Which department should I see for sudden weight gain or loss?

Name: Which department should I see for sudden weight gain or loss?
Creator: Which Department
Published: 2026-09-16

2026-09-16 · Neutral information that names no hospital, doctor or region. No rankings, recommendations or reviews.

Short answer

Family Medicine(가정의학과) is generally the first department to see for sudden, unexplained weight changes, as it can assess overall health and coordinate further referrals. Depending on the suspected cause, you may be referred to Endocrinology(내분비내과) for hormonal issues or Internal Medicine(내과) for digestive or systemic conditions.

Which department

1Family Medicine (가정의학과)
Family Medicine physicians are trained to evaluate the full range of possible causes behind sudden weight changes, including metabolic, hormonal, lifestyle, and psychological factors. They typically conduct an initial assessment and direct patients to the appropriate specialist based on findings. — First / second line: This is generally the best starting point at a local clinic(의원) for most adults with unexplained weight changes. If the cause requires specialist evaluation, a referral letter(진료의뢰서) will typically be issued for a secondary-level hospital.
2Endocrinology (내분비내과)
Endocrinologists specialize in hormonal and metabolic disorders — such as thyroid dysfunction, diabetes, or adrenal gland conditions — which are among the more common medical causes of sudden weight gain or loss. This department focuses specifically on the endocrine system rather than general health screening. — First / second line: A visit here is generally appropriate after an initial assessment suggests a hormonal or metabolic cause, or if you already have a known endocrine condition. In Korea, a referral from a primary clinic is generally needed to be seen at a larger hospital-level(병원·종합병원) endocrinology department under the standard health insurance(건강보험) system.
3Internal Medicine (내과)
Internal Medicine covers a broad range of organ systems including the gastrointestinal tract, liver, kidneys, and heart, all of which can contribute to weight changes. If digestive symptoms, fluid retention, or signs of systemic illness accompany the weight change, this department may be involved. — First / second line: If prominent accompanying symptoms such as nausea, swelling, or changes in bowel habits are present alongside weight changes, a primary-level Internal Medicine clinic may be a reasonable first visit. Referral to a subspecialty within internal medicine may follow depending on assessment.
4Psychiatry / Mental Health (정신건강의학과)
Conditions such as depression, anxiety, or eating disorders can cause significant and rapid changes in appetite and body weight. When psychological factors are suspected as a primary driver, this department addresses the root cause more directly. — First / second line: This department is generally consulted when weight changes are accompanied by noticeable mood changes, loss of interest, disordered eating patterns, or high stress. A Family Medicine physician may suggest this referral after ruling out physical causes.

Go to the ER / call 119 if

If any of the following applies, do not choose a department — go to an emergency room or call 119 (Korea's emergency number).

Sudden, severe chest pain or difficulty breathing alongside rapid weight change — go to the emergency room or call 119 immediately.
Fainting, loss of consciousness, or extreme confusion accompanying rapid weight loss — seek emergency care without delay.
Rapid and severe swelling of the face, limbs, or abdomen with shortness of breath — go to the emergency room rather than scheduling a regular appointment.
Vomiting blood or passing black or bloody stools together with significant weight loss — this requires immediate emergency evaluation.
Signs of severe dehydration such as no urination, sunken eyes, or inability to keep any fluids down — go to the emergency room or call 119.

Before your visit

Note approximately when the weight change started and how much weight was gained or lost over what period of time.
Think about whether your appetite, diet, or physical activity level has changed recently, and be ready to describe any differences.
Write down all accompanying symptoms, such as fatigue, hair loss, increased thirst, swelling, mood changes, or digestive issues.
Bring a list of all medications, supplements, and herbal remedies you are currently taking, as some can affect body weight.
If you have had a recent health checkup(건강검진) or blood test, bring those results as they can provide useful baseline information.
Consider whether there have been recent major life changes such as significant stress, illness, or changes in sleep patterns that may be relevant.

General principles

Sudden weight gain or loss that is not explained by obvious changes in diet or activity is generally treated as a signal worth investigating medically. Because the causes range widely — from thyroid or adrenal disorders and diabetes to gastrointestinal diseases, cardiac conditions, and mental health concerns — the general approach in Korean primary care is to start with a broad assessment before narrowing to a specific department.

In the Korean healthcare system, starting at a local clinic(의원) is generally recommended before visiting a large hospital. A Family Medicine or Internal Medicine clinic can often order initial blood tests and imaging as part of a general workup, and will issue a referral letter(진료의뢰서) if specialist care is needed. Visiting a large hospital directly without a referral is possible but may involve higher out-of-pocket costs under the national health insurance system.

The diagnostic process for unexplained weight change typically involves gathering a detailed history of the symptom timeline and associated complaints, followed by general blood and urine analyses to look at metabolic, thyroid, kidney, and liver function. The results of these initial steps generally guide which specialist department is consulted next, making the first visit to a generalist an efficient starting point.

Weight changes in older adults and in children may have different common causes compared to working-age adults, and the clinical approach may vary accordingly. For instance, unintentional weight loss in older individuals is often evaluated with a broader differential, and pediatric weight concerns are generally managed within Pediatrics(소아청소년과) rather than adult medicine departments.

FAQ

Should I go to a local clinic or a large hospital first for sudden weight change?

In general, starting at a local clinic(의원) — such as a Family Medicine or Internal Medicine clinic — is the recommended first step in the Korean healthcare system. If initial evaluation suggests a more complex cause, the clinic physician will typically issue a referral letter for a secondary or tertiary hospital. Going directly to a large hospital without a referral is possible but may result in higher costs.

How is sudden weight change different from normal fluctuation, and when should I be concerned?

Minor day-to-day weight fluctuations are common and often related to fluid balance, meals, or activity. As a general principle, a noticeable and sustained change — such as losing or gaining several kilograms over a short period without a clear reason — is worth discussing with a doctor. A medical professional is best placed to judge whether the degree and speed of change warrants further evaluation.

What kinds of tests are generally done for unexplained weight change?

The types of tests conducted vary by the physician's assessment, but general blood tests examining thyroid function, blood sugar, liver, and kidney markers are commonly part of an initial workup for unexplained weight change. Additional tests such as urine analysis or imaging may follow depending on findings. The decision about which tests are appropriate is made by the attending physician after a clinical assessment.

Is the approach different for children or elderly patients with sudden weight change?

Yes, the clinical approach generally differs by age group. For children and adolescents, unexplained weight changes are typically first evaluated within Pediatrics(소아청소년과), where growth and developmental context are considered. For older adults, unintentional weight loss in particular is often assessed with a broader range of possible causes in mind, and the physician will guide the appropriate referral path based on the individual's overall health status.

Find a clinic (external directories)

External directories for finding a clinic by region once you know the department (public data, no rankings or recommendations).

Hospital directory by region (koreahospital.org)

This page is general medical information and does not replace diagnosis, treatment or choosing a clinic. Consult a doctor for any symptom. In an emergency, go to the ER or call 119 immediately.