The GLP-1 dictionary
Every term you'll meet during GLP-1 treatment — from your prescriber, in support groups, and online — defined in plain language, with links to the full guides where one exists.
A1C
A blood test showing your average blood sugar over ~3 months. The key number for diabetes management — and a common non-scale victory on GLP-1s.
BMI
Body mass index — weight over height squared. The number insurers use to gate GLP-1 coverage, and a useful-but-crude measure with real blind spots.
Body recomposition
Losing fat while keeping (or gaining) muscle, so your shape changes even when the scale barely moves. Why measurements can beat weight as a progress signal.
Compounded semaglutide
Semaglutide made by compounding pharmacies rather than the brand manufacturer. Cheaper and widely used during shortages — but not FDA-approved, with real quality and safety caveats.
Constipation
The other big GI side effect after nausea — driven by slower digestion plus eating and drinking less. Mostly solved with fiber, fluids, and movement.
Fatigue
Tiredness some people feel on GLP-1s, especially early or after dose increases. Usually a downstream effect of eating far less — often fixable.
Food noise
The constant, intrusive mental chatter about food — thinking about the next meal while still eating this one. The term people most often use to describe what GLP-1 medications switch off.
Gallstones
Hardened deposits in the gallbladder made more likely by rapid weight loss — on or off GLP-1s. Known cause, known symptom pattern, partly preventable.
Gastric emptying
How fast food leaves your stomach. GLP-1 medications slow it down — the direct cause of both early fullness and most nausea.
Gastroparesis
Severely delayed stomach emptying — an extreme of the effect GLP-1s produce on purpose. Usually mild and reversible, but a symptom pattern worth knowing.
GIP
Glucose-dependent insulinotropic polypeptide — the second gut hormone that tirzepatide (Zepbound, Mounjaro) targets alongside GLP-1.
GLP-1
Glucagon-like peptide-1 — the natural gut hormone these medications imitate. It signals fullness, slows digestion, and helps control blood sugar.
Hair loss (telogen effluvium)
Temporary hair shedding some people notice a few months into treatment. It's driven by rapid weight loss, not the drug directly — and it regrows.
Half-life
How long it takes for half a dose to clear your body. Semaglutide's ~7-day half-life is why it's dosed weekly — and why missed doses have catch-up windows.
Hypoglycemia
Low blood sugar. Uncommon from GLP-1s alone, but the risk rises sharply when combined with insulin or sulfonylureas — a key reason to tell every prescriber you're on one.
Injection site rotation
Changing where you inject each week — abdomen, thigh, or upper arm — to keep skin healthy and absorption consistent.
Injection-site reaction
Redness, itching, or a small bump where you injected. Usually minor and short-lived — distinct from the lumpy tissue that poor site rotation causes.
Lean mass loss
The portion of weight lost that comes from muscle and other non-fat tissue rather than fat. A key reason protein intake and strength training matter during GLP-1 treatment.
Liraglutide (Saxenda, Victoza)
The first-generation GLP-1 medication — a daily injection rather than weekly. Largely superseded by semaglutide and tirzepatide, but still prescribed.
Maintenance dose
The dose you stay on long-term after titration ends — not necessarily the maximum dose, but the one that balances results and side effects for you.
Metabolic adaptation
The way your body burns fewer calories as you lose weight — beyond what the smaller size alone predicts. A real reason weight loss slows and regain is easy.
Microdosing
Using GLP-1 doses below the standard schedule — a popular community practice for maintenance or side-effect control that is off-label and largely unstudied.
Non-scale victory (NSV)
A sign of progress the scale can't show — looser clothes, better bloodwork, more stamina. The antidote to plateau panic and daily weigh-in obsession.
Off-label
Prescribing a drug for a use the FDA hasn't formally approved — like Ozempic for weight loss. Legal and common, but it affects insurance coverage.
Ozempic face
The gaunt, deflated facial look attributed to rapid weight loss — facial fat loss, not a drug side effect. The term, not the biology, is what's new.
Pancreatitis
Inflammation of the pancreas — a rare but serious GLP-1 warning. The key is recognizing the one symptom that means stop and seek care: severe, persistent belly pain.
Pen storage (cold chain)
GLP-1 pens are refrigerated medications with specific temperature limits — including how long they can stay out of the fridge, which matters for travel.
Prior authorization
The insurer's approval step before they'll cover a GLP-1. Understanding it — and documenting your case — is often what gets a prescription paid for.
Protein-first eating
Eating the protein on your plate before anything else — the standard strategy for hitting protein targets when GLP-1 appetite suppression shrinks your meals.
Rebound weight gain
Weight regain after stopping GLP-1 medication. In the STEP 1 extension, participants regained about two-thirds of lost weight within a year of stopping.
Retatrutide
An investigational "triple agonist" (GLP-1 + GIP + glucagon) in clinical trials. Early results are striking, but it is not yet approved — one to watch, not to seek.
Rybelsus (oral semaglutide)
Semaglutide in a daily pill instead of an injection. Same molecule as Ozempic, approved for type 2 diabetes, with strict timing rules for absorption.
Sarcopenia
Age-related loss of muscle mass and strength. Rapid weight loss can accelerate it — the main reason muscle protection matters most for older adults on GLP-1s.
Savings card (copay card)
Manufacturer discount programs that can lower the out-of-pocket cost of brand-name GLP-1s. Real savings, with eligibility fine print worth reading.
Semaglutide
The GLP-1 receptor agonist behind Ozempic, Wegovy, and Rybelsus. In the STEP 1 trial, weekly 2.4 mg semaglutide produced ~15% average weight loss over 68 weeks.
Set point
The weight range your body defends by adjusting hunger and metabolism. The leading explanation for why weight is regained — and why GLP-1s may work by lowering it.
Sharps container
The puncture-proof container for used needles and pens. Simple, cheap, and the safe (often legally required) way to dispose of injection waste.
Shot day
The fixed day each week when you take your GLP-1 injection. The anchor of the weekly treatment rhythm — and the day most worth tracking.
Sulfur burps
Burps that smell like rotten eggs — an unpleasant but usually harmless GLP-1 side effect, tied to slowed digestion. Sometimes a warning sign worth checking.
Supply and shortages
GLP-1 demand has repeatedly outpaced supply, causing intermittent shortages. They drive dose gaps, pharmacy-hopping, and the rise of compounded versions.
Thyroid (boxed warning)
The FDA boxed warning on GLP-1s about thyroid C-cell tumors, based on rodent studies. What it means, who it excludes from treatment, and how to read it honestly.
Tirzepatide
The dual GIP/GLP-1 receptor agonist behind Zepbound and Mounjaro. In SURMOUNT-1, the highest dose produced ~21% average weight loss over 72 weeks.
Titration
The scheduled step-up from a low starting dose to your target dose, usually in 4-week increments. Designed to let your body adapt and keep side effects manageable.
Traveling with GLP-1s
How to keep your medication safe and your schedule intact on trips: pen storage limits, flying with needles, and handling time-zone shot days.
Weight-loss plateau
The point where weight loss levels off despite continuing treatment. On GLP-1s this is expected and visible in the trial curves — usually after 12–18 months.
Want the full picture, not just the words?
Our guides cover shot day, side effects, eating, and plateaus in practical depth.
Browse all guides