GLP-1 medications

What it is

GLP-1 medications are injectable (or oral) drugs that mimic the gut hormone GLP-1 (glucagon-like peptide-1) to lower blood sugar, reduce appetite, and promote weight loss. GLP-1 is an incretin hormone — a chemical released by the intestines after eating that signals the pancreas to produce insulin. This drug class includes semaglutide (Ozempic, Wegovy, Rybelsus), liraglutide (Victoza, Saxenda), dulaglutide (Trulicity), exenatide (Byetta, Bydureon), and tirzepatide (Mounjaro, Zepbound). Tirzepatide is technically a dual GLP-1/GIP agonist, meaning it activates two incretin receptors rather than one, but it is widely grouped with GLP-1 medications in clinical practice.

Causes and mechanism

After a meal, the gut releases GLP-1, which triggers insulin secretion, suppresses glucagon (a hormone that raises blood sugar), slows gastric emptying (how fast food leaves the stomach), and signals the brain's appetite centers to reduce hunger. GLP-1 medications bind to the same receptor and produce these effects at sustained, pharmacologic levels. Because insulin release is glucose-dependent — meaning it only occurs when blood sugar is elevated — the risk of dangerously low blood sugar (hypoglycemia) is low when these drugs are used alone.

Symptoms and diagnosis

These medications treat conditions rather than cause them, so there is no "diagnosis" for GLP-1 use itself. FDA-approved indications include:

• Type 2 diabetes (T2DM): when blood sugar remains above target despite lifestyle changes, or when A1c is more than 1.5% above goal.
• Chronic weight management: BMI ≥ 30, or BMI ≥ 27 with at least one weight-related condition (e.g., hypertension, sleep apnea, dyslipidemia).
• Cardiovascular risk reduction: semaglutide is approved to lower major cardiovascular events in adults with T2DM and established heart disease.

A clinician will typically check fasting glucose, HbA1c, kidney function, and thyroid history before prescribing.

Treatment options

Drug	Route	Frequency	Primary approval
Semaglutide (Ozempic)	Injection	Weekly	T2DM, CV risk
Semaglutide (Wegovy)	Injection	Weekly	Obesity
Semaglutide (Rybelsus)	Oral tablet	Daily	T2DM
Tirzepatide (Mounjaro)	Injection	Weekly	T2DM
Tirzepatide (Zepbound)	Injection	Weekly	Obesity
Liraglutide (Saxenda)	Injection	Daily	Obesity
Dulaglutide (Trulicity)	Injection	Weekly	T2DM

Clinical trials show semaglutide produces roughly 15% body weight loss at 68 weeks (STEP 1 trial), while tirzepatide produces up to 22.5% at 72 weeks (SURMOUNT-1 trial). These figures apply to people with obesity without diabetes; results vary with dose and adherence.

Common side effects — nausea, vomiting, diarrhea — are most pronounced during dose escalation and typically improve over weeks. Serious but rare concerns include pancreatitis, gallbladder disease, and, based on animal data, a theoretical risk of medullary thyroid carcinoma. These drugs are contraindicated in personal or family history of medullary thyroid cancer or multiple endocrine neoplasia type 2, and during pregnancy.

Researchers are actively studying muscle mass loss during rapid weight loss on these agents; current evidence suggests combining resistance exercise and adequate protein intake helps preserve lean mass, though long-term data are still accumulating.

When to see a clinician

Seek evaluation if you have T2DM with an A1c above your target after 3 months of first-line therapy, a BMI of 27 or higher with a weight-related health condition, or established cardiovascular disease alongside obesity or T2DM. Contact your prescriber promptly if you develop persistent abdominal pain (possible pancreatitis), severe vomiting causing dehydration, or a new neck lump. Do not start, stop, or adjust doses without medical supervision — dose titration schedules exist specifically to minimize side effects.