Vitamin B1 (Thiamine Diphosphate) (fingerstick)

Vitamin B1 (thiamine) is needed to convert carbohydrates into energy and for the functioning of nerves, the brain and memory. It is found mainly in bread and grain products, and also in potatoes, meat, milk, legumes and nuts. The test usually measures thiamine diphosphate, the active form, in whole blood. The body has only a small store, so with too little intake or poor absorption over a longer period, a deficiency can develop fairly quickly.

• Vitamin B1 deficiency with excessive alcohol use, malnutrition or an eating disorder
• Deficiency due to poor absorption in diseases of the stomach and intestines
• Rarely: serious consequences of a deficiency, such as beriberi or Wernicke-Korsakoff syndrome

With a low value, the GP looks for the cause, such as alcohol use, diet or a bowel disease, and usually prescribes vitamin B1. With confusion, problems walking or abnormal eye movements in someone with a deficiency, prompt assessment is needed, often in hospital.

A clearly low value fits a deficiency, but the result is always assessed together with symptoms and risk factors. In people without symptoms and with a normal diet, a deficiency is rare; the test is mainly used when there is a specific suspicion, such as with excessive alcohol use or malnutrition. When a severe deficiency is strongly suspected, vitamin B1 is often given without waiting for the result.

• Supplements and multivitamins raise the value; a tablet shortly before the blood draw gives too favorable a picture.
• The sample must be kept chilled or frozen; with transport that takes too long or is too warm, the result can be unreliable.
• Reference values differ between laboratories and measurement methods.

A vitamin B1 deficiency is rare in healthy people in the Netherlands, because bread and grain products provide a lot of thiamine. A deficiency occurs mainly in people with excessive alcohol or drug use and with diseases of the digestive tract. According to the Netherlands Nutrition Centre (Voedingscentrum), beriberi no longer occurs in the Netherlands; how often a milder deficiency occurs is not well known.

Useful when a deficiency is suspected in risk groups, such as excessive alcohol use, malnutrition or an eating disorder and diseases of the stomach or intestines, together with symptoms that fit it. In healthy people without symptoms and with a normal diet, the result says little: a deficiency is then rare and tiredness usually has another cause.

• In people without symptoms and with a normal diet, the test rarely yields anything; a slightly abnormal value can cause unnecessary worry or unnecessary follow-up testing.

• NVKC, allesovertesten.nl: Vitamine B1
• Voedingscentrum: Vitamine B1 (thiamine)
• UMC Utrecht, Bepalingenwijzer: Vitamine B1 in bloed