Wegovy (Semaglutide) Complete Guide — Effects, Side Effects, Korean Launch, and Who It's Prescribed For

Let's break down GLP-1 obesity drugs once and for all

Lately, names like 'Wegovy' and 'Mounjaro' come up often in diet conversations. These are obesity medications that use a hormone called GLP-1. Contrary to what some people believe, they are not diet supplements you can easily buy at a pharmacy — they are prescription drugs that require a doctor's prescription. This article is a neutral, general-information piece on what these drugs are, how they work, and what to watch out for.

What is Wegovy?

Wegovy is an obesity medication from Novo Nordisk, and its active ingredient is semaglutide. It is administered as a once-weekly subcutaneous injection (a pen-type self-injection) and is indicated for the treatment of obesity. It launched in Korea in 2024. Within the same Novo Nordisk family, the diabetes drug Ozempic (semaglutide) and the once-daily obesity drug Saxenda (liraglutide) also belong to the same GLP-1 drug class.

How does it cause weight loss — the mechanism of action

GLP-1 is originally a hormone our body secretes after eating, and it is involved in satiety and blood sugar regulation. Drugs like Wegovy act similarly to this hormone and reduce food intake in two ways. That is, they act on the appetite center of the brain to suppress appetite, and they delay gastric emptying (the rate at which food leaves the stomach) so you feel full for longer. As a result, you naturally eat less and lose weight.

How is Mounjaro (tirzepatide) different?

Mounjaro is a drug from Eli Lilly, and its active ingredient is tirzepatide. Unlike Wegovy, which acts only on GLP-1, it is a 'dual-action' drug that acts simultaneously on two hormone receptors — GIP and GLP-1 — and is injected once weekly. In Korea, Mounjaro was launched with a diabetes indication (launched 2024–2025), while in the United States the same ingredient is approved for an obesity indication under a separate brand name, 'Zepbound.' It's worth remembering that the same ingredient can have different brands and approved indications depending on the country.

When will an oral GLP-1 obesity drug be available?

For people who find injections daunting, 'oral GLP-1 obesity drugs' are being developed. A representative example is Eli Lilly's orforglipron, which is reported to have completed Phase 3 clinical trials and to be in the approval process (development and review) stage. However, it has not yet been generally launched, and the specific launch date, price, and domestic brand name have not been finalized and may change. Specific product names or launch timings circulating on the internet may be inaccurate, so if you are interested, please check official announcements and the latest news.

Who is it prescribed for — indications and target patients

These drugs are not for everyone to use for cosmetic purposes; they are prescribed under a physician's judgment to obese or overweight patients who meet certain medical criteria. Generally, eligible patients include those whose body mass index (BMI) is above a certain threshold, or those who are overweight and have comorbidities such as hypertension, diabetes, or dyslipidemia. The specific criteria vary by drug, country, and approval terms, so whether you qualify must be confirmed through a doctor's examination.

Major side effects and contraindications

• The most common side effects are gastrointestinal issues — nausea, vomiting, diarrhea, constipation, and so on, which may appear especially in the early period when the dose is being increased.
• More rarely, side effects requiring greater caution, such as pancreatitis and gallstones (gallbladder disease), have been reported.
• In animal (rodent) studies, thyroid C-cell tumors were observed, so a boxed warning (the strongest level of warning) is displayed.
• Use is contraindicated for those with a personal or family history of medullary thyroid carcinoma, or with multiple endocrine neoplasia type 2 (MEN2).
• If abnormal symptoms appear, do not try to endure them on your own — consult the prescribing doctor or pharmacist immediately.

Practical precautions you must know

1. It is not a diet supplement. It must only be used after a doctor's examination and prescription, and only when the indications are met.
2. Misuse for cosmetic purposes, and unauthorized purchase and use through overseas direct purchase or secondhand trading, are dangerous in terms of both safety and authenticity.
3. If you stop, your appetite may return and your weight may increase again — a 'weight rebound.' The medication must go hand in hand with lifestyle management such as diet and exercise.
4. If prescribed as a non-reimbursed treatment, the cost can be quite high. Whether it is covered by insurance and its price vary by timing and product, so you need to check directly.

In summary

GLP-1 class drugs such as Wegovy and Mounjaro are obesity medications that reduce intake through appetite suppression and delayed gastric emptying. As much as clear effects are reported, they also come with real-world limitations: side effects like gastrointestinal problems, contraindications, cost, and rebound after discontinuation. The key point is that these drugs are not 'miracle diet pills' but prescription medications used under a doctor's management according to medical criteria.

Disclaimer (please read)

This article is for general medical-information reference only and does not replace the recommendation of any specific product, nor diagnosis or prescription. Whether to pursue obesity treatment, your choice of medication, and starting, stopping, or changing oral or injection use must be decided in consultation with a doctor or pharmacist. A drug's launch, price, reimbursement, and approval status may change, so please check the latest official information.