503A pharmacy
A compounding pharmacy that prepares drugs for individual patients based on a specific prescription.
Under Section 503A of the Federal Food, Drug, and Cosmetic Act, a compounding pharmacy can prepare drugs tailored to an individual patient's prescription without needing FDA approval of the finished product. 503A pharmacies operate under state board oversight, not federal FDA oversight. They can compound drugs on the FDA's Category 1 bulk substances list or drugs in shortage.
Related: 503B pharmacy, FDA tracker
503B outsourcing facility
A larger-scale compounding facility that operates under FDA oversight and can compound without a patient-specific prescription.
Under Section 503B (added by the 2013 Drug Quality and Security Act), an outsourcing facility can compound sterile drugs in bulk for hospitals, clinics, and other providers — without a patient-specific prescription. 503B facilities must register with the FDA, follow cGMP, and undergo federal inspection. They can compound substances on the Category 1 bulk drug list.
Related: 503A pharmacy, FDA tracker
AEO
Answer Engine Optimization — structuring content to be cited by LLMs and AI search.
AEO is the 2024-onward evolution of SEO focused on large language models (ChatGPT, Claude, Perplexity) and Google's AI Overviews. Key techniques: FAQPage schema, MedicalWebPage schema, semantic-triple prose, dated citations, stable URLs, llms.txt, and machine-readable data endpoints. For a YMYL topic like peptides, authorial E-E-A-T signals matter disproportionately.
Amylin analog
A drug that mimics amylin, a hormone co-secreted with insulin that suppresses appetite.
Amylin is a peptide hormone released by pancreatic beta cells alongside insulin. Amylin analogs (cagrilintide, pramlintide) slow gastric emptying and promote satiety via the amylin receptor — a different pathway than GLP-1. When combined with a GLP-1 agonist (e.g., CagriSema = cagrilintide + semaglutide), the two mechanisms produce additive weight loss.
Related: CagriSema vs tirzepatide
Category 1 bulk drug substance
A bulk drug ingredient that 503A or 503B pharmacies may legally compound with.
The FDA maintains a list of 'bulk drug substances' that compounders may use even if the substance itself is not an FDA-approved drug. Category 1 substances are generally considered appropriate for compounding pending FDA's formal review. Substances in active shortage or on the FDA's approved list can generally be compounded.
Related: Category 2, FDA tracker
Category 2 bulk drug substance
A bulk drug ingredient the FDA has identified as potentially raising significant safety risks for compounding.
In 2023, the FDA placed 19 peptide substances on the Category 2 list, including BPC-157, CJC-1295, ipamorelin, GHK-Cu (injectable), Epitalon, MOTS-c, and others. Category 2 substances may not be compounded under 503A or 503B while they remain on the list. In February 2026, HHS proposed removing 14 of these from Category 2; FDA review and final determination is ongoing.
Related: Category 1, FDA tracker
COA (Certificate of Analysis)
A lab-issued document certifying the identity, purity, and content of a chemical product.
A Certificate of Analysis typically reports the results of HPLC, mass spectrometry, and endotoxin testing for a specific batch of a peptide. Reputable research peptide vendors publish batch-specific COAs from independent labs. Key fields: peptide identity, purity percentage (typically reported as ≥98% or ≥99%), batch/lot number, lab name, test date, and HPLC chromatogram.
Related: HPLC
Compounded semaglutide
Semaglutide prepared by a compounding pharmacy rather than Novo Nordisk's FDA-approved product.
During the 2022-2025 semaglutide shortage, 503A and 503B compounding pharmacies were permitted to prepare semaglutide for patients at costs well below the branded list price. The FDA declared the shortage resolved on February 21, 2025. 503A compounders lost discretion by April 22, 2025; 503B by May 22, 2025. Compounded semaglutide is no longer broadly legal for most patients as of April 2026.
Related: FDA tracker, Ozempic vs Wegovy
Dual agonist
A single drug molecule that activates two different receptors.
Tirzepatide is a dual GIP / GLP-1 receptor agonist — one molecule activates both receptors. This differs from CagriSema, which is a combination of two separate molecules (cagrilintide + semaglutide) co-administered in one injection. Dual and triple agonists (retatrutide is a triple GIP / GLP-1 / glucagon agonist) are an active area of obesity drug development.
Related: Tirzepatide, Retatrutide
E-E-A-T
Experience, Expertise, Authoritativeness, Trustworthiness — Google's quality signals for YMYL content.
Google's Quality Rater Guidelines lean heavily on E-E-A-T for Your Money or Your Life topics (medical, financial, legal). Signals include: named authors with verifiable credentials, medical reviewer attribution, primary-source citations, dated content, clear editorial standards, and transparent funding disclosures. Peptide content is textbook YMYL.
Related: YMYL, Editorial policy
FDA approval
Official FDA determination that a drug is safe and effective for a specific indication.
An FDA-approved drug has passed Phase 1, 2, and 3 clinical trials and had its application (NDA or BLA) reviewed by the agency. Approval is for a specific indication (e.g., 'chronic weight management in adults with BMI ≥30'), not for 'weight loss' in general. Off-label prescribing is legal but often not insurance-reimbursed. Compounded versions of approved drugs are not themselves FDA-approved.
Related: FDA tracker
GIP
Glucose-dependent insulinotropic polypeptide — an incretin hormone that stimulates insulin release.
GIP is one of two major incretin hormones released by the gut in response to food. Unlike GLP-1, GIP's role in weight regulation is complex and not fully understood, but drugs that agonize the GIP receptor (tirzepatide, retatrutide) produce larger weight loss than GLP-1-only agonists.
Related: GLP-1, Tirzepatide
GLP-1
Glucagon-like peptide-1 — an incretin hormone released by the gut that regulates blood sugar and appetite.
GLP-1 is released by intestinal L-cells after eating. It stimulates insulin release, suppresses glucagon, slows gastric emptying, and reduces appetite through central nervous system pathways. GLP-1 receptor agonists — including semaglutide, liraglutide, exenatide, and dulaglutide — mimic this hormone with longer half-lives.
Related: GLP-1 hub, Tirzepatide vs semaglutide
HPLC
High-performance liquid chromatography — the lab technique used to verify peptide purity.
HPLC separates the components of a peptide sample by polarity, allowing a lab to quantify how much of the sample is the target peptide versus impurities. Purity is reported as a percentage (≥98% is common for research-grade peptides). HPLC results are a key component of a Certificate of Analysis.
Related: COA
Incretin
A gut hormone that stimulates insulin release after eating.
The incretin family includes GLP-1 and GIP. Incretin-based therapies (GLP-1 agonists, DPP-4 inhibitors, dual/triple agonists) exploit this system to treat Type 2 diabetes and obesity. The 'incretin effect' explains why oral glucose provokes more insulin release than intravenous glucose at matched blood levels.
Off-label prescribing
A physician prescribing an FDA-approved drug for a use other than its approved indication.
Off-label prescribing is legal and common — estimated 20% of all US prescriptions. Insurance coverage, however, typically requires the prescription to match the approved indication. Ozempic prescribed for weight loss in a non-diabetic patient is a classic off-label example. Prescribers carry more liability for adverse outcomes with off-label use.
Related: Ozempic vs Wegovy
RUO (Research use only)
A labeling designation indicating a substance is sold for laboratory research and not for human consumption.
Research-use-only labeling is sometimes used by vendors selling unapproved peptides (BPC-157, TB-500, semax, etc.). The FDA has stated the RUO designation is void when the vendor also publishes dosing information, sells bacteriostatic water or syringes, or makes therapeutic claims. RUO is not a legal safe harbor if the totality of the marketing implies human use.
Related: FDA tracker
Schema.org markup
Structured data tags that help search engines and LLMs understand a page's content.
Schema.org is a collaborative vocabulary for structured data on the web, recognized by Google, Bing, and LLM crawlers. For peptide content, relevant types include Article, MedicalWebPage, FAQPage, Drug, Person (authors and reviewers), Organization, Dataset, and SpeakableSpecification. Proper schema improves AI Overview inclusion and LLM citation likelihood.
Related: AEO
STEP trials
Novo Nordisk's Phase 3 trial program for semaglutide in obesity.
The STEP trial series (STEP 1-8, 2021-2023) established semaglutide's efficacy and safety for chronic weight management at 2.4 mg weekly. STEP-1 (NEJM 2021) reported ~14.9% mean weight loss at 68 weeks. STEP-2 demonstrated efficacy in patients with T2D.
Related: Tirzepatide vs semaglutide
SURMOUNT trials
Eli Lilly's Phase 3 trial program for tirzepatide in obesity.
The SURMOUNT trial series (SURMOUNT-1 through SURMOUNT-5, 2022-2025) established tirzepatide's efficacy and safety for chronic weight management. SURMOUNT-1 (NEJM 2022) reported ~20.9% mean weight loss at 72 weeks on 15 mg. SURMOUNT-5 (NEJM 2025) was the first head-to-head vs semaglutide.
Related: Tirzepatide vs semaglutide, Zepbound vs Wegovy
Triple agonist
A single drug that activates three different receptors.
Retatrutide is a triple GIP / GLP-1 / glucagon receptor agonist. The addition of glucagon-receptor activity is theorized to contribute to further weight loss by increasing energy expenditure. Phase 2 results (NEJM 2023) reported 24.2% mean weight loss at 48 weeks on 12 mg; Phase 3 is ongoing as of April 2026.
Related: Retatrutide, Dual agonist
YMYL (Your Money or Your Life)
Google's classification for content that can materially affect readers' health, finances, or safety.
YMYL topics — medical, financial, legal, news — are held to higher quality standards by Google's algorithm and human raters. Peptide and drug content is unambiguously YMYL. Missteps include unsupported health claims, anonymous authorship, missing medical review, and thin affiliate content. Google's March 2024 Helpful Content Update and December 2025 core update both disproportionately hit thin YMYL content.
Related: E-E-A-T