From the Guidelines
For unexplained weight loss, I recommend ordering a comprehensive laboratory panel including complete blood count (CBC), comprehensive metabolic panel (CMP), thyroid function tests (TSH, free T4), hemoglobin A1C, urinalysis, and inflammatory markers like ESR and CRP, as suggested by the most recent guidelines 1. When evaluating a patient with unexplained weight loss, it is essential to consider a broad range of potential causes, including metabolic disorders, malignancies, chronic infections, gastrointestinal diseases, and psychological conditions.
Initial Evaluation
The initial evaluation should include a comprehensive review of systems, as recommended by the American Psychiatric Association 1. This review should assess for signs of malnutrition, purging behaviors, and other co-occurring health conditions.
Laboratory Tests
The laboratory assessment should include:
- Complete blood count (CBC) to identify anemia, infections, or malignancies
- Comprehensive metabolic panel (CMP) to evaluate liver and kidney function, electrolyte balance, and nutritional status
- Thyroid function tests (TSH, free T4) to rule out hyperthyroidism, which is a common cause of weight loss
- Hemoglobin A1C to screen for diabetes, which can present with weight loss despite increased appetite
- Urinalysis to detect diabetes, infection, or kidney disease
- Inflammatory markers like ESR and CRP to indicate chronic inflammatory conditions or occult malignancy Additional tests should be considered based on the clinical context, such as:
- Fecal occult blood testing
- HIV screening
- Age-appropriate cancer screenings
- Cortisol levels for adrenal disorders
- Celiac disease antibodies
- Specific tumor markers if cancer is suspected
Specialized Tests
Depending on the clinical context, specialized tests may be necessary to rule out specific conditions. For example, an electrocardiogram may be recommended for patients with a restrictive eating disorder, severe purging behavior, or those taking medications that prolong QTc intervals 1.
Treatment Plan
Patients with unexplained weight loss should have a documented, comprehensive, culturally appropriate, and person-centered treatment plan that incorporates medical, psychiatric, psychological, and nutritional expertise, commonly via a coordinated multidisciplinary team 1.
From the Research
Labs to Order with Unexplained Weight Loss
When approaching patients with unintentional weight loss, a comprehensive workup is necessary to determine the underlying cause 2. The following labs may be ordered:
- Complete Blood Count (CBC) to evaluate the total numbers and characteristics of cell components in the blood, which can help predict the risk of cancer, cardiovascular disease, and metabolic syndrome 3
- Other labs may be ordered based on the patient's clinical presentation and medical history, such as:
- Blood chemistry tests to evaluate liver and kidney function
- Thyroid function tests to rule out thyroid disorders
- Inflammatory marker tests, such as erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP)
- Tests for gastrointestinal disorders, such as celiac disease or inflammatory bowel disease
- Tests for malignancy, such as tumor markers or imaging studies It is essential to note that up to a quarter of patients with unintentional weight loss may not have a diagnosis after comprehensive workup, and close follow-up is warranted 2.