Objective: Appropriate selection of the type of blood specimen tube employed is of great importance to the accurate and reliable measurement of oxidative stress biomarkers. This study examined the effect of specimen variety on measurement results using serum and plasma samples obtained from blood tubes with six different contents for measuring ischemia-modified albumin (IMA), total oxidant status (TOS), and total antioxidant status (TAS). Materials and Methods: Ischemia-modified albumin, TOS, and TAS levels were assayed in serum and plasma specimens obtained from blood collected from 16 volunteers and placed into serum collection tubes, plain tubes, and anticoagulant tubes containing dipotassium EDTA, trisodium citrate, lithium heparin, and sodium fluoride/disodium EDTA (NaF/Na2EDTA). IMA was measured using the Bar-Or method, and TOS and TAS were measured using TOS and TAS assay kits, respectively. Total albumin assay was performed using a Beckman Coulter AU5800 autoanalyzer. Results: In all tubes, IMA, IMA/albumin ratio, TOS, TAS, and oxidative stress index values were compared, and all these parameters were found to be statistically significant between six different tubes (p=0.0001). Ischemia-modified albumin and TOS measurements in plasma specimens obtained from tubes containing dipotassium EDTA and NaF/Na2EDTA differed significantly from the results of the other specimens. Conclusion: We conclude that IMA and TOS cannot be measured from blood specimens with dipotassium EDTA and NaF/ Na2EDTA. However, TAS can be determined in all specimen types. The selection of the specimen type to be used in the measurement of IMA, TOS, and TAS is of great importance and now requires standardization.