Written by Charles Gumbley, BHSc (Clinical Nutrition), DipHSc (Western Herbal Medicine)
Evidence checked: 20 July 2026
This article provides general nutrition education. New confusion, abnormal eye movements, severe unsteadiness or difficulty walking can indicate Wernicke encephalopathy and needs immediate medical care. Do not rely on an oral supplement or delay emergency assessment.
Conflict disclosure: Nutrition Market sells supplements. No product is ranked or linked in this guide. The adaptive feed is suppressed until a current product passes every label, dose, intended-population, stock, cost and margin check.
Vitamin B1, also known as thiamine, is a water-soluble vitamin needed for energy metabolism and normal brain, nerve and heart function. Its active form, thiamine diphosphate, acts as a cofactor for enzymes that process glucose, amino acids and fats. The established benefits of vitamin B1 come from getting enough thiamine and correcting deficiency, not from assuming that a high-dose tablet gives extra energy or cognitive function to everyone.
Thiamine deficiency is uncommon in the general Australian population, partly because thiamine is added to bread-making flour. It still occurs in high-risk situations and can become a medical emergency. Heavy alcohol use, severe malnutrition, prolonged vomiting, bariatric surgery, dialysis and some serious illnesses can reduce intake, absorption or storage, or increase requirements.
Key points
- Thiamine helps enzymes convert nutrients from food into energy that cells can use.
- The body stores only a small amount, so regular dietary intake matters.
- Early deficiency can cause fatigue, reduced appetite, muscle weakness, tingling and memory change.
- Severe deficiency can lead to dry or wet beriberi and Wernicke-Korsakoff syndrome.
- Correcting a deficiency is clinically important; routine high-dose use has not been shown to improve diabetes, heart failure or dementia in everyone.
- Suspected Wernicke encephalopathy requires urgent clinician-directed thiamine, usually by injection, rather than a retail product.
Role of Thiamine in Energy and the Nervous System
Thiamine or thiamin refers to the same B vitamin. After absorption, the body converts it into thiamine diphosphate, sometimes called thiamine pyrophosphate. This form of thiamin supports five enzymes involved in glucose metabolism, amino-acid breakdown and links between carbohydrate, protein and fat metabolism.
These pathways include pyruvate dehydrogenase, which helps move carbon from carbohydrate metabolism into the citric-acid cycle, and transketolase in the pentose-phosphate pathway. This is how thiamine contributes to energy production. It does not act as a stimulant and does not create energy independently of food, oxygen and the rest of metabolism.
The nervous system has a high and continuous energy demand. Adequate vitamin B1 supports normal nerve signalling, axonal function and brain-cell metabolism. Thiamine also contributes to normal cardiac-muscle metabolism. Those physiological roles do not establish that B1 supplements enhance mood, memory, athletic performance or overall health when vitamin B1 levels are already adequate.
Vitamin B1 Deficiency and Symptoms of Thiamine Deficiency
Early symptoms of thiamine deficiency can be non-specific: fatigue, weakness, reduced appetite, weight loss, irritability, poor short-term memory, numbness or tingling. These symptoms have many possible causes, so B1 levels are not diagnosed from a checklist alone.
More advanced deficiency can cause dry beriberi, which mainly affects peripheral nerves and muscles, or wet beriberi, which can cause fluid retention and heart failure. Wernicke encephalopathy affects the brain. Its features may include confusion, abnormal or jerky eye movements, double vision, drooping eyelids, poor balance and difficulty walking. Not everyone has the classic combination.
Untreated Wernicke encephalopathy can progress to Korsakoff syndrome with severe memory loss and lasting cognitive impairment. Thiamine deficiency can lead to serious health consequences even before a routine test confirms it. Clinicians may begin urgent treatment when suspicion is high because delay can cause permanent injury.
Assessment considers symptoms, food intake, alcohol use, vomiting, weight change, surgery, medicines and illness. A simple blood thiamine level is not always a reliable measure of tissue status. Tests such as whole-blood thiamine diphosphate or erythrocyte transketolase may be used in specialist settings, but urgent care should not wait for a result when Wernicke encephalopathy is suspected.
Who Has a Higher Risk of Thiamine Deficiency?
People with alcohol dependence are at particular risk because intake, absorption, liver storage and use of thiamine can all be affected. Abruptly stopping heavy alcohol use can also be dangerous. Medical withdrawal support includes assessment for thiamine deficiency and other complications.
Risk is also higher after bariatric surgery, with prolonged vomiting or diarrhoea, hyperemesis gravidarum, severe food restriction, malabsorption, dialysis, HIV/AIDS, cancer therapy or critical illness. Older adults may have low intake, multiple illnesses or medicines that change nutrition. A loop diuretic may increase urinary loss in some people, but medicine changes require a prescriber.
People with diabetes can have lower measured thiamine markers. A 2023 systematic review and meta-analysis found an association, but the clinical meaning remains uncertain. A separate review and meta-analysis of six small trials found no significant improvement in HbA1c, fasting glucose or post-meal glucose from thiamine or benfotiamine. Lower thiamine levels therefore do not make a B1 product a diabetes therapy.
An updated 2024 meta-analysis found that thiamine supplementation corrected deficiency in people with chronic heart failure but did not significantly improve ejection fraction, walking distance, biomarkers or symptom class overall. Thiamine in Alzheimer’s disease has also been studied, but evidence is insufficient for a cognitive-treatment claim. These findings separate correction of deficiency from use for another diagnosis.
Sources of Vitamin B1 and Thiamine-Rich Foods
Sources of vitamin B1 include pork, fish, legumes, nuts, seeds, whole grains and fortified breads or breakfast cereals. In Australia, bread-making wheat flour is fortified with thiamine, with limited exemptions. Processing and prolonged cooking can reduce the amount of thiamine because it is water-soluble and heat sensitive.
Incorporating thiamine-rich foods into your diet can be as simple as choosing wholegrain or fortified bread, beans or lentils, seeds and an appropriate animal or plant protein. Read labels because not all imported, gluten-free or specialty products are fortified in the same way.
Australian Nutrient Reference Values list an adult RDI of 1.2 mg a day for men and 1.1 mg for women, with different life-stage values. These are population reference amounts, not a dosage for suspected deficiency, alcohol withdrawal, prolonged vomiting or post-bariatric care. Energy needs and clinical circumstances can alter requirements.
Thiamine Supplement, Dosage and Safety
A thiamine supplement may be recommended for an identified dietary gap or a defined high-risk situation. The form, route, amount and duration depend on the reason. Oral thiamine, hospital injections and derivatives such as benfotiamine are not interchangeable, and evidence for one form or indication should not be transferred to another.
The National Institutes of Health has not set a tolerable upper limit because adverse effects from high thiamin intakes have not been well documented. That absence is not proof that any dose is useful or risk-free. High-dose products can create false reassurance, duplicate a vitamin B complex or delay investigation of fatigue, neuropathy, vomiting or confusion.
Rare hypersensitivity reactions are more relevant to injected thiamine and require clinical monitoring. Oral products may cause gastrointestinal symptoms in some people. Ask a pharmacist or doctor before taking thiamine supplements during pregnancy, breastfeeding, cancer therapy, dialysis or alongside multiple medicines.
In a person at risk of Wernicke encephalopathy, carbohydrate or glucose can increase thiamine demand. Current NSW Health guidance directs clinicians to give thiamine before glucose when possible, but emergency glucose should never be withheld by a bystander. This is a hospital protocol, not a home-dosing instruction.
Vitamin B1 Benefits Questions
Can I take vitamin B1 every day?
Vitamin B1 comes from foods every day, and a clinician may recommend daily supplementation for a defined reason. Whether a product is appropriate depends on its amount, your diet, risk factors and other supplements. A high-strength tablet is not automatically suitable for routine use.
What are the symptoms of low B1?
Possible symptoms include fatigue, reduced appetite, weakness, tingling, numbness and memory change. Confusion, abnormal eye movements, severe balance problems or difficulty walking need immediate medical assessment because they can indicate Wernicke encephalopathy.
What are 10 benefits of vitamin B1?
It is more accurate to describe ten established roles or deficiency-related contexts than ten universal supplement benefits: thiamine supports pyruvate metabolism, the citric-acid cycle, the pentose-phosphate pathway, branched-chain amino-acid metabolism, normal cellular energy availability, brain metabolism, nerve function, heart-muscle metabolism, normal growth and cell function, and protection from beriberi when intake is adequate. Getting more vitamin B1 than needed has not been shown to multiply these functions.
Who needs vitamin B1 the most?
Everyone needs dietary thiamine, but urgent or targeted supplementation is most relevant to people with suspected deficiency or high-risk states such as heavy alcohol use, severe malnutrition, prolonged vomiting, bariatric surgery or certain serious illnesses. The route and dosage require clinical assessment.
Sources
- Healthdirect Australia. Vitamin B deficiency. Accessed 20 July 2026.
- Healthdirect Australia. Wernicke encephalopathy. Accessed 20 July 2026.
- National Health and Medical Research Council. Nutrient Reference Values: Thiamin. Accessed 20 July 2026.
- NSW Health. Management of Withdrawal from Alcohol and Other Drugs Handbook. 2026; accessed 20 July 2026.
- National Institutes of Health Office of Dietary Supplements. Thiamin: fact sheet for health professionals. Accessed 20 July 2026.
- Muley A, et al. Effect of thiamine supplementation on glycaemic outcomes in adults with type 2 diabetes. BMJ Open. 2022;12:e059834. doi:10.1136/bmjopen-2021-059834.
- He S, et al. Role of thiamine supplementation in chronic heart failure. Clinical Cardiology. 2024;47:e24309. doi:10.1002/clc.24309.
Charles Gumbley founded Nutrition Market to make evidence-informed supplement guidance more accessible. He writes about supplement evidence and product selection for Nutrition Market. Site content is educational and not individual clinical advice.
