Breast cancer is the most common malignancy worldwide. The expression of microRNA (miRNA/miR)-146 has been shown to be related to breast cancer progression, and its expression in breast cancer cells has been investigated in the blood of patients. In the present study, the concentration of lipid peroxidation in blood cells was measured by detecting the level of malondialdehyde (MDA) to explore the level of oxidative cellular damage in the collected blood samples of breast cancer patients, alongside healthy women used as the controls. Reverse transcription-quantitative PCR was used to analyze the expression of miR-146 in the blood of both breast cancer patients and healthy controls. As regards miR-146 expression, the fold change in expression in patients with breast cancer was 3.1-fold higher than that in healthy women. The findings revealed that the expression of miR-146 in patients with breast cancer was almost 3-fold higher than that in healthy women. Notably, the levels of MDA, which has been employed as a marker of lipid peroxidation, were significantly higher in patients with breast cancer (3.25±0.22) compared with healthy women (0.99±0.099). On the whole, the findings of the present study indicate that both miR-146 expression and MDA levels may function as potential biomarkers for determining susceptibility to breast cancer.