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Last updated: October 14, 2025View editorial policy

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Differential Diagnosis for Weight Decrease

  • Single most likely diagnosis
    • Malnutrition: This is often the most straightforward reason for weight loss, especially if the decrease in weight is significant and occurs over a short period. It can be due to inadequate dietary intake or an increased demand for nutrients that the body cannot meet.
  • Other Likely diagnoses
    • Diabetes Mellitus: Uncontrolled diabetes can lead to weight loss due to the body's inability to use glucose as an energy source, leading to the breakdown of fat for energy.
    • Hyperthyroidism: An overactive thyroid gland can increase metabolism, leading to weight loss despite increased appetite.
    • Chronic Infections (e.g., Tuberculosis): Chronic infections can cause weight loss due to increased metabolic rate, decreased appetite, and malabsorption.
    • Cancer: Certain types of cancer, especially those affecting the digestive system, can lead to weight loss due to decreased appetite, malabsorption, and increased metabolic demand.
  • Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
    • HIV/AIDS: Weight loss is a common symptom, especially in the later stages of the disease, due to malabsorption, chronic infections, and increased metabolic rate.
    • Addison's Disease: This rare endocrine disorder can cause weight loss, among other symptoms like fatigue and low blood pressure, due to the adrenal glands not producing enough cortisol and aldosterone.
    • Pernicious Anemia: Although more commonly associated with neurological symptoms, severe cases can lead to significant weight loss due to malabsorption of vitamin B12.
  • Rare diagnoses
    • Celiac Disease: An autoimmune disorder that causes the immune system to react to gluten, leading to malabsorption and potential weight loss if not managed properly.
    • Whipple's Disease: A rare bacterial infection that affects the digestive system, leading to malabsorption and weight loss.
    • Amyloidosis: A condition characterized by the deposition of abnormal proteins (amyloid) in various tissues, which can lead to weight loss among other systemic symptoms.

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.

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