Vitamin B1 (thiamine): Optimal Testing Recommendations

  • Whole blood is the preferred specimen for assessment of thiamine status and body storage.

Guidelines for Test Utilization

What does the test tell me?

  • This test is intended to support the identification of thiamine deficiency which may be associated with serious physiological effects that are reversible upon thiamine administration (1).
  • Most of thiamine diphosphate (TDP, the primary active form of Vitamin B1) present in erythrocytes. Development of thiamine deficiency is associated with a rapid drop in TDP in erythrocytes which reflects tissue TDP stores (1).

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When should I order this test?

If clinical symptoms consistent with thiamine deficiency or B vitamin deficiency or those at high risk of deficiency. [back to top]

When should I NOT order this test?

Diagnosis and treatment for thiamine deficiency may be made clinically based upon response to treatment with vitamin B1 supplementation, in which case testing may not be necessary. [back to top]

How should I interpret the result?

Whole blood (or erythrocyte) thiamine levels below the lower limit of the reference interval may support the diagnosis of thiamine deficiency. [back to top]

Is the test result diagnostic/confirmatory of the condition?

Test results that are low may indicate a vitamin B1 deficiency but will not reveal whether it is due to an inadequate supply (i.e. diet) or an inability to absorb or use available B vitamins, for which additional assessment may be required. [back to top]

Are there factors that can affect the lab result?

Non-fasting status and recent thiamine supplementation may impact results.
Samples should be protected from light prior to testing as exposure to light may impact results. [back to top]

Are there considerations for special populations?

Exclusively breastfed infants of thiamine deficient mothers, low thiamine diet (e.g. primarily white rice), alcoholism, dialysis, chronic diarrhea, chronic diseases associated with malabsorption (e.g. celiac disease), HIV/AIDS, post-operative bariatric surgery, high dose diuretics, and parenteral nutrition confer higher risk of vitamin B1 deficiency. [back to top]

What other test(s) might be indicated?

Thiamine deficiency can occur due to inadequate dietary intake, absorption or storage or due to dietary exposure to anti-thiamin factors. Additional lab testing may be required to determine the cause of the deficiency. [back to top]


  1. Lu J, Frank EL. Rapid HPLC measurement of thiamine and its phosphate esters in whole blood. Clin Chem. 2008;54(5):901-906. 
  2. Whitfield KC, Bourassa MW, Adamolekun B, et al. Thiamine deficiency disorders: diagnosis, prevalence, and a roadmap for global control programs. Ann N Y Acad Sci. 2018;1430(1):3-43. 

Last reviewed: March 2023. The content for Optimal Testing: the Association for Diagnostics & Laboratory Medicine’s (ADLM) Guide to Lab Test Utilization has been developed and approved by the Academy of Diagnostics & Laboratory Medicine and ADLM’s Science and Practice Core Committee.

As the fields of laboratory medicine and diagnostic testing continue to grow at an incredible rate, the knowledge and expertise of clinical laboratory professionals is essential to ensure that patients receive the highest quality and most useful laboratory tests. ADLM’s Academy and Science and Practice Core Committee have developed a test utilization resource focusing on commonly misused tests in hospitals and clinics. Improper test utilization can result in poor patient outcomes and waste in the healthcare system. This important resource geared toward medical professionals recommends better tests and diagnostic practices. Always consult your laboratory director to make sure these recommendations are appropriate for your patient population.