7 Things to Know Before Using GLP-1 Weight-Loss Drugs — Prescriptions, Side Effects, Out-of-Pocket Costs, Rebound Weight Gain After Stopping, and Misuse Risks

GLP-1 Weight-Loss Drugs Are Prescription Medicines, Not Diet Supplements

GLP-1 weight-loss treatments such as Wegovy and Mounjaro have recently attracted major attention. However, these are not diet supplements that can be freely bought at a pharmacy; they are prescription medicines that require a doctor’s diagnosis and prescription. Before focusing only on their effects, a safer starting point is to understand the prescription criteria, side effects, costs, changes after stopping, and risks of misuse in a balanced way.

1. What medicines are they — Wegovy, Mounjaro, and the outlook for oral drugs

• Wegovy (semaglutide, Novo Nordisk): a once-weekly subcutaneous injection launched in Korea in 2024 for the indication of obesity treatment. Related Novo Nordisk products include Ozempic and Saxenda.
• Mounjaro (tirzepatide, Eli Lilly): a once-weekly injectable dual-action drug that acts on both GIP and GLP-1. It is approved in Korea for a diabetes indication under the name Mounjaro and in the United States for an obesity indication under the name Zepbound, with its Korea launch occurring around 2024~2025.
• Oral GLP-1 weight-loss drugs: Eli Lilly’s orforglipron has completed phase 3 clinical trials and is in the approval process stage, meaning it is still under development and review. It has not yet been generally launched, and the specific launch date, price, and domestic brand name have not been finalized and may change — check the latest news.

2. How they work — appetite suppression and delayed gastric emptying

GLP-1 drugs work by mimicking hormones involved in appetite and blood-sugar regulation. Their key mechanism is to act on appetite-control signals in the brain to increase fullness and slow the speed at which food leaves the stomach, so you feel full longer even after eating less. As a result, total calorie intake may decrease and lead to weight loss. However, this is an aid that reduces appetite; it does not replace diet, exercise, and lifestyle management.

3. Not everyone can get a prescription — indications and criteria

These medicines are not intended for minor cosmetic weight loss. They are treatments prescribed at a doctor’s discretion to patients who meet indications such as obesity or diabetes. In general, eligibility is determined based on factors such as body mass index (BMI) and the presence of comorbidities, but specific criteria differ by medicine and country, and medical professionals make decisions after evaluating each person’s condition.

4. Common side effects and rare but important risks

• The most common side effects are gastrointestinal, including nausea, vomiting, diarrhea, and constipation, especially early on when the dose is being increased.
• Rarely, pancreatitis and gallstones or gallbladder disease have been reported. Persistent severe abdominal pain requires immediate medical care.
• Boxed warning, the strongest warning: thyroid C-cell tumors were observed in animal studies involving rodents, so these drugs are contraindicated in people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2 (MEN2).
• Depending on the individual, interactions may occur with other medicines or underlying conditions, so you should tell your medical team about all medicines you are taking.

5. They can be expensive because they may not be covered by insurance

GLP-1 drugs used for obesity treatment are often prescribed as non-covered treatments not reimbursed by health insurance, so out-of-pocket costs can be substantial. They also tend to require continued use to maintain effects, so costs can accumulate. Specific prices and insurance coverage vary by medicine, timing, and medical institution, so it is best to confirm the actual cost before receiving a prescription. (This article does not state any specific price as definitive.)

6. Weight can come back after stopping (rebound)

Because these medicines work by suppressing appetite while they are being used, appetite and weight may return or rebound after stopping them. Rather than thinking of them as “lose it once and you’re done,” a long-term management perspective is needed. It is also advisable to discuss a stopping plan with medical professionals and combine it with lifestyle strategies such as diet and exercise. Effects and the degree of rebound vary greatly by individual, so it is hard to expect clinical average figures to apply equally to everyone.

7. Be especially cautious about misuse and unsupervised use

• Medicines obtained through abnormal channels such as overseas direct purchase or online buying are risky because authenticity, storage conditions, and dosage cannot be verified or controlled.
• Side-effect risks increase if someone who does not meet the indications uses them for cosmetic purposes or ignores the recommended dose and titration schedule.
• There are situations in which these medicines should not be used, such as during pregnancy or breastfeeding, or in people with certain diseases or contraindicated medical histories — do not decide on your own.
• Medicines are not magic solutions, and even clinical averages should be interpreted cautiously as “about this much,” with individual differences assumed.

Key points to remember (summary)

1. They are prescription medicines and require a doctor’s prescription when appropriate — not supplements.
2. Wegovy (semaglutide) and Mounjaro (tirzepatide) are injectables, while an oral drug, orforglipron, is still in development and approval stages.
3. They work by reducing intake through appetite suppression and delayed gastric emptying.
4. Common gastrointestinal problems, rare pancreatitis and gallstones, and a history of medullary thyroid carcinoma or MEN2 are contraindications.
5. They can be expensive as non-covered treatments, and weight may rebound after stopping.
6. Overseas direct purchase and unsupervised cosmetic use are risky — consult a professional whenever possible.

Disclaimer

This article is for general medical information only and does not replace medical diagnosis or prescription. Decisions to start, stop, or change the dose of any medicine, including GLP-1 weight-loss drugs, should be made in consultation with a doctor or pharmacist whenever possible. Drug information, launch status, prices, and insurance coverage may change, so please check the latest official information and guidance from medical professionals.