What Is Thiamine Deficiency?

  • Afsheen Hidayat MSc in Clinical Microbiology, Queen Mary University of London, UK

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Thiamine deficiency is a condition that occurs when your body doesn't get enough thiamine. Thiamine, also known as vitamin B1, is an essential nutrient that is required by your body to help it function well by turning food into energy and keeping the nervous system healthy. Thiamine deficiency is a serious condition that can lead to a wide range of symptoms, from fatigue and muscle weakness to severe complications such as heart damage and permanent nerve damage.


Thiamine, also known as vitamin B1, is a nutrient that plays a critical role in maintaining overall health and is one of the eight essential B vitamins. It is essential in helping the body convert food (carbohydrates) into energy (glucose) and several basic cell functions. Thiamine also plays a role in the transmission of nerve signals (enabling messages to be sent between your brain and the other parts of your body)  and in nerve regeneration. 

The body’s total reserve stores of thiamine are relatively small. Hence, thiamine deficiency can occur in individuals as a result of poor nutrition, alcohol use problems, increased urine excretion, and acute metabolic stress. 1 The body does not produce thiamine and it must be consumed continuously because it is a water-soluble vitamin that cannot be stored in the body for an extended time.  Whole grains, yeasts, meats (particularly pork), beans, and nuts are the food types that contain the most thiamine 2. The symptoms of thiamine deficiency start to emerge when thiamine levels are exhausted which usually takes about four weeks after stopping intake.

Causes of thiamine deficiency

Deficiency of thiamine can be related to:3

  • Inadequate dietary intake of thiamine resulting from:
    • Diets high in polished rice or processed grains
    • Parenteral nutrition (the feeding of nutritional products to a person directly intravenously) without adequate thiamine supplementation.
  • Increased thiamine required by the body:
  • Increased loss of thiamine:
    • Diarrhoea
    • Hyperemesis gravidarum (excessive vomiting during pregnancy)
    • Use of diuretic medication- long-term use of medications like diuretics can interfere with thiamine absorption and contribute to deficiency.

Signs and symptoms of thiamine deficiency

Thiamine deficiency can manifest in various ways, affecting multiple body systems. Early signs of thiamine deficiency include fatigue, muscle weakness, and irritability. The symptoms can be subtle or severe, depending on the extent of the deficiency. Some common symptoms include: 

  • Fatigue: Fatigue and weakness are early signs of thiamine deficiency due to its role in energy production.
  • Muscle weakness: Thiamine deficiency can lead to muscle weakness and pain, making routine activities challenging.
  • Cardiovascular issues: Thiamine deficiency can affect the heart, leading to heart palpitations, rapid heartbeat, and, in severe cases, heart failure.
  • Neurological symptoms: One of the hallmark features of thiamine deficiency is its impact on the nervous system. Symptoms can include confusion, memory problems, difficulty concentrating, and even hallucinations. 
  • Gastrointestinal disturbances: Individuals with thiamine deficiency may experience nausea, vomiting, and abdominal discomfort.
  • Beriberi: Beriberi is a condition that can result from severe thiamine deficiency, with symptoms including muscle wasting, loss of sensation in the limbs, and difficulty walking. The term "beriberi" refers to a group of disorders caused by thiamine deficiency. There are two main types of beriberi:
    • Wet beriberi occurs when the cardiovascular system is involved. The heart fails to function, leading to poor circulation and oedema (a build-up of fluid in bodily tissues). Wet beriberi presents as cardiac failure and difficulty in breathing. Wet beriberi is a medical emergency and, without treatment, can lead to death within days. Thiamine supplementation can slowly help with recovery, but most patients require supportive care in an ICU setting.
  • Dry beriberi occurs when the central nervous system is involved and is usually caused by poor intake of thiamine. It causes disruption to motor functioning (the movement of the muscles) and impaired reflexes. Symptoms can also include difficulty walking and numbness in the hands or feet. Wernicke-Korsakoff syndrome is the name for a variant of beriberi that affects the brain and primarily affects adults with chronic alcoholism. This illness manifests in well-defined stages, commencing with nausea and vomiting and progressing to horizontal nystagmus (involuntary side-to-side movement of the eyes), vision problems, fever, movement difficulty, and progressive mental decline before developing into the Korsakoff syndrome, a chronic memory disorder. Less than half of patients significantly improve after treatment. Only patients who have not progressed to Korsakoff syndrome can improve. Infants with thiamine deficiency have heart failure as their predominant problem.4 

Diagnosis of thiamine deficiency

Thiamine deficiency is diagnosed using a physical examination and laboratory testing:

  • Medical history: A key diagnostic factor for thiamine deficiency is the presence of risk factors. The healthcare provider will ask about dietary habits, alcohol consumption, and any underlying medical conditions.
  • Physical examination: Thiamine deficiency is diagnosed based on symptoms and the findings of a physical assessment, with a focus on the heart and nervous system.
  • Laboratory tests: There are no simple tests to confirm the diagnosis of thiamine deficiency. Electrolyte levels (levels of salts and minerals in the blood) are typically measured by blood testing to rule out other potential causes. Blood tests can also assess an individual’s thiamine status.
    • Blood thiamine levels: Blood tests can measure thiamine levels in the bloodstream. Low levels of thiamine are indicative of deficiency.
    • Transketolase activity assay: This functional test measures the activity of an enzyme that depends on thiamine. Reduced activity indicates a decrease in thiamine in the body. 
    • Imaging studies: In the presence of neurological symptoms, MRI scanning can be used to see changes consistent with a diagnosis of Wernicke-Korsakoff syndrome and assess brain damage.

A diagnosis of thiamine deficiency is mostly confirmed by the resolution of symptoms with thiamine supplements.

Treatment and management

Thiamine stores in the body can be kept at an adequate level by eating a diet high in thiamine-containing foods. Communities in highly industrialised nations with reliable access to food rarely experience nutritional deficits. Thiamine replacement should be given when a thiamine deficiency is diagnosed or suspected. 

  • Thiamine supplementation: Thiamine is often administered intravenously or intramuscularly in two doses of 100 mg each: the first dose and the daily dose. Cardiac symptoms resolve within a few days or hours, whereas nerve symptoms improve over the course of three to six months, with motor symptoms improving faster than sensory symptoms. Most people see some recovery, but this usually happens slowly, and in those with severe nerve damage, there can be persistent disabilities. Thiamine deficiency is easily curable, and most indications and symptoms completely disappear with thiamine supplementation, therefore the prognosis for patients with the condition is often positive.5
  • Dietary improvement by encouraging consumption of thiamine-rich foods. Some of the best places to find thiamine include foods like:
    • Enriched white rice or egg noodles
    • Fortified breakfast cereal
    • Pork
    • Trout
    • Black beans
    • Sunflower seeds
    • Acorn 
    • Squash
    • Yoghurt
    • Many commercial bread varieties
    • Corn
  • Monitoring and follow-up: Patients diagnosed with thiamine deficiency will need regular follow-up appointments to monitor their progress and ensure that thiamine levels remain adequate.

Prevention of thiamine deficiency

Prevention is a key aspect of the management of thiamine deficiency. Thiamine deficiency can be prevented by:

  • Eating a balanced diet: A diet containing a variety of thiamine-rich foods such as whole grains, lean meats, fish, beans, and nuts.
  • Avoiding excessive alcohol consumption: Limit alcohol intake to reduce the risk of thiamine deficiency, as alcohol can interfere with thiamine absorption.
  • Management of underlying health conditions: conditions that affect the absorption of thiamine, such as celiac disease or Crohn's disease, should be managed appropriately.
  • Supplementing when necessary: In cases where dietary intake may be insufficient, thiamine supplements are recommended by a healthcare professional.


Thiamine deficiency is the underlying cause of several clinical syndromes, such as Wernicke's encephalopathy, wet beriberi, and dry beriberi. The clinical manifestation is based on how persistent the deficit is. Alcoholism, malabsorption, and a diet low in thiamine are the main risk factors for thiamine deficiency. Due to the non-specific nature of signs and symptoms, diagnosis is suspected in the presence of risk factors. If vitamin B1 deficiency is suspected, treatment should start right away because there is no quick diagnostic test for the illness. Wernicke's encephalopathy, a brain injury resulting from severe vitamin B1 deficiency, can necessitate institutional care or result in death. With prompt diagnosis and appropriate treatment, most individuals can recover from thiamine deficiency and prevent its recurrence through dietary adjustments and a healthy lifestyle.


  1. Attaluri P, Castillo A, Edriss H, Nugent K. Thiamine deficiency: an important consideration in critically ill patients. The American Journal of the Medical Sciences [Internet]. 2018 Oct 1 [cited 2023 Aug 31];356(4):382–90. Available from: https://www.sciencedirect.com/science/article/pii/S0002962918302271
  2. Whitfield KC, Bourassa MW, Adamolekun B, Bergeron G, Bettendorff L, Brown KH, et al. Thiamine deficiency disorders: diagnosis, prevalence, and a roadmap for global control programs. Ann NY Acad Sci [Internet]. 2018 Oct [cited 2023 Aug 31];1430(1):3–43. Available from: https://onlinelibrary.wiley.com/doi/10.1111/nyas.13919
  3. Wiley KD, Gupta M. Vitamin b1 (Thiamine) deficiency. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Aug 31]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK537204/
  4. Smith TJ, Johnson CR, Koshy R, Hess SY, Qureshi UA, Mynak ML, et al. Thiamine deficiency disorders: a clinical perspective. Ann N Y Acad Sci [Internet]. 2021 Aug [cited 2023 Aug 31];1498(1):9–28. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8451766/
  5. Hammond N, Wang Y, Dimachkie M, Barohn R. Nutritional neuropathies. Neurol Clin [Internet]. 2013 May [cited 2023 Sep 1];31(2):477–89. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4199287/

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Afsheen Hidayat

M.B.B.S, MSc in Clinical Microbiology

Afsheen possesses a strong background in both the medical and scientific disciplines and is a highly educated health researcher. She is a medical expert who is eager to pursue a career in clinical research and medical writing because she believes that it is crucial to improve patient outcomes and provide better medical care. After working as a clinician in Dubai, she came to realise that her goal was to use her extensive research skills to raise the standard of healthcare. She obtained an MSc in Clinical Microbiology from Queen Mary University of London to advance her research career, and she is currently working as a medical writer.

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