The GLP-1 market glossary: every term this site uses, defined honestly

This market runs on borrowed vocabulary — pharmacy law, trial acronyms, pricing jargon — and half its marketing works by using these words decoratively. Here is each one defined the checkable way, with links into the guides that go deep. Legitimate sellers use these terms precisely because each is verifiable; keep the list handy and product pages start sorting themselves.

503A pharmacy. A state-licensed pharmacy compounding patient-specific prescriptions — the only lawful lane for compounded tirzepatide in 2026. Deep dive →

503B outsourcing facility. FDA-registered bulk compounder; the pathway that supplied mass-market GLP-1 copies until it closed for tirzepatide in March 2025. Deep dive →

AHI (apnea-hypopnea index). Breathing interruptions per hour of sleep — the number that defines sleep-apnea severity and that tirzepatide cut ~55–60% in SURMOUNT-OSA. Deep dive →

API (active pharmaceutical ingredient). The raw drug substance a pharmacy compounds from; its FDA-registered sourcing is a fair question to ask any program.

Base form (free base). The unmodified tirzepatide molecule used in approved products — the only lawful compounding input, versus never-tested salt forms. Deep dive →

Beyond-use date (BUD). The compounded world's expiration date, set from the pharmacy's stability data and always shorter than brand dating. A vial without one cannot be dosed from. Deep dive →

Boxed warning. The FDA's strongest label warning; for tirzepatide it covers thyroid C-cell tumors seen in rodents, driving the MTC/MEN2 contraindication. Deep dive →

Certificate of analysis (COA). Lab documentation of a lot's identity and purity. Necessary — and routinely misused as if it proved absorption or FDA approval. Deep dive →

Compounded medication. A drug prepared for a specific patient by a licensed pharmacy rather than manufactured under an FDA approval; same molecule, different oversight. Deep dive →

Dose-based pricing. Program structure where the monthly price rises with your dose — cheapest during initiation, most expensive exactly at maintenance. Deep dive →

Flat-rate pricing. One price across all doses — the structure NexLife claims ('Flat Forever') and the field our dataset scores, because it changes titration economics.

Foundayo (orforglipron). Lilly's non-peptide daily GLP-1 pill, approved April 1, 2026 — the first with no food or water restrictions; $149–349/month self-pay. Deep dive →

GIP. Glucose-dependent insulinotropic polypeptide — the second receptor tirzepatide activates, plausibly behind its efficacy edge over GLP-1-only drugs. Deep dive →

GLP-1 receptor agonist. Drug class impersonating the incretin hormone GLP-1: slows gastric emptying, quiets appetite, improves insulin response.

Incretin. Gut hormones (GLP-1, GIP) released after eating that regulate insulin and appetite — the system this entire drug class borrows.

KwikPen. Lilly's prefilled multi-dose pen; the only Zepbound formulation the Medicare GLP-1 Bridge covers (vials are excluded). Deep dive →

LillyDirect. Eli Lilly's direct-to-patient channel; Zepbound vials $299–449/month after the December 2025 cut, Foundayo from $149.

Maintenance dose. The tolerated, effective dose you stay on after titration — 5–15 mg for tirzepatide; the price at this dose, not month one's, is your real cost. Deep dive →

Medicare GLP-1 Bridge. CMS demonstration (Jul 1, 2026 – Dec 31, 2027): $50/month for Wegovy, Zepbound KwikPen, and Foundayo for eligible Part D beneficiaries. Deep dive →

Microdosing. Marketing term spanning slow titration (legitimate), minimum-effective dosing (legitimate), and sub-2.5 mg protocols (unstudied). Deep dive →

MTC / MEN2. Medullary thyroid carcinoma and Multiple Endocrine Neoplasia type 2 — personal or family history of either is the boxed-warning contraindication.

ODT (orally disintegrating tablet). Dissolve-in-mouth format. No compounded tirzepatide ODT has published human absorption data; priced $199–229 in operator listings anyway. Deep dive →

Patient-specific compounding. The 2026 legal basis: a prescription for a named patient with a documented clinical reason the approved product doesn't fit. Deep dive →

Prior authorization (PA). Insurer pre-approval; where brand GLP-1 coverage is won or lost, and the mechanism the Bridge and OSA pathways run through.

Retatrutide. Lilly's triple agonist (GLP-1/GIP/glucagon): 24.2% average loss in phase 2 at 48 weeks, in phase 3 now — zero legal ways to buy it. Deep dive →

Rybelsus. Oral semaglutide for type 2 diabetes — the SNAC-carried peptide pill whose ~1% bioavailability defines why peptide tablets are hard.

Salt form (e.g., tirzepatide sodium). Chemically modified variants never tested in humans and outside the lawful compounding lane — an FDA warning-letter staple. Deep dive →

SNAC. The absorption-enhancer technology that makes oral semaglutide possible at ~1% bioavailability — and imposes its fasting rules. Deep dive →

SURMOUNT. Tirzepatide's obesity trial program: SURMOUNT-1 (15–20.9% by dose), -4 (withdrawal/regain), -5 (head-to-head vs semaglutide), -OSA (sleep apnea).

Telogen effluvium. Synchronized hair shedding 2–4 months after a body shock like rapid weight loss — the real mechanism behind 'GLP-1 hair loss.' Deep dive →

Titration. The scheduled dose ladder (2.5→15 mg at 4-week minimums) that builds GI tolerance; every interval is a minimum, not an appointment. Deep dive →

True monthly cost. Our computed all-in figure: advertised price + membership + shipping + amortized consultation — the number comparisons should use.

Units (insulin syringe). Volume marks, not dose: 100 units = 1 mL. Your mg dose depends on the vial's concentration — units = (mg ÷ mg/mL) × 100. Deep dive →

Verification status. Our three-tier honesty label on every figure: operator-supplied, third-party reported, or verified at checkout.

ATTAIN. Orforglipron's phase-3 obesity program; ATTAIN-1's ~12.4% average loss is the number behind every Foundayo comparison.

Bioavailability. The fraction of a dose that reaches circulation. Oral peptides sit near 1% (Rybelsus-class) — the physics every compounded 'tirzepatide tablet' claim runs into.

Cash-pay. Buying outside insurance entirely — the lane LillyDirect vials, NovoCare pricing, and the compounded market compete in.

Formulary. Your plan's covered-drug list, with tiers and restriction codes (PA, QL, ST) — the first document any coverage question opens.

Formulary exception. A prescriber-filed request to cover an off-formulary drug — the tool for 'not on formulary' rejections, cousin to the PA appeal.

Gastric emptying. How fast the stomach hands food onward. GLP-1 drugs slow it — the mechanism behind fullness, several side effects, the oral-contraceptive caveat, and pre-surgery holds.

Letter of medical necessity. The prescriber's appeal document: clinical picture, prior attempts, and the case for this agent — the load-bearing wall of overturned denials.

NovoCare. Novo Nordisk's direct-to-patient channel; source of oral Wegovy's ~$149 flat self-pay price, the cheapest brand GLP-1 in the U.S.

Orforglipron. The non-peptide small-molecule GLP-1 agonist in Foundayo — swallowable without food/water rules precisely because it isn't a peptide.

Steady state. The stable drug level reached after ~4–5 weekly doses (five half-lives) — why week five feels different from week one and why judging any dose takes a month.

Step therapy. An insurer's 'fail cheaper drugs first' requirement — increasingly waived for GLP-1s and contestable with a medical-necessity letter.

Subcutaneous (SubQ). Injection into the fat layer under the skin — tirzepatide's route; abdomen, thigh, or upper arm, rotated weekly.

Washout. The clearance period after stopping — ~25–30 days for tirzepatide — governing pregnancy timing, drug switches, and why week two off the drug proves nothing.

45-day window. LillyDirect's refill condition on the $449 vial tier: reorder within 45 days or the price can spike toward list — the fine print that turns a discount into a schedule.

Missing a term you've hit in the wild? Send it — the glossary grows with the market's vocabulary, including the euphemisms.