Lab marker · Low

Low Vitamin B1 (thiamine): what it means

A Vitamin B1 (thiamine) result below the normal range is considered low. Here is what a reduced Vitamin B1 (thiamine) can point to, and when it is worth discussing with a doctor.

Reference range: ~70–180 nmol/L; deficiency is important in alcohol excess and malnutrition — where it can cause a treatable brain emergency (Wernicke's)

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What a low Vitamin B1 (thiamine) 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.

Conditions this can relate to

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Mediora.AI is informational - interpretation, not a diagnosis. A single out-of-range value is common and often benign; always discuss decisions with your doctor.