General
Vitamin B1 test
Lab test

Vitamin B1 test

Recommended for people at risk of thiamine deficiency — including those with significant alcohol use, malabsorption conditions, prolonged vomiting, or very limited diets — and for anyone with neurological symptoms that may reflect a nutritional cause. Fasting recommended. Results reviewed by a General Medicine clinician.

Receive actionable insights and deep analysis—not just lab values– in as little as 48 hours

Clear guidance, and follow-up care available

Simple, online scheduling for labs and everything else

Most insurance accepted

Board-certified

No hidden fees

Available nationwide

What is a Vitamin B1 Test?

The Vitamin B1 test measures thiamine — an essential B vitamin the body cannot produce on its own and must obtain through diet. Thiamine is required for converting carbohydrates into energy and is critical for nerve and brain function. Deficiency can develop rapidly in high-risk individuals and causes serious neurological and cardiovascular complications if not identified and treated promptly.

Thiamine deficiency detection

Identifies low thiamine levels before clinical deficiency progresses — particularly important in people with alcohol use disorder, malabsorption conditions, prolonged vomiting, or severely restricted diets, where deficiency can develop quickly and cause irreversible neurological damage.

Neurological and cardiovascular symptom evaluation

Thiamine deficiency causes peripheral neuropathy, confusion, and in severe cases, Wernicke's encephalopathy (a neurological emergency) or wet beriberi (heart failure). Testing provides the objective confirmation needed to initiate appropriate thiamine replacement before symptoms worsen.

Supplementation effectiveness

Confirms whether thiamine supplementation is adequately restoring blood levels — particularly important for people with impaired absorption where standard oral doses may be insufficient and higher doses or IV administration may be required.

Complete insights in as little as 48 hours

1

Book your test

Instantly schedule at 2,000+ labs nationwide, at a time that works for you. Most visits take 15 minutes or less, with both walk-ins and appointments available.

2

Get results in 48 hours

Your results are delivered quickly—and reviewed by medical professionals. You’ll get clear explanations, robust health insights, and recommended next steps tailored to your health needs.

3

Take action with physician guidance

Choose to review your results and manage your plan with a General Medicine physician—or simply use the insights on your own.

4

Track progress over time

Repeat annually to see trends, improvements, and new emerging risks or book individual tests that focus on your set goals

All your care in one place. That’s the General Medicine difference.

We help you understand your options, connect you to the right clinicians, manage prescriptions, coordinate any needed evaluations, and keep an eye on your overall health along the way. It’s comprehensive care that looks at the full picture — your goals, your history, your lifestyle — and makes it simple to move forward with confidence.

Your care plan
Clinician

What's included

Test type

Blood sample

Collection method

Venipuncture

Fasting

Not required

Results processing time

4 to 6 days

Vitamin B1 (Thiamine)

A vital nutrient your body uses to transform food into energy. Low levels can lead to fatigue, weakness, or nerve problems.

Virtual visit with clinician

Ongoing support, always available.

You’ll be supported by experienced clinicians who care for a wide range of health needs, from everyday concerns to more complex conditions.

Our clinicians track your progress over time and adjust your care as needed. If medication is prescribed, we’ll manage dosing and monitor for side effects. If lab testing is recommended, we review results and refine your plan accordingly. You’re never left to navigate care on your own.

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Frequently asked questions

What does a Vitamin B1 (thiamine) test measure?

The Vitamin B1 test measures thiamine levels in the blood — essential for energy metabolism, nerve function, and brain health. Thiamine deficiency causes a range of neurological and cardiovascular complications, from peripheral neuropathy to serious conditions like Wernicke's encephalopathy.

Do I need to fast before a thiamine test?

Fasting for 6–8 hours is generally recommended for the most accurate thiamine level, as recent food intake can transiently affect results. Morning testing after an overnight fast is ideal.

Who is most at risk for thiamine deficiency?

Heavy alcohol users are at highest risk, as alcohol both reduces thiamine absorption and depletes stores. Other high-risk groups include people with malabsorption conditions (Crohn's, celiac, bariatric surgery), prolonged vomiting (hyperemesis gravidarum), those on long-term diuretics, and people with very poor dietary intake.

What symptoms suggest thiamine deficiency?

Peripheral neuropathy (tingling, numbness, weakness in hands and feet), fatigue, memory problems, confusion, and in advanced cases, heart failure (wet beriberi) or brain damage (Wernicke's) can indicate deficiency. Neurological symptoms warrant prompt evaluation.

If I take a B-complex supplement, do I still need to test?

Supplementation doesn't guarantee adequate tissue levels, particularly if absorption is impaired. Testing is the only way to confirm whether your supplementation is effective, and it's especially important for people with known risk factors rather than assuming supplements are sufficient.
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