Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: July 25, 2025 • View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

Differential Diagnosis for an 18-year-old Losing Weight

When considering the differential diagnosis for an 18-year-old experiencing weight loss, it's crucial to approach the situation systematically to ensure that no critical conditions are overlooked. The following categories help organize the potential diagnoses based on their likelihood and the urgency of their potential impact on the patient's health.

  • Single Most Likely Diagnosis
    • Eating disorders (such as anorexia nervosa, bulimia nervosa): These conditions are prevalent among adolescents and young adults, particularly females, and can lead to significant weight loss. The psychological and social pressures during this age can contribute to the development of these disorders.
  • Other Likely Diagnoses
    • Thyroid disorders (hyperthyroidism): An overactive thyroid gland can increase metabolism, leading to weight loss despite increased appetite.
    • Diabetes mellitus (especially type 1): Uncontrolled diabetes can result in weight loss due to the body's inability to use glucose effectively, leading to the breakdown of fat for energy.
    • Gastrointestinal issues (such as celiac disease, Crohn's disease, or ulcerative colitis): These conditions can lead to malabsorption of nutrients, resulting in weight loss.
    • Depression: While depression can sometimes lead to increased appetite, it can also cause a decrease in appetite, resulting in weight loss.
  • Do Not Miss (Deadly if Missed)
    • Cancer (including lymphoma, leukemia, or other malignancies): Although less common in young adults, certain types of cancer can present with unexplained weight loss.
    • HIV/AIDS: Weight loss is a common symptom in the later stages of HIV infection.
    • Tuberculosis (TB): This infectious disease can cause significant weight loss, especially if left untreated.
    • Addison's disease: A rare disorder of the adrenal glands, Addison's disease can lead to weight loss, among other symptoms, due to the deficiency of cortisol and aldosterone.
  • Rare Diagnoses
    • Pheochromocytoma: A rare tumor of the adrenal gland that can lead to weight loss due to increased metabolism.
    • VIPoma: A rare endocrine tumor that can cause severe diarrhea, leading to weight loss.
    • Whipple's disease: A rare, systemic bacterial infection that can cause weight loss, diarrhea, and other symptoms.

Each of these diagnoses requires careful consideration of the patient's overall clinical presentation, including their medical history, physical examination findings, and laboratory results. A thorough evaluation is essential to determine the underlying cause of weight loss in an 18-year-old and to initiate appropriate treatment.

Related Questions

Is it acceptable to monitor and trim a partially injured toenail with dry blood underneath, rather than removing it, in a patient with no signs of infection or other complications?
Can sensitivity to fiber cause constipation instead of regulating bowels?
What is the most common complication after I&D of a thyroglossal abscess?
What are the implications of removing the distal phalange of the great toe?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question