Vitamin B1 (Thiamine) · low result
What does a low Vitamin B1 (Thiamine) mean?
Short answer
Low thiamine (vitamin B1) is most common with alcohol use disorder, after bariatric surgery, with persistent vomiting (including pregnancy), diuretic use in heart failure, dialysis, and diets built on refined carbohydrates. Deficiency affects the nerves and the heart — tingling and weakness, and in severe cases confusion and heart failure (beriberi, Wernicke's). It responds quickly to repletion, so a low result is acted on rather than watched.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
When does this result need same-day care?
- Confusion, unsteady walking or abnormal eye movements, especially with alcohol use — emergency care (Wernicke's encephalopathy)
What is the normal range for Vitamin B1 (Thiamine)?
- age 18+: 70.0 – 180 nmol/L
Can reflect alcohol use, malnutrition, or absorption issues. Severe deficiency causes beriberi.
Full reference table, citations and testing options: Vitamin B1 (Thiamine) biomarker page.
What are the common causes of low Vitamin B1 (Thiamine)?
- Alcohol use disorder
- Bariatric surgery, malabsorption, prolonged vomiting or diarrhea
- Loop diuretics (furosemide) in heart failure
- Dialysis, HIV, hyperthyroidism, critical illness
- Diets high in refined carbohydrates and low in whole grains, legumes and pork
- Refeeding after starvation
What symptoms go with low Vitamin B1 (Thiamine)?
- Tingling, numbness and weakness in the legs, poor balance
- Fatigue, irritability, poor memory
- Swelling, breathlessness, fast heart rate (wet beriberi); confusion and eye-movement problems (Wernicke's) — emergencies
What do clinicians usually check next?
- Clinician review — deficiency with neurological or cardiac symptoms is treated urgently, before repeat testing
- Magnesium (needed for thiamine to work), B12, folate
- Address the cause: alcohol, absorption, diuretics
Follow-up tests available at TestWell: Magnesium ($19.99), Folate (Vitamin B9) ($32.99).
How do you recheck Vitamin B1 (Thiamine)?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Vitamin B1 (Thiamine) | Test | $43.99 | Yes | 5–10 business days |
Common questions
Which is better, blood thiamine or the erythrocyte transketolase test?
Whole-blood or red-cell thiamine diphosphate (what most labs report) is now the standard; transketolase activity is an older functional test used in some centers.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.