What Is a GLP-1 Medication, and How Does It Work for Weight Loss?

Does a GLP-1 medication come as a pill or an injection?

Both forms exist, but not for every brand — Wegovy is available as an injection or a tablet, while Zepbound and Mounjaro (tirzepatide) are injection-only. Wegovy is marketed in two distinct dosage forms under a single brand name and a single FDA label: WEGOVY (semaglutide) injection, solution, and WEGOVY (semaglutide) tablet. Wegovy injection is administered subcutaneously in the abdomen, thigh, or upper arm, once weekly on the same day each week, with or without meals. Wegovy tablets are taken orally once daily on an empty stomach in the morning with up to 4 ounces of water; the patient must wait at least 30 minutes before eating food, drinking other beverages, or taking other oral medications. Both forms carry a weight indication: Wegovy tablets are indicated, in combination with a reduced calorie diet and increased physical activity, to reduce excess body weight in adults with obesity or with overweight in the presence of at least one weight-related comorbid condition.

Zepbound is administered exclusively as a subcutaneous injection; the FDA label describes it only as 'injection, for subcutaneous use' and no oral dosage form of Zepbound is listed in the label. The same is true of the diabetes-labeled tirzepatide product: Mounjaro is an injection for subcutaneous use only; it is not an oral tablet or capsule.

If anyone offers you an oral tirzepatide, that product does not correspond to any FDA-approved dosage form on these labels.

Is a GLP-1 medication approved for weight loss or for diabetes?

It depends on the brand — Zepbound and Wegovy carry a weight-loss indication, while Mounjaro and Ozempic are approved only for type 2 diabetes. Zepbound (tirzepatide) is FDA-indicated, in combination with a reduced-calorie diet and increased physical activity, to reduce excess body weight and maintain weight reduction long term in adults with obesity, or adults with overweight in the presence of at least one weight-related comorbid condition. The obesity eligibility threshold used in the Zepbound weight-reduction registration trials was a BMI of 30 kg/m2 or greater. The overweight eligibility threshold used in the Zepbound weight-reduction registration trials was a BMI of 27 to less than 30 kg/m2 together with at least one weight-related comorbid condition.

The diabetes-labeled products are different. Mounjaro's FDA-approved indication is limited to glycemic control in type 2 diabetes mellitus; chronic weight management is not an approved indication under the Mounjaro label. OZEMPIC injection is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. Same molecule in each pair, different label, different coverage — see Mounjaro vs. Zepbound and Ozempic vs. Wegovy for the full side-by-side.

What did the clinical trials show?

In registration trials, semaglutide produced -14.9% body weight change at week 68 and tirzepatide produced -20.9% at week 72 — the numbers behind the class's weight-loss claims. In the STEP 1 trial, mean change in body weight from baseline to week 68 was -14.9% with once-weekly subcutaneous semaglutide 2.4 mg versus -2.4% with placebo, in 1,961 adults with overweight or obesity without diabetes (figures as of August 2026). In STEP 1, 86.4% of participants (1,047) receiving semaglutide 2.4 mg achieved at least 5% weight loss at week 68, versus 31.5% (182) receiving placebo (figures as of August 2026).

In SURMOUNT-1 (72 weeks, adults with obesity or overweight without type 2 diabetes), mean percent change in body weight was -15.0% with tirzepatide 5 mg, -19.5% with 10 mg, and -20.9% with 15 mg, versus -3.1% with placebo (P<0.001 for all comparisons), as published in 2022.

The oral form has its own trial. In the OASIS 4 trial, mean change in body weight at week 64 was -13.6% with oral semaglutide 25 mg once daily versus -2.2% with placebo (estimated difference -11.4 percentage points), in a 71-week trial of 307 adults (205 semaglutide, 102 placebo), reported as of August 2026.

What happens when you stop matters too. In the Zepbound label's Study 4, a 52-week randomized withdrawal trial, patients continuing Zepbound from Week 36 to Week 88 had a further -5.5% body weight change while patients switched to placebo regained +14.0% (label data as of August 2026).

How is the dose increased on a GLP-1 medication?

Every GLP-1 in this class starts low and increases gradually over weeks to reduce side effects — Wegovy over 16 weeks, Zepbound in 4-week steps. Wegovy injection is escalated on a 4-week-per-step schedule: 0.25 mg once weekly for weeks 1-4, 0.5 mg for weeks 5-8, 1 mg for weeks 9-12, 1.7 mg for weeks 13-16, then a maintenance dose from week 17 onward. For weight reduction in adults, the Wegovy injection maintenance dose is 1.7 mg or 2.4 mg once weekly, and may be increased to a maximum of 7.2 mg once weekly if further weight reduction is needed and the dose is tolerated.

The recommended starting dosage of Zepbound for all indications is 2.5 mg injected subcutaneously once weekly for 4 weeks; the 2.5 mg dosage is for treatment initiation and is not approved as a maintenance dosage. After 4 weeks at 2.5 mg, the Zepbound dosage is increased to 5 mg subcutaneously once weekly, and may thereafter be increased in 2.5 mg increments after at least 4 weeks on the current dose. For the weight-reduction indication, the recommended Zepbound maintenance dosages are 5 mg, 10 mg, or 15 mg injected subcutaneously once weekly.

What are the side effects and safety warnings of GLP-1 medications?

GI side effects are the most common across the class, and both Wegovy and Zepbound carry the same thyroid C-cell tumor boxed warning. The most common adverse reactions (incidence at or above 5%) in adults or pediatric patients aged 12 years and older are nausea, diarrhea, vomiting, constipation, abdominal pain, dysesthesia, headache, fatigue, dyspepsia, dizziness, abdominal distension, eructation, hypoglycemia in patients with type 2 diabetes, flatulence, gastroenteritis, gastroesophageal reflux disease, and hair loss, per the Wegovy prescribing information as of August 2026.

In the Zepbound weight-reduction trials, nausea was reported by 25% of patients on 5 mg, 29% on 10 mg, and 28% on 15 mg, versus 8% on placebo, per the FDA label as of August 2026.

Both drugs carry a boxed warning, per the Wegovy and Zepbound prescribing information. Wegovy carries a boxed warning for risk of thyroid C-cell tumors: in rodents, semaglutide causes dose-dependent and treatment-duration-dependent thyroid C-cell tumors at clinically relevant exposures. Zepbound carries a boxed warning for risk of thyroid C-cell tumors: in rats, tirzepatide causes thyroid C-cell tumors, and it is unknown whether Zepbound causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans.

Wegovy is contraindicated in patients with a personal or family history of medullary thyroid carcinoma (MTC) and in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Zepbound is contraindicated in patients with a personal or family history of medullary thyroid carcinoma (MTC) or in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).

Why is the same drug covered for one person and denied for another?

Payers reimburse against a formulary and an indication, not the mechanism — but the indication is only a starting point, not the whole story. A formulary is the list of prescription drugs covered by a prescription drug plan or other insurance plan offering prescription drug benefits, and plans can still layer on utilization management such as step therapy, quantity limits, or extra diagnosis documentation on top of the indication match. (More in does insurance cover GLP-1 weight loss medications.)

Preauthorization is a decision by a health insurer or plan that a health care service, treatment plan, prescription drug, or durable medical equipment is medically necessary — sometimes called prior authorization, prior approval, or precertification. Preauthorization is not a promise that the health insurance plan will cover the cost of the service or drug.

Measured states that many insurance plans require a prior authorization before they will cover brand-name GLP-1s such as Ozempic, Wegovy, Mounjaro, or Zepbound. For patients with commercial insurance, Measured performs a benefits check to determine which medications may be covered under the patient's plan, and Measured's insurance concierge team submits prior authorizations on the patient's behalf and keeps the patient updated on the insurance plan's determination. Coverage is decided by the plan, not by Measured, and no outcome is guaranteed. Measured names Aetna, Anthem, Blue Cross Blue Shield, Cigna, and UnitedHealthcare as commercial insurance plans it helps eligible patients use to obtain GLP-1 coverage when available through their benefits.

Costs, all as of August 5, 2026: Measured states that while many patients have GLP-1 copays around $20, actual out-of-pocket cost depends on the patient's specific insurance plan and pharmacy benefits. Novo Nordisk states a list price of $1,349.02 per package for the Wegovy pill, the Wegovy pen, and the Wegovy HD pen; list price is the manufacturer price before discounts or rebates, and most insured patients pay less. Measured membership fees are not covered by insurance and are paid separately.

For most Marketplace and employer-sponsored plans, an enrollee must file an internal appeal within 180 days (6 months) of receiving notice that the claim was denied; Medicare, Medicaid, and some other plan types run on different appeal timelines, so confirm the deadline on your own denial notice.

Is compounded semaglutide or tirzepatide the same as the brand-name drug?

No — compounded medications are not reviewed or approved by the FDA for safety or effectiveness. Measured states that providers may prescribe them in certain cases to address patient-specific needs or when commercially available medications are not appropriate or available. As of August 5, 2026, Measured lists Compounded Semaglutide as "No insurance required" with medication included in the membership price, from $119/mo, and Compounded Tirzepatide as "No insurance required" with medication included in the membership price, from $219/mo.

Who is eligible for a GLP-1 medication?

The FDA-approved weight-management medications are labeled for adults with obesity, or adults with overweight in the presence of at least one weight-related comorbid condition. The registration trials behind those indications enrolled adults with obesity defined as a BMI of 30 kg/m² or greater, or overweight defined as 27 to under 30 kg/m² alongside a comorbid condition such as dyslipidemia, hypertension, obstructive sleep apnea, or cardiovascular disease.

A telehealth program's own enrollment criteria are a separate matter and may be broader than the labeled population. Meeting them is not the same as a medication being indicated for you — that is a clinical decision a licensed provider makes after evaluating you, and the answer may be that no medication is appropriate.

Per Measured's Help Center, Measured is available in 26 states, which it says allows it to serve roughly 80% of the U.S. population (as of August 5, 2026).

What this page does not cover

We have not described the receptor-level physiology — how GLP-1 receptor activity translates into appetite change, gastric emptying, or insulin release. That belongs with your prescriber and the prescribing information for your specific product.

One area of active research is what GLP-1 receptors in the reward circuitry of the brain do beyond appetite. We cover the early evidence on whether GLP-1 medications can treat addiction separately.