What are the symptoms of Thiamine (Vitamin B1) deficiency?

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Last updated: May 11, 2025View editorial policy

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From the Guidelines

Thiamine deficiency symptoms primarily affect the nervous system, cardiovascular system, and gastrointestinal tract, and can range from mild manifestations such as fatigue and irritability to severe symptoms like Wernicke-Korsakoff syndrome and heart failure. According to the most recent and highest quality study 1, thiamine deficiency is a major public health concern and can present with a range of clinical signs and symptoms involving the neurological, psychiatric, and cardiovascular systems. Early signs of thiamine deficiency include mental changes such as apathy, decrease in short-term memory, confusion, and irritability, while more severe manifestations can develop into cognitive deficits, Wernicke-Korsakoff encephalopathy, optic neuropathy, and central pontine myelinolysis 1.

Some key symptoms of thiamine deficiency include:

  • Ataxia, confusion, and coma (Cerebral Beri Beri and Wernicke's encephalopathy) 1
  • Neuropathy and neuritis, especially in lower limbs (Dry Beri Beri) 1
  • Cardiac insufficiency with tachycardia and respiratory symptoms (Wet Beri Beri) 1
  • Peripheral neuropathy, muscle weakness, and unsteady gait 1
  • Enlarged heart, rapid heartbeat, and potential heart failure with shortness of breath and swelling in the lower extremities 1

It is essential to recognize thiamine deficiency early and initiate therapy immediately, as thiamine reserves can be depleted as early as 20 days of inadequate oral intake 1. Treatment requires thiamine supplementation, and intravenous thiamine is necessary for emergency situations like Wernicke's encephalopathy. Thiamine deficiency is common in individuals with risk factors such as alcohol abuse, malabsorption conditions, persistent vomiting, and those on highly processed diets 1.

From the FDA Drug Label

CLINICAL PHARMACOLOGY: ... Increased levels of pyruvic acid in the blood indicate vitamin B 1 deficiency. ... Body depletion of vitamin B 1 can occur after approximately three weeks of total absence of thiamine in the diet.

The symptoms of thiamine deficiency are indicated by increased levels of pyruvic acid in the blood. Key points about thiamine deficiency include:

  • Vitamin B1 deficiency can be detected by increased pyruvic acid levels
  • Body depletion of thiamine can occur after approximately three weeks without thiamine in the diet 2

From the Research

Thiamine Deficiency Symptoms

Thiamine deficiency can manifest in various ways, including:

  • Dry beriberi, which presents with neuropathy 3
  • Wet beriberi, which presents with heart failure, with or without neuropathy 3
  • Wernicke's encephalopathy, a severe thiamine deficiency that can cause encephalopathy, ophthalmoplegia, and ataxia 3, 4, 5
  • Wernicke-Korsakoff syndrome, a condition that can cause memory disturbance, confusion, and other neurological symptoms 4, 6, 7
  • Beriberi, which can manifest in cardiovascular collapse 5

Clinical Presentations

Thiamine deficiency disorders (TDDs) can affect various systems, including:

  • Metabolic system 6
  • Neurologic system 3, 4, 5, 6, 7
  • Cardiovascular system 3, 5
  • Respiratory system 6
  • Gastrointestinal system 6
  • Musculoskeletal system 6

Diagnosis and Treatment

Diagnosis of thiamine deficiency is often clinical, with a low threshold of suspicion and early therapeutic thiamine administration being the best approach 6, 7

  • Treatment with thiamine can lead to rapid clinical improvement, even in severe cases 3, 5, 6
  • Parenteral thiamine administration is recommended, especially in patients with severe deficiency or those who are unable to absorb thiamine orally 4, 5, 7

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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