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Vitamin B1 (Thiamine)

SI UNITS (recommended)

CONVENTIONAL UNITS

(Essential Water-Soluble Vitamin - Required for Energy Metabolism, Nerve Function & Carbohydrate Utilization)

Synonyms

  • Thiamine
  • Vitamin B1
  • Thiamin
  • Thiamine pyrophosphate (TPP) – active form
  • Thiamine diphosphate (ThDP)
  • Thiamine monophosphate (TMP)
  • Anti-beriberi factor

Units of Measurement

  • nmol/L
  • µg/L
  • µg/dL
  • µg/100 mL
  • µg%
  • ng/mL

Unit Conversions

Molecular Weight of Thiamine = 337.27 g/mol

nmol/L ↔ µg/L

1 nmol/L=0.337 µg/L1\ \text{nmol/L} = 0.337\ \text{µg/L}1 nmol/L=0.337 µg/L 1 µg/L=2.97 nmol/L1\ \text{µg/L} = 2.97\ \text{nmol/L}1 µg/L=2.97 nmol/L

µg/dL → µg/L

1 µg/dL=10 µg/L1\ \text{µg/dL} = 10\ \text{µg/L}1 µg/dL=10 µg/L

ng/mL → µg/L

1 ng/mL=1 µg/L1\ \text{ng/mL} = 1\ \text{µg/L}1 ng/mL=1 µg/L

µg/100 mL = µg% = µg/dL

Description

Vitamin B1 (thiamine) is an essential water-soluble vitamin required for:

  • Carbohydrate metabolism
  • Energy production
  • Nervous system function
  • Neuromuscular conduction
  • Cardiac function

The biologically active form is Thiamine Pyrophosphate (TPP), a cofactor required for several mitochondrial enzymes:

  • Pyruvate dehydrogenase
  • Alpha-ketoglutarate dehydrogenase
  • Transketolase (pentose phosphate pathway)

Because thiamine stores are small (2–3 weeks), deficiency can develop rapidly.

Physiological Role

1. Energy Metabolism

Critical for mitochondrial oxidative decarboxylation of carbohydrates.

2. Nervous System Function

Required for:

  • Axonal conduction
  • Myelin integrity
  • Neurotransmitter synthesis

3. Glucose Utilization

Deficiency leads to lactic acidosis due to impaired pyruvate metabolism.

4. Pentose Phosphate Pathway

Transketolase enzyme requires thiamine.

Clinical Significance

DEFICIENCY

Thiamine deficiency → severe and potentially life-threatening disorders.

1. Dry Beriberi

  • Peripheral neuropathy
  • Areflexia
  • Weakness
  • Sensory loss
  • Foot drop/wrist drop

2. Wet Beriberi

  • High-output heart failure
  • Edema
  • Tachycardia
  • Dilated cardiomyopathy

3. Wernicke Encephalopathy

Triad:

  • Ophthalmoplegia/nystagmus
  • Ataxia
  • Confusion

Seen in:

  • Alcohol use disorder
  • Malnutrition
  • Hyperemesis gravidarum
  • Bariatric surgery

4. Korsakoff Syndrome

  • Chronic memory disorder after untreated Wernicke’s

5. Infantile Thiamine Deficiency

  • Heart failure
  • Respiratory distress
  • Stridor

6. At-risk groups

  • Alcoholism
  • Malabsorption
  • Elderly
  • Dialysis patients
  • Refeeding syndrome
  • HIV/AIDS
  • Cancer cachexia

EXCESS

Thiamine is water-soluble; toxicity is extremely uncommon.
Very high parenteral doses may cause:

  • Local reactions
  • Rare anaphylaxis

Reference Intervals

(Tietz 8E + Mayo + ARUP)

Whole Blood Thiamine - Preferred

  • 70 – 180 nmol/L
     (= 24 – 60 µg/L)
    (= 2.4 – 6.0 ng/mL)

Serum Thiamine

  • > 8 µg/L usually adequate (not preferred due to variability)

Erythrocyte Transketolase Activity

Used in specialized centers to assess functional deficiency.

Diagnostic Uses

1. Evaluation of Wernicke-Korsakoff Syndrome

Emergency supplementation required; testing should NOT delay treatment.

2. Diagnosis of Beriberi

Both dry (neurologic) and wet (cardiac).

3. Nutritional Assessment

Part of micronutrient evaluation in malnutrition.

4. Monitoring in Patients at Risk

  • Alcohol use disorder
  • Bariatric surgery
  • Dialysis
  • Hyperemesis gravidarum

5. Refeeding Syndrome

High metabolic demand increases thiamine requirement.

Analytical Notes

  • Whole blood is the most accurate specimen.
  • Protect sample from light.
  • Measured by HPLC or LC-MS/MS.
  • Serum thiamine levels can be misleading since TPP is intracellular.

Clinical Pearls

  • Always give IV thiamine BEFORE glucose in suspected Wernicke’s - glucose can worsen deficiency.
  • Alcoholism is the most common cause of severe deficiency.
  • TPP measurement is far superior to serum thiamine.
  • Thiamine deficiency can cause high lactate due to impaired pyruvate metabolism.
  • Acute deficiency can mimic stroke, sepsis, or heart failure - high suspicion needed.

Interesting Fact

Thiamine was the first vitamin ever discovered (named “thio-amine,” a sulfur-containing amine), leading to the concept of “vitamins” in human nutrition.

References

  1. Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Vitamins
  2. WHO/FAO Micronutrient Guidelines - Thiamine
  3. NIH: Office of Dietary Supplements - Thiamine
  4. Mayo Clinic Laboratories - Thiamine (TPP)
  5. ARUP Consult - Vitamin Testing
  6. MedlinePlus - Thiamine Test

Last updated: January 27, 2026

Reviewed by : Medical Review Board

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