Vitamin B1 (thiamine)
A vitamin essential for turning food into energy and for the nervous system. Deficiency is uncommon on a good diet but important in alcohol excess and malnutrition, where it can cause heart failure or a treatable brain emergency (Wernicke's) — so it must not be missed.
What it measures
Vitamin B1 (thiamine) is essential for converting carbohydrates into energy and for the normal working of nerves and the heart. The body stores relatively little, so deficiency can develop within weeks when intake is poor or needs are high. In well-nourished populations it is uncommon, but there are important high-risk groups: people with alcohol dependence (poor diet plus impaired absorption and use), severe malnutrition, prolonged vomiting (including severe pregnancy sickness), after bariatric surgery, and in critical illness. Deficiency causes 'beriberi' — a form affecting the heart (heart failure and fluid retention) and a form affecting the nerves (numbness, weakness). Most critically, in people who abuse alcohol or are malnourished, thiamine deficiency can cause Wernicke's encephalopathy — a brain emergency with confusion, unsteadiness and eye-movement problems that can become permanent (Korsakoff's) if not treated. A vital safety point is that giving glucose to a thiamine-deficient person can precipitate this, so at-risk people are given thiamine first.
What a high value can mean
- Supplementation — the usual reason for a high level; thiamine is water-soluble and excess is generally not harmful.
What a low value can mean
- Alcohol dependence — the most important cause; poor intake plus impaired absorption and use.
- Malnutrition or prolonged vomiting — including severe pregnancy sickness (hyperemesis).
- After bariatric surgery, or in critical illness.
- Effects — heart failure and fluid retention (wet beriberi), nerve damage (dry beriberi), and Wernicke's encephalopathy (confusion, unsteadiness, eye-movement problems).
When to discuss with a doctor
Thiamine deficiency is important not because it is common but because it is dangerous and completely treatable. It should be considered — and treatment often given without waiting for the test — in anyone at risk (alcohol dependence, malnutrition, persistent vomiting, after bariatric surgery) who develops confusion, unsteadiness, eye-movement problems, unexplained heart failure or nerve symptoms. Wernicke's encephalopathy is a medical emergency treated with urgent thiamine. A crucial safety rule is that glucose should not be given to an at-risk person before thiamine, as it can trigger the condition. Mediora.AI can flag the context and related nutrient deficiencies, but suspected thiamine deficiency in an at-risk person is treated promptly by a doctor, often before the level returns.