Vitamin B1 (Thiamine): What Your Result Means

What is Vitamin B1 (Thiamine)?

Thiamine (B1) is a cofactor for several enzymes that convert carbohydrates into energy. Because the brain and heart depend heavily on that energy, B1 deficiency hits those organs first. Classic deficiency states include beriberi (heart and nerve symptoms) and Wernicke-Korsakoff syndrome (associated with alcohol misuse). Testing is indicated when those risk factors are present, not routinely.

Typical reference interval: Normal blood thiamine is commonly roughly 70–180 nmol/L (assays vary; some labs measure the enzyme activity instead). Values below the lab's range suggest deficiency, especially in someone with risk factors.. Laboratories differ — the interval printed on YOUR report always governs.

If your Vitamin B1 (Thiamine) is high

Common reasons Vitamin B1 (Thiamine) runs above the reference interval:

• Supplement overuse — B1 supplements — rare, since excess is usually excreted — can raise measured levels
• Recent high-dose therapy — patients on intravenous or prescription thiamine can read high transiently

If your Vitamin B1 (Thiamine) is low

Common reasons Vitamin B1 (Thiamine) runs below the reference interval:

• Alcohol use disorder — by far the most common cause — alcohol blocks absorption and use of thiamine
• Very restricted diet — low-carb, high-refined-food, or impoverished diets can fall short
• Chronic diarrhea or vomiting — nutrient loss through the gut depletes thiamine
• Malabsorption conditions — celiac, Crohn's, or surgical gut changes impair absorption
• Pregnancy and breastfeeding — demand rises in these states
• Severe and prolonged illness — critical illness consumes thiamine faster than intake supplies it

Symptoms worth knowing

Early deficiency shows as fatigue, irritability, and brain fog. More advanced deficiency brings heart symptoms (rapid heartbeat, breathlessness) and nerve symptoms (tingling, weakness) — the classic beriberi picture — plus the confusion and eye-movement problems of Wernicke syndrome in alcohol-related cases.

What usually happens next

1. A low B1 with alcohol use or a restricted diet warrants clinical review — replacement is usually simple and effective
2. Interpret B1 with overall nutrition (other B vitamins, folate) since deficiencies rarely travel alone
3. If you take a multivitamin, mention it — it may already contain thiamine and change the plan

Frequently asked questions about Vitamin B1 (Thiamine) results