Vitamin B1 (Thiamine)

Vitamin B1 (thiamine) is a water-soluble vitamin that the body cannot store in meaningful amounts, so a steady supply is essential for normal nerve and muscle function. This test measures the level of thiamine in a simple blood sample to help identify deficiency, which can present with symptoms such as numbness or tingling in the hands and feet, muscle weakness, fatigue, confusion, irritability and, in severe cases, memory problems or heart failure.

It is particularly useful for people with risk factors for low thiamine, including heavy or long-term alcohol use, malabsorption conditions such as coeliac disease or Crohn's disease, bariatric surgery, prolonged vomiting or poor dietary intake, and those taking long-term diuretics. It is also used to monitor people receiving thiamine supplementation or those with chronic conditions that increase thiamine requirements, such as diabetes or thyroid disease.

The test is performed using a simple blood sample, and results are interpreted by your doctor alongside your symptoms, medical history and any other relevant investigations.

Why it matters
Thiamine deficiency is treatable, but if left unrecognised it can lead to irreversible nerve damage and serious cardiac complications. Measuring vitamin B1 gives you and your clinician a clear, objective picture of your thiamine status, so that any shortfall can be corrected early and the underlying cause addressed.