Thiamine

Vitamin B1

Vitamins & Minerals

What is Vitamin B1?

Vitamin B1, also known as thiamine, is a water-soluble vitamin that serves as an essential coenzyme in carbohydrate metabolism, energy production, and neural function. Thiamine pyrophosphate (TPP), the biologically active form, is required by key enzymes in the citric acid cycle and the pentose phosphate pathway—metabolic processes that generate ATP (cellular energy) and provide building blocks for DNA and RNA synthesis. The body stores only small amounts of thiamine (approximately 25–30 mg total), with the highest concentrations found in skeletal muscle, heart, liver, kidneys, and brain.

Because thiamine cannot be synthesized by the body and has a relatively short half-life of 9–18 days, regular dietary intake is essential. Rich dietary sources include whole grains, pork, legumes, nuts, and fortified cereals. Thiamine levels in blood are typically measured as whole blood thiamine or erythrocyte transketolase activity, which reflects functional thiamine status. Thiamine deficiency, while relatively uncommon in developed nations due to food fortification, remains a significant clinical concern in chronic alcohol use disorder, bariatric surgery patients, and populations relying heavily on polished rice.

Why It Matters

Thiamine is indispensable for converting food into usable energy. Deficiency causes two classic syndromes: beriberi (affecting the cardiovascular and peripheral nervous systems) and Wernicke-Korsakoff syndrome (a potentially fatal neurological emergency most commonly seen in chronic alcoholism). Wet beriberi causes heart failure with edema, while dry beriberi causes peripheral neuropathy and muscle wasting. Wernicke encephalopathy—characterized by confusion, ataxia, and eye movement abnormalities—is a medical emergency that requires immediate intravenous thiamine. Early detection and treatment of thiamine deficiency can prevent permanent brain damage.

Normal Reference Ranges

GroupRangeUnit
Adults (whole blood thiamine diphosphate)70–180nmol/L

Reference ranges may vary by laboratory. Always compare results to the ranges provided by your testing facility.

What High Thiamine Levels Mean

Common Causes

  • High-dose thiamine supplementation
  • Excessive fortified food intake
  • Rare—water-soluble vitamin readily excreted by kidneys

Possible Symptoms

  • Generally no adverse effects—excess is excreted in urine
  • Very rare reports of allergic reactions with parenteral administration

What to do: High thiamine levels are generally not a clinical concern, as excess thiamine is efficiently excreted by the kidneys. No known toxicity has been established for oral thiamine, even at very high doses. Reduce supplementation if levels are significantly above normal, but no specific treatment is typically needed.

What Low Thiamine Levels Mean

Common Causes

  • Chronic alcohol use (impairs absorption and increases excretion)
  • Malnutrition or restricted diets
  • Bariatric surgery or GI surgery
  • Prolonged vomiting (hyperemesis gravidarum)
  • Chronic diarrhea or malabsorption
  • High-dose diuretic use (increases urinary losses)
  • Refeeding syndrome in malnourished patients
  • Diets high in polished (white) rice

Possible Symptoms

  • Fatigue, irritability, and poor concentration
  • Peripheral neuropathy (tingling, numbness in extremities)
  • Muscle weakness and wasting
  • Rapid heart rate and edema (wet beriberi)
  • Confusion, ataxia, and eye abnormalities (Wernicke encephalopathy)
  • Memory loss and confabulation (Korsakoff syndrome)
  • Anorexia and weight loss

What to do: Mild deficiency is treated with oral thiamine supplementation, typically 50–100 mg daily. Suspected Wernicke encephalopathy is a medical emergency requiring immediate high-dose intravenous thiamine (200–500 mg three times daily) before glucose administration—giving glucose without thiamine can precipitate or worsen the condition. Address underlying causes such as alcohol cessation, improved nutrition, and treatment of malabsorption. Hospitalized patients at risk should receive prophylactic thiamine.

When Is Thiamine Testing Recommended?

  • In patients with chronic alcohol use disorder
  • Before and after bariatric surgery
  • When neurological symptoms of unknown cause are present
  • In cases of unexplained heart failure or peripheral neuropathy
  • In malnourished or critically ill patients
  • When prolonged vomiting or malabsorption is present

Frequently Asked Questions

Alcohol impairs thiamine at multiple levels: it reduces dietary intake (poor nutrition), decreases intestinal absorption, impairs liver activation of thiamine to its active form, and increases urinary excretion. This multi-hit mechanism makes chronic alcohol users extremely vulnerable to deficiency. Wernicke encephalopathy develops in 30–80% of affected individuals and can progress to permanent Korsakoff syndrome (irreversible memory loss and confabulation) if not treated promptly with parenteral thiamine.
Refeeding syndrome is a potentially fatal condition that occurs when malnourished patients are given food or intravenous nutrition too rapidly. As the body shifts from fat to carbohydrate metabolism, demand for thiamine (needed for carbohydrate processing) surges, rapidly depleting already low stores. This can precipitate acute thiamine deficiency, lactic acidosis, and cardiac failure. Prophylactic thiamine supplementation is essential before initiating nutrition in starved patients.
Yes, thiamine is heat-sensitive and water-soluble, making it particularly vulnerable to cooking losses. Boiling can destroy 20–60% of thiamine content, especially if cooking water is discarded. Baking, roasting, and prolonged cooking at high temperatures also reduce thiamine. Microwaving and steaming preserve more thiamine than boiling. Additionally, sulfites (used as food preservatives) and baking soda destroy thiamine. For maximum retention, cook foods briefly in minimal water and consume the cooking liquid when possible.

Related Biomarkers

PLPVitamin B6B12Vitamin B12FolateFolateMgMagnesium

Want your Thiamine levels analyzed?

Upload your lab results for an instant AI-powered breakdown of all your biomarkers.

Upload Lab Results →

Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Reference ranges may vary between laboratories. Always consult your healthcare provider for interpretation of your specific test results.

Disclaimer: SymptomGPT is not a medical diagnosis tool and does not provide medical advice. Always consult a qualified healthcare professional. If you are experiencing a medical emergency, call 911 immediately.