Vitamin B1 (Thiamine) levels: what's normal, high and low
A B vitamin essential for energy metabolism and nerve function.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
The short answer
Vitamin B1 (Thiamine) is measured with a standard blood draw after an 8–12 hour fast. A typical reference range is 70.0 – 180 nmol/L. At TestWell it's $43.99 all-in as Vitamin B1 (Thiamine), results in 5–10 business days, drawn at Quest or Labcorp. An out-of-range result is a prompt to look closer, not a diagnosis.
- Units
- nmol/L
- Sample
- Blood draw
- Fasting
- 8–12 hours
- Results
- 5–10 business days
- Price
- $43.99
- Labs
- Quest or Labcorp
Vitamin B1 (Thiamine) Reference Range
These are the typical adult reference ranges used by major US labs. Your report will include the specific range used by the lab that processed your sample.
| Population | Range |
|---|---|
| age 18+ | 70.0 – 180 nmol/L |
Reference ranges are educational. Always interpret your result with the specific range printed on your lab report and discuss anything outside the range with a clinician.
Have a result in hand? analyze it with your AI assistant using these reviewed ranges, or run it through our explainer. Tools: look up another marker's range · convert lab units
What your Vitamin B1 (Thiamine) result may mean
Can reflect alcohol use, malnutrition, or absorption issues. Severe deficiency causes beriberi.
What a low Vitamin B1 (Thiamine) means: causes, symptoms, next steps ↓Educational only — not a diagnosis. Many factors can influence a single result. Discuss anything that concerns you with a healthcare provider.
What does a low Vitamin B1 (Thiamine) mean?
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.
Common causes of a 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
Ordered from most to least common.
Symptoms that can go with it
- 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 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 at TestWell: Magnesium ($19.99), Folate (Vitamin B9) ($32.99).
Seek care promptly if
- Confusion, unsteady walking or abnormal eye movements, especially with alcohol use — emergency care (Wernicke's encephalopathy)
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 only — not a diagnosis. A single result outside the range is a prompt to look closer with a clinician.
How do you get a Vitamin B1 (Thiamine) test?
Order online, a licensed physician reviews the requisition, and you walk into a nearby lab for the draw. Vitamin B1 (Thiamine) is available on its own or inside these panels — panels cost less per marker when you want the fuller picture.
| Option | Includes | Price |
|---|---|---|
| Vitamin B1 (Thiamine) | This marker only | $43.99 |
Quest vs. Labcorp for Vitamin B1 (Thiamine): which lab should you pick?
Both are CLIA-certified national labs and the result is clinically equivalent, so pick whichever location is closer. Your report will print that lab's own reference range, which can differ slightly from the table above.
| Lab | Available | Price |
|---|---|---|
| Quest Diagnostics | Yes | $43.99 |
| Labcorp | Yes | $43.99 |
| BioReference (NY & NJ) | No | — |
Need help choosing a location? Use the lab finder to see draw sites near your ZIP.
Related Vitamins & Nutrients biomarkers
Markers commonly tested alongside Vitamin B1 (Thiamine).
Frequently asked
What does a low Vitamin B1 (Thiamine) mean?
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.
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.
Do I need a doctor's order to test my vitamin b1 (thiamine)?
No. TestWell's licensed physician network reviews and approves your order — usually within minutes. You can place an order online without an in-person visit or a referral from your own doctor.
How long does it take to get Vitamin B1 (Thiamine) results?
Most Vitamin B1 (Thiamine) results are available in 1–3 business days after your specimen arrives at the lab. You'll get an email the moment your results are ready, with everything viewable in your TestWell portal.
How much does a Vitamin B1 (Thiamine) test cost?
Our Vitamin B1 (Thiamine) starts at $43.99. That's the all-in price — no copays, no insurance hoops, no surprise bills. HSA and FSA cards are accepted.
Do I need to fast before my Vitamin B1 (Thiamine) test?
Yes — for the most accurate result, fast for 8–12 hours before your blood draw. Water is fine; coffee, food, and supplements are not. Your prep instructions will be included with your order.
Which lab will process my Vitamin B1 (Thiamine) test?
Your test will be processed by Quest Diagnostics, Labcorp, or BioReference depending on which is closest to you and which lab carries the test. All three are CLIA-certified and trusted by hospitals nationwide. You'll choose your lab during checkout from 4,000+ locations.
Ready to test your vitamin b1 (thiamine)?
Order in two minutes, get physician-approved, and visit a lab the same day. Starts at $43.99.