OBJECT The anterior approach to the lumbar spine may be associated with iliac artery thrombosis. Intraoperative heparin can be administered to prevent thrombosis; however, there is a concern that this will increase the procedural blood loss. The aim of this study was to examine whether intraoperative heparin can be administered without increasing blood loss in anterior lumbar spine surgery. METHODS A prospective study of consecutive anterior approaches for lumbar spine surgery was performed between January 2009 and June 2014 by a single vascular surgeon and a single spine surgeon. Patients underwent an anterior lumbar interbody fusion (ALIF) at L4–5 and/or L5–S1, a total disc replacement (TDR) at L4–5 and/or L5–S1, or a hybrid procedure with a TDR at L4–5 and an ALIF at L5–S1. Heparin was administered intravenously when arterial flow to the lower limbs was interrupted during the procedure. Heparin was usually reversed on removal of the causative retraction. RESULTS The cohort consisted of 188 patients with a mean age of 41.7 years; 96 (51.1%) were male. Eighty-four patients (44.7%) had an ALIF, 57 (30.3%) had a TDR, and 47 (25.0%) had a hybrid operation with a TDR at L4–5 and an ALIF at L5–S1. One hundred thirty-four patients (71.3%) underwent a single-level procedure (26.9% L4–5 and 73.1% L5–S1) and 54 (28.7%) underwent a 2-level procedure (L4–5 and L5–S1). Seventy-two patients (38.3%) received heparinization intraoperatively. Heparin was predominantly administered during hybrid operations (68.1%), 2-level procedures (70.4%), and procedures involving the L4–5 level (80.6%). There were no intraoperative ischemic vascular complications reported in this series. There was 1 postoperative deep venous thrombosis. The overall mean estimated blood loss (EBL) for the heparin group (389.7 ml) was significantly higher than for the nonheparin group (160.5 ml) (p < 0.0001). However, when all variables were analyzed with multiple linear regression, only the prosthesis used and level treated were found to be significant in blood loss (p < 0.05). The highest blood loss occurred in hybrid procedures (448.1 ml), followed by TDR (302.5 ml) and ALIF (99.7 ml). There were statistically significant differences between the EBL during ALIF compared with TDR and hybrid (p < 0.0001), but not between TDR and hybrid. The L4–5 level was associated with significantly higher blood loss (384.9 ml) compared with L5–S1 (111.4 ml) (p < 0.0001). CONCLUSIONS During an anterior exposure for lumbar spine surgery, the administration of heparin does not significantly increase blood loss. The prosthesis used and level treated were found to significantly increase blood loss, with TDR and the L4–5 level having greater blood loss compared with ALIF and L5–S1, respectively. Heparin can be administered safely to help prevent thrombotic intraoperative vascular complications without increasing blood loss.