Vitamins & Nutrients Updated Apr 17, 2026

Vitamin B1 (Thiamine) (B1)

Vitamin B1 (Thiamine) (B1) is a laboratory value that reports the amount of thiamine measured in blood, usually as part of a Vitamins & Nutrients panel. On a lab report or blood test, B1 helps show whether the measured level is within the Vitamin B1 (Thiamine) normal range and how the result compares with the lab’s reference range.

What Is Vitamin B1 (Thiamine) (B1)?

Vitamin B1 (Thiamine) (B1) is a blood test value that measures thiamine, a vitamin found in the bloodstream and inside cells. B1 on a blood test reflects how much of this nutrient is available in circulating blood at the time of collection. Vitamin B1 (Thiamine) on a lab report is usually listed as a concentration or activity-based value rather than a count. It is often reviewed as part of a broader Vitamins & Nutrients panel.

Why Is Vitamin B1 (Thiamine) (B1) Tested?

B1 is commonly measured in a Vitamins & Nutrients panel and may also appear in broader nutrition-focused blood testing. Vitamin B1 (Thiamine) on a lab report is used to document the body’s thiamine status alongside other nutrient markers. The B1 test helps show whether the measured value fits the lab’s Vitamin B1 (Thiamine) normal range. It adds context when comparing nutrition-related values across multiple blood test results.

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Vitamin B1 (Thiamine) (B1) Normal Range

Group Range Unit
Adult Male 70–180 nmol/L
Adult Female 70–180 nmol/L

Reference ranges may vary by laboratory and individual factors.

What Does High B1 Mean?

High B1 means the measured Vitamin B1 (Thiamine) level is above the lab’s Vitamin B1 (Thiamine) reference range, often due to more thiamine in blood than expected or reduced plasma volume concentrating the sample. In many labs, a high B1 test result may be considered above the upper limit of the reference interval, but the exact threshold depends on the method and units used. High B1 on a blood test can reflect recent intake, supplements, or sample-related concentration effects. The meaning is read together with the full Vitamin B1 (Thiamine) on a lab report result, not in isolation.

Associated factors

Recent supplement use — a B1 test can read high after recent thiamine intake because circulating levels rise after exposure.
Fortified foods — higher intake from enriched foods can raise the measured Vitamin B1 (Thiamine) test result.
Dehydration — lower plasma volume can concentrate B1 in the sample and make the value look higher.
Recent exercise — temporary fluid shifts can change how concentrated the blood sample appears.
Altitude exposure — changes in plasma volume can affect measured concentration on a Vitamin B1 (Thiamine) blood test.
Pregnancy-related plasma changes — shifts in blood volume can alter the apparent B1 level.
Timing after a meal — a recent meal or supplement can raise a short-term B1 result.
Medication effects — some medicines and infusions can change measured B1 values or interfere with the assay.
Lab method variation — different platforms may report slightly different high B1 thresholds and values.
Natural day-to-day variation — a B1 test can vary modestly from one draw to the next.

What Does Low B1 Mean?

Low B1 means the measured Vitamin B1 (Thiamine) level is below the lab’s Vitamin B1 (Thiamine) reference range, often reflecting less thiamine available in circulating blood. A low B1 test result may be reported below the lower limit of the lab’s range, but the exact cutoff depends on the method, specimen type, and units. Low B1 on a blood test can occur when intake is low, absorption is limited, or losses are higher than usual. The result is best interpreted as part of the full Vitamin B1 (Thiamine) on a lab report pattern rather than as a standalone number.

Associated factors

Low dietary intake — fewer thiamine-rich foods can lower the B1 test result over time.
Malabsorption — reduced absorption in the gut can lead to low B1 in blood.
Frequent alcohol use — this can reduce intake, absorption, and storage of thiamine.
GI fluid loss or poor intake — limited nutrient intake can make Vitamin B1 (Thiamine) levels fall.
Increased energy demand — periods of high metabolic demand can use more thiamine.
Diuretic use — some medicines can increase loss of water-soluble vitamins in urine.
Dialysis or filtration treatments — water-soluble nutrients may be lost during treatment.
Refeeding after low intake — levels can shift quickly as the body uses available B1.
Sample handling delay — delays in processing can affect a Vitamin B1 (Thiamine) blood test result.
Natural variation — a low B1 value can sometimes reflect normal day-to-day fluctuation near the cutoff.

How Vitamin B1 (Thiamine) (B1) Relates to Other Values

Vitamin B1 (Thiamine) is often reviewed with other nutrition markers in the same panel, such as vitamin B12, folate, vitamin B6, and vitamin D. If the panel also includes ferritin, iron, MCV, MCH, hematocrit (Hct), or red blood cell count (RBC), the pattern helps describe overall blood composition and nutrient status. For example, B1 plus MCV can help show whether red blood cells are larger or smaller than typical. B1 plus Hct and RBC helps place the result in the context of overall red cell mass and concentration. On a lab report, the B1 test is usually most useful when read together with these related markers, not alone.

What Factors Affect Vitamin B1 (Thiamine) (B1) Levels?

Age can affect B1 values because nutrient handling and intake patterns change over time. Sex and body size may create small differences in the Vitamin B1 (Thiamine) normal range used by some labs. Hydration, recent exercise, and altitude can shift concentration-based B1 results by changing plasma volume. Diet, supplement use, and time since the last dose can have a direct effect on B1 on a blood test. Lab method also matters, since different assays may use different calibration and reference intervals for the Vitamin B1 (Thiamine) reference range.

How It Is Tested

Vitamin B1 (Thiamine) is measured from a blood draw, usually from a vein in the arm. The lab measures thiamine directly or by a related analytical method, depending on the platform. Results are commonly reported in ng/mL, nmol/L, or as an activity-based unit, depending on the lab.

How to Prepare

No fasting is usually required for a Vitamin B1 (Thiamine) test, but the lab’s collection instructions may differ. Because supplements can affect B1, the timing of recent intake may matter for the reported result.

Frequently Asked Questions

What is the normal range for Vitamin B1 (Thiamine)?
The normal range for Vitamin B1 (Thiamine) depends on the lab method and the unit used, but many references use about 70 to 180 nmol/L for a B1 blood test. Some labs report slightly different Vitamin B1 (Thiamine) normal range values, so the lab’s own reference range is the key comparison. On a lab report, the number is interpreted against that stated range, not against one universal cutoff.
What does B1 stand for?
B1 stands for Vitamin B1 (Thiamine). In a blood test or lab report, B1 is the shorthand label for the thiamine measurement. It is used in nutrition-focused testing and in Vitamin B1 (Thiamine) lab entries.
What does a high Vitamin B1 (Thiamine) mean on a lab report?
A high Vitamin B1 (Thiamine) result means the B1 test is above the lab’s reference range. This often reflects recent intake, supplement use, or a concentrated sample from lower plasma volume. The exact meaning depends on the lab’s method, the unit, and the full test context.
What does a low Vitamin B1 (Thiamine) mean on a lab report?
A low Vitamin B1 (Thiamine) result means the measured B1 level is below the lab’s reference range. This can reflect low intake, reduced absorption, higher loss, or sample handling effects. On a lab report, the result is compared with the lab’s Vitamin B1 (Thiamine) normal range.
Can diet affect Vitamin B1 (Thiamine)?
Yes. Diet can affect B1 because Vitamin B1 (Thiamine) comes from food and supplements, so recent intake can move the number up or down on a blood test. A B1 test can change after fortified foods or supplement use, especially if the sample is taken soon after intake.
What is the difference between Vitamin B1 (Thiamine) and vitamin B12?
Vitamin B1 (Thiamine) and vitamin B12 are different nutrients measured for different reasons. B1 reflects thiamine status, while B12 reflects a separate vitamin involved in other blood and nerve-related processes. On a panel, they are read as separate values with separate reference ranges.
What unit is Vitamin B1 (Thiamine) measured in?
Vitamin B1 (Thiamine) is commonly measured in nmol/L, ng/mL, or sometimes by an activity-based unit depending on the lab. The unit appears next to the B1 result on the lab report. The reported Vitamin B1 (Thiamine) reference range must match the same unit.
How much can Vitamin B1 (Thiamine) change between tests?
B1 can change by a small to moderate amount between tests because intake, hydration, and lab method can shift the number. A Vitamin B1 (Thiamine) test result taken after supplements or a different collection condition may not match the earlier value exactly. Minor changes near the reference range are common.
Is Vitamin B1 (Thiamine) different for men and women?
Many labs use the same B1 reference range for adult men and women, such as 70 to 180 nmol/L. Some laboratories may set slightly different cutoffs based on method or population data. The lab report’s listed Vitamin B1 (Thiamine) normal range is the best comparison.
Why is Vitamin B1 (Thiamine) tested in a Vitamins & Nutrients panel?
Vitamin B1 (Thiamine) is tested in a Vitamins & Nutrients panel to show thiamine status alongside other nutrient markers. The B1 test helps provide a broader picture of nutritional balance and blood composition. It is most useful when reviewed with the other values in the same panel.
What does B1 mean on a blood test?
B1 on a blood test means the lab measured Vitamin B1 (Thiamine). The result is compared with the lab’s Vitamin B1 (Thiamine) normal range to see whether it is within the expected interval. The label does not stand alone; it is interpreted with the unit and reference range on the report.

Disclaimer

This content is for informational and educational purposes only. It is not intended as medical advice, diagnosis, or treatment recommendation. Reference ranges may vary by laboratory. Always discuss your results with a qualified healthcare professional.

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