Which department should I see for unexplained weight loss?

2026-09-17 · Neutral information that names no hospital, doctor or region. No rankings, recommendations or reviews.

Which department

1. 1Internal Medicine (내과)
   Internal Medicine serves as the primary entry point for unexplained weight loss because it can broadly evaluate systemic causes — including hormonal imbalances, chronic infections, inflammatory conditions, and nutritional issues — before narrowing down to a specific specialty. — First / second line: In general, visiting a local internal medicine clinic (내과 의원) first is a reasonable approach. If initial evaluation suggests a specific organ system is involved, the clinic doctor will typically issue a referral (진료의뢰서) to a secondary or tertiary hospital.
2. 2Endocrinology (내분비내과)
   Endocrinology focuses on hormone-related disorders such as thyroid disease or diabetes, both of which are common causes of unintended weight loss. If blood tests suggest abnormal hormone levels, an internist may refer you here. — First / second line: This department is usually reached via referral from Internal Medicine rather than as a first visit, particularly when hormonal abnormalities are suspected based on preliminary findings.
3. 3Gastroenterology (소화기내과)
   Gastroenterology addresses conditions affecting the digestive tract — such as malabsorption, inflammatory bowel disease, or structural issues — which can all lead to unintended weight loss, especially when accompanied by digestive symptoms. — First / second line: A visit to Gastroenterology is generally recommended when weight loss is accompanied by symptoms such as persistent nausea, changes in bowel habits, or abdominal discomfort, often following an initial assessment by Internal Medicine.
4. 4Hematology-Oncology (혈액종양내과)
   Hematology-Oncology evaluates blood disorders and cancers, some of which can present as significant, unexplained weight loss without obvious digestive or hormonal causes. This specialty is typically involved when other common causes have been ruled out. — First / second line: This department is almost always reached through referral after initial workup at Internal Medicine, and is not typically the first stop for unexplained weight loss on its own.

Go to the ER / call 119 if

Before your visit

• Record approximately when the weight loss started and how many kilograms have been lost over what period of time.
• Note any accompanying symptoms such as fatigue, changes in appetite, fever, digestive discomfort, or mood changes.
• Prepare a list of all medications, supplements, and herbal products you are currently taking, including dosages.
• Bring any previous medical records, blood test results, or imaging reports that may be relevant.
• Think about any recent major life changes such as stress, dietary shifts, travel history, or new health conditions.
• Note your eating and drinking habits over the past few weeks, including any foods you have been avoiding.

General principles

Unexplained weight loss — generally defined as losing a meaningful amount of body weight without intentional dieting or increased exercise — is considered a nonspecific symptom, meaning it can arise from many different organ systems. Because of this, Internal Medicine (내과) is typically the starting point, as it allows a broad assessment before directing care to a more specialized department.

In the Korean healthcare system, the general flow begins at a local clinic (의원, 1차 의료기관), where a doctor takes a history, performs a physical exam, and may order basic tests. If the cause is not clear or requires specialized care, a referral letter (진료의뢰서) may be issued to a secondary or tertiary hospital (병원 or 종합병원); note that while secondary hospitals can be visited directly with standard insurance coverage, a referral is required for insurance coverage purposes specifically at tertiary hospitals (상급종합병원).

The range of conditions that can cause unexplained weight loss is broad — from thyroid disorders and diabetes to digestive diseases, chronic infections, and less commonly, malignancies. A doctor will typically follow a stepwise approach, beginning with common and treatable causes before considering rarer ones. The specific sequence of evaluations is determined by the consulting physician based on the full clinical picture.

Weight loss that occurs alongside other symptoms — such as night sweats, persistent fatigue, or changes in bowel habits — may help the doctor identify which specialty to involve sooner. Presenting a clear timeline and symptom history at your first visit can significantly help the clinical evaluation process.

FAQ

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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)