• The new method for calculating hidden blood loss in TLIF yields significantly higher estimates than traditional methods (284.24 mL vs. 165.77 mL, P<0.05), accounting for 58.6% of total blood loss.
• Hidden blood loss is positively correlated with the number of surgical segments and operation time, and negatively correlated with platelet count.
• Decreased platelet count is an independent risk factor for hidden blood loss in TLIF.
• The new method provides a more accurate assessment of perioperative blood loss, highlighting the clinical importance of hidden blood loss in TLIF.