Thiamine is a water-soluble vitamin of the B complex whose phosphate derivatives are involved in many cellular processes required for overall human health. Thiamine deficiency, often the result of impaired nutritional status associated with chronic diseases from alcoholism to HIV-AIDS, is monitored in patient whole blood samples by HPLC. This certified solution standard is suitable for use as a starting material in preparation of linearity standards, calibrators, and controls in a variety of testing applications from diagnostic testing of thiamine deficiency by HPLC to quality control testing of thiamine-based dietary supplements, fortified foods or pharmaceutical preparations.