Thiamine deficiency doesn't announce itself dramatically. It tends to creep in as fatigue, irritability, or a vague mental fog — symptoms easy to dismiss or misattribute. Yet a 2024 cross-sectional study published in the Western Journal of Emergency Medicine found that 20.5% of emergency department patients, averaging 57 years of age, had thiamine deficiency, and many had no history of alcohol use disorder. One in five. That's not a rare nutritional curiosity; it's a gap in awareness with real clinical consequences.
The reason it gets missed is partly biological. Your body stores only small amounts of thiamine in the liver, which means a daily intake from food or supplementation isn't optional — it's how you stay topped up. Miss it consistently, and the effects accumulate across multiple systems before most people connect the dots.
Understanding what vitamin B1 actually does, where to find it, and who's at genuine risk of falling short is worth the time, whether you're feeling off and can't explain why, or simply want a clearer picture of a nutrient that does more than most people realise.
Thiamine is a water-soluble B-complex vitamin, which means your body doesn't stockpile it the way it does fat-soluble vitamins like A or D. According to Harvard T.H. Chan School of Public Health's Nutrition Source, thiamine plays a vital role in the growth and function of various cells. Its most fundamental job is enabling energy metabolism: it helps convert carbohydrates into usable fuel and is essential to the biochemical processes that power your cells, particularly in the nervous system and heart muscle.
Nerve cells are especially dependent on thiamine because the brain runs almost entirely on glucose, and glucose metabolism can't function properly without it. This is why deficiency tends to surface first as neurological symptoms. Peripheral nerves, which carry signals between your brain and the rest of your body, are also affected — one of the classic presentations of prolonged deficiency is peripheral neuropathy, a condition involving numbness, tingling, or weakness in the hands and feet. The cardiovascular and musculoskeletal systems are also implicated, which explains why a single nutrient shortfall can produce such a wide and apparently unrelated set of symptoms.
Clinicians use the term "thiamine deficiency disorders" (TDDs) to describe the full range of presentations, from mild and reversible to severe and life-threatening. A comprehensive clinical review on thiamine deficiency disorders found that TDDs affect the metabolic, neurologic, cardiovascular, respiratory, gastrointestinal, and musculoskeletal systems. Critically, the authors note that TDDs are frequently misdiagnosed with fatal consequences or permanent neurological damage — a sober reminder that what looks like burnout or digestive trouble can occasionally be something more serious.
At the severe end sits Wernicke-Korsakoff syndrome, a neurological emergency most commonly associated with long-term heavy alcohol use, though not limited to it. Wernicke encephalopathy (the acute phase) involves confusion, abnormal eye movements, and loss of muscle coordination. Left untreated or treated too late, it can progress to Korsakoff psychosis, a chronic and largely irreversible memory disorder. Beriberi, the other well-known presentation of thiamine deficiency, comes in two main forms: "wet" beriberi primarily affects the cardiovascular system, causing fluid retention and heart failure, while "dry" beriberi primarily affects the nervous system. According to NIH StatPearls, thiamine is FDA-approved for treating Wernicke encephalopathy, infantile beriberi, and cardiovascular disease resulting from deficiency — conditions where prompt correction is essential.
Alcohol use disorder is the most widely known risk factor, because alcohol both reduces thiamine absorption in the gut and impairs the body's ability to store and activate it. But the 2024 emergency department study is a useful corrective here: it found deficiency associated with advanced age, female gender, and leukopenia — low white blood cell count, which can indicate underlying illness or malnutrition. Growing evidence points to thiamine deficiency occurring during acute illness even without any history of alcohol use.
Other groups with elevated risk include people with conditions that impair nutrient absorption, such as Crohn's disease or following bariatric surgery, as well as people on prolonged intravenous nutrition without adequate vitamin supplementation. Older adults are more vulnerable for several reasons: reduced dietary variety, impaired absorption, and a higher burden of chronic illness that increases metabolic demand. Diabetes is another context worth flagging: the NIH Office of Dietary Supplements notes research investigating the relationship between thiamine and diabetes, given that high blood glucose can increase urinary thiamine excretion. People on diets very high in refined carbohydrates and low in whole foods are also at higher risk, as refined grains are stripped of the thiamine naturally present in the bran.
NIH StatPearls identifies the richest dietary sources of thiamine as brown rice, whole grains, pork, poultry, soybeans, nuts, peas, and dried beans. For most people eating a varied diet that includes these foods regularly, meeting daily requirements through food alone is achievable. Fortified foods, including many breakfast cereals and some breads, also contribute meaningfully to intake, particularly in populations where whole grain consumption is lower.
A few practical points worth knowing. Thiamine is water-soluble and heat-sensitive, so cooking methods matter more than with some other vitamins. Boiling vegetables or grains in large amounts of water and discarding that water removes a significant portion of the thiamine content. Steaming or using cooking water in soups and sauces preserves more of it. White rice, which is a dietary staple across much of East Asia including Hong Kong, has the bran and germ removed during milling, which is where most of the thiamine sits. Many commercially sold white rice products are enriched with thiamine after milling, but the amounts vary, and rinsing rice before cooking washes some of that fortification away. For people whose diet relies heavily on white rice and limited protein diversity, intake can be lower than it might appear.
For most adults eating a reasonably varied diet, thiamine supplementation isn't necessary. Where it becomes relevant is in the risk groups described above, or when a clinician identifies low thiamine through blood testing. As Harvard's Nutrition Source explains, because the liver stores only small amounts, regular dietary intake is what maintains adequate levels — which means recovery from deficiency through food alone can be slow, and supplementation or clinical treatment is often used to correct a significant shortfall more reliably.
In clinical settings, doses used to treat deficiency are considerably higher than what's found in standard multivitamins. The NIH Office of Dietary Supplements fact sheet notes that the European Federation of Neurological Societies recommends 200 mg of thiamine intravenously three times daily for Wernicke encephalopathy — a stark contrast to the roughly 1 to 1.4 mg daily intake recommended for most adults to maintain normal levels. This difference underlines an important point: supplementing for general wellbeing and treating a clinical deficiency are two different things, requiring different approaches.
Over-the-counter B1 supplements in Hong Kong are widely available and carry a low risk of toxicity, since excess water-soluble vitamins are excreted in urine rather than stored. That said, self-supplementing as a substitute for investigating persistent symptoms is not the same as getting an accurate picture of what's happening. Blood thiamine levels can be measured, and if you have symptoms that could point to deficiency, a proper assessment gives you far more useful information than guesswork.
Early thiamine deficiency produces non-specific symptoms that are easy to attribute to stress, poor sleep, or a busy lifestyle. Fatigue, reduced concentration, mild irritability, and loss of appetite are common early signs. As deficiency deepens, neurological symptoms become more pronounced: numbness or tingling in the extremities, difficulty walking steadily, and muscle weakness. Cardiovascular symptoms, including an abnormally fast heart rate and shortness of breath, can indicate the wet beriberi presentation affecting the heart.
Because thiamine deficiency disorders are frequently misdiagnosed, the key is not to self-diagnose but to take persistent or unexplained symptoms seriously enough to have them properly investigated. If you fall into a higher-risk group — older adult, restricted diet, recent serious illness, significant alcohol use, or a condition affecting gut absorption — it's worth raising thiamine levels with whoever manages your general health, rather than waiting until symptoms are severe.
Nutritional deficiencies like this one sit at the intersection of several specialities. A general practitioner is the natural first point of contact: they can order blood tests, assess your overall picture, and refer you on if needed. Dietitians are well placed to review dietary patterns in detail and identify gaps that aren't obvious from a standard consultation. If neurological symptoms are present, a neurologist may be involved in assessment and management.
In Hong Kong, access to all of these practitioners exists across public and private settings. If you're unsure where to start or want to compare the types of practitioners available, you can browse specialisations and find practitioners on Healwith.