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For further information, see CMDT Part 29-08: Thiamine (B1) Deficiency

Key Features

  • Most common cause: chronic alcohol use disorder

  • Other causes

    • Malabsorption (eg, following bariatric surgery)

    • Dialysis

    • Chronic protein-calorie undernutrition

  • Thiamine depletion can be precipitated when patients with low thiamine are given a large carbohydrate load, such as an intravenous dextrose infusion

Clinical Findings

  • Early manifestations

    • Anorexia

    • Muscle cramps

    • Paresthesia

    • Irritability

  • Advanced deficiency chiefly affects cardiovascular system (wet beriberi) or nervous system (dry beriberi)

  • Wet beriberi

    • Occurs with severe physical exertion and high carbohydrate intake

    • Characterized by marked peripheral vasodilation resulting in high-output heart failure with dyspnea, tachycardia, cardiomegaly, pulmonary edema, and peripheral edema with warm extremities

  • Dry beriberi

    • Occurs with inactivity and low-calorie intake

    • Involves both peripheral and central nervous systems

    • Peripheral nerve involvement includes symmetric motor and sensory neuropathy with pain, paresthesia, and loss of reflexes in legs more than the arms

    • Central nervous system involvement includes Wernicke encephalopathy (clinical triad of nystagmus progressing to ophthalmoplegia, truncal ataxia, and confusion) and Korsakoff syndrome (amnesia, confabulation, and impaired learning)


  • Clinical response to empiric thiamine therapy

  • Biochemical tests

    • Measure thiamine directly

    • Erythrocyte transketolase activity and urinary thiamine excretion

    • Transketolase activity coefficient > 15–20% suggest thiamine deficiency


  • Thiamine: 50–100 mg intravenously per day for the first few days, followed by 5–10 mg once daily orally

  • Therapeutic doses of other water-soluble vitamins

  • Treatment results in complete resolution of symptoms and signs in 50% of patients (one-fourth immediately and one-fourth over days); the remaining 50% have only partial resolution or no benefit

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