What could be causing my fatigue?

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Last updated: April 2, 2025View editorial policy

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Differential Diagnosis for Fatigue

The following is a list of potential causes for feeling tired, categorized by likelihood and potential impact.

  • Single most likely diagnosis
    • Anemia or Iron Deficiency: This is a common condition that can cause fatigue due to a lack of red blood cells or hemoglobin, leading to inadequate oxygen delivery to tissues.
  • Other Likely diagnoses
    • Sleep Disorders (e.g., Insomnia, Sleep Apnea): Poor sleep quality or duration can significantly contribute to feelings of tiredness.
    • Depression: A mental health condition that often presents with fatigue, among other symptoms like mood changes and loss of interest in activities.
    • Hypothyroidism: An underactive thyroid gland can lead to fatigue, weight gain, and other symptoms due to a decrease in metabolic rate.
    • Chronic Fatigue Syndrome: A condition characterized by extreme fatigue that cannot be explained by any underlying medical condition.
    • Dehydration: Inadequate fluid intake can lead to feelings of tiredness, headaches, and difficulty concentrating.
  • Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
    • Diabetes: Uncontrolled diabetes can lead to fatigue, among other severe complications like ketoacidosis or hyperosmolar hyperglycemic state.
    • Heart Failure: Reduced cardiac output can cause fatigue, shortness of breath, and other symptoms that can be life-threatening if not addressed.
    • Chronic Obstructive Pulmonary Disease (COPD): A progressive lung disease that can cause fatigue, shortness of breath, and other respiratory symptoms.
    • Adrenal Insufficiency: A condition where the adrenal glands do not produce adequate hormones, leading to fatigue, weight loss, and potentially life-threatening complications.
  • Rare diagnoses
    • Addison's Disease: A rare endocrine disorder where the adrenal glands do not produce enough cortisol and aldosterone, leading to fatigue, weight loss, and other symptoms.
    • Mitochondrial Myopathies: A group of rare genetic disorders that affect the mitochondria, leading to fatigue, muscle weakness, and other systemic symptoms.
    • Sleep Disorders like Narcolepsy: A neurological disorder that affects the brain's ability to regulate sleep-wake cycles, leading to excessive daytime sleepiness and fatigue.

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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