. It is not the same as something being legal.

**Essentially a copy**: A made-to-order version of a medicine you can already buy. The law limits when a pharmacy may make one, and a lower price is not a good enough reason.

**FDA**: The U.S. Food and Drug Administration, the federal agency that reviews medicines before they can be sold for a named use.

**FDA-approved**: The FDA has reviewed the evidence for one specific product and agreed that it works and is safe enough for a named use. Approval belongs to that product, not to every product with the same ingredient.

**FDA registered**: A business has listed itself with the FDA. It is not FDA approval, and implying that it is counts as misleading.

**GIP**: Short for glucose-dependent insulinotropic polypeptide, a hormone the gut releases after a meal. Tirzepatide acts on its receptor as well as the GLP-1 receptor.

**GLP-1**: Short for glucagon-like peptide-1, a hormone the gut releases after a meal that affects blood sugar and appetite. Medicines that copy it, such as semaglutide, are often called GLP-1 drugs.

**Hormone**: A chemical messenger that carries a signal from one part of the body to another. Many hormones, including insulin, are peptides.

**Injection pen**: A pen-shaped device that holds a medicine and uses a small needle to inject it under the skin. Many approved injectable medicines come in pens.

**Label**: The official information that comes with an approved medicine, also called prescribing information. It sets out what the medicine is approved for, its warnings and who should not use it. A compounded medicine may not come with the full version.

**LegitScript**: A private company that certifies health businesses against its own published standards, mostly so they can advertise online and take card payments. Its certification is not an FDA approval and does not rate the quality of care.

**MedWatch**: The FDA's free service for reporting a problem with a medicine. Patients can use it as well as clinicians.

**Multi-dose vial**: A small bottle holding more than one dose of a medicine. Its storage and disposal instructions depend on the specific product and its label.

**Nominated but withdrawn**: A table on the FDA's compounding safety page. On that page, current as of April 22, 2026, BPC-157, TB-500, injectable GHK-Cu and several other peptides sit here because the groups that asked the FDA to allow them took their requests back. It is not a clearance and not an approval, and the FDA's safety concerns are still printed beside each one.

**Peptide**: A short chain of amino acids. Insulin is one. The word alone says nothing about whether a product is safe, legal or meant for people.

**Placebo**: A dummy treatment with no active ingredient, given to one group in a clinical trial so researchers can compare it with the real medicine.

**Prescriber**: A clinician licensed to write prescriptions, such as a doctor. For telehealth, the prescriber has to be licensed in the state where you are.

**Prescription**: A licensed clinician's written order for a medicine for one named patient. Selling a prescription-only medicine without one is illegal.

**Promise Peptides**: Promise Peptides is a U.S. telehealth platform. Promise prescribes peptides now through licensed U.S. providers. A licensed U.S. provider reviews every request and your health history, then decides whether to prescribe. Not everyone qualifies, and the answer can be no. U.S. patients only. Availability varies by state and by treatment. Prescribed medicines are prepared by licensed U.S. compounding pharmacies. Each pharmacy separately decides whether it can lawfully prepare a prescription; a prescription does not guarantee it will be filled. Compounded medicines are not FDA-approved. Promise is LegitScript-certified. That certification is not FDA approval.

**Protein**: A long chain of amino acids, folded into a working shape. Peptides and proteins are made of the same building blocks; peptides are simply shorter.

**Receptor**: The docking point on a cell that a hormone or medicine fits into. When something binds to a receptor, the cell responds.

**Research use only**: A label some sellers put on vials. These products are sold for lab research, labelled not for human use, and no one reviews your health. The FDA has said the label does not change what a product legally is if it is really being sold for people.

**Side effect**: An unwanted effect of a medicine, alongside the effect it is meant to have. Approved labels list the ones seen in trials.

**State board of pharmacy**: The body in your state that licenses pharmacies. You can search its records to check the pharmacy named on a medicine label.

**State medical board**: The body in your state that licenses doctors and can discipline them. Its records of licences and public actions are open to anyone.

**Sterile**: Free of living germs. Anything injected has to be sterile, and there is a national standard for making medicines that way.

**Subcutaneous**: Under the skin. A subcutaneous injection goes into the layer of fat just beneath the skin, not into a muscle or vein.

**Telehealth**: Seeing a clinician by video, by phone or through an online form, instead of in the same room. The same standard of care applies either way.

**Unapproved new drug**: A drug without FDA approval. Selling it across state lines generally requires approval unless a legal exemption applies. Compounded medicines that meet all the requirements of section 503A or 503B can qualify for an exemption; that is not FDA approval.

**Vial**: A small glass bottle with a rubber top that holds a medicine, often as a liquid or a powder to be mixed.

## Sources

1. [Compounding and the FDA: Questions and Answers](https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers). U.S. Food and Drug Administration.
2. [Understanding the Risks of Compounded Drugs](https://www.fda.gov/drugs/human-drug-compounding/understanding-risks-compounded-drugs). U.S. Food and Drug Administration.
3. [Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act](https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act). U.S. Food and Drug Administration.
4. [Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks). U.S. Food and Drug Administration.
5. [21 U.S.C. 353b, Outsourcing facilities](https://www.law.cornell.edu/uscode/text/21/353b). Legal Information Institute, Cornell Law School.
6. [FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize](https://www.fda.gov/drugs/drug-alerts-and-statements/fda-clarifies-policies-compounders-national-glp-1-supply-begins-stabilize). U.S. Food and Drug Administration.
7. [FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss](https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss). U.S. Food and Drug Administration.
8. [21 U.S.C. 353, Exemptions and consideration for certain drugs, devices, and biological products](https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title21-section353&num=0&edition=prelim). Office of the Law Revision Counsel, U.S. House of Representatives.
9. [The Appropriate Use of Telemedicine Technologies in the Practice of Medicine](https://www.fsmb.org/siteassets/advocacy/policies/fsmb-workgroup-on-telemedicineapril-2022-final.pdf). Federation of State Medical Boards.
10. [Information For Consumers](https://www.fsmb.org/u.s.-medical-regulatory-trends-and-actions/guide-to-medical-regulation-in-the-united-states/information-for-consumers/). Federation of State Medical Boards.
11. [BeSafeRx: Locate a State-Licensed Online Pharmacy](https://www.fda.gov/drugs/besaferx-your-source-online-pharmacy-information/locate-state-licensed-online-pharmacy). U.S. Food and Drug Administration.
12. [Healthcare Certification: Operate Safely Online](https://www.legitscript.com/certification/healthcare-certification/). LegitScript.
13. [MedWatch: The FDA Safety Information and Adverse Event Reporting Program](https://www.fda.gov/safety/medwatch-fda-safety-information-and-adverse-event-reporting-program). U.S. Food and Drug Administration.
14. [FDA Adverse Event Monitoring System (AEMS) Public Dashboard](https://www.fda.gov/drugs/fda-adverse-event-monitoring-system-aems/fda-adverse-event-monitoring-system-aems-public-dashboard). U.S. Food and Drug Administration.
15. [USP General Chapter 797, Pharmaceutical Compounding: Sterile Preparations](https://doi.usp.org/USPNF/USPNF_M99925_07_01.html). United States Pharmacopeial Convention.

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A plain-English guide. Not a clinic, not a pharmacy, not a seller.

Neo points readers who want care to Promise Peptides. A licensed U.S. provider reviews each request and decides. Not everyone qualifies. U.S. patients only; availability varies by state and treatment. Compounded medicines are not FDA-approved. Neo may earn money when readers become Promise patients.

Neo is not affiliated with any company that has used the name Neo Peptides or NeoPeptides.