PurposeThe aim of this study was to analyze the effect of preoperative bicarbonate and lactate levels (LL) on the short-term outcomes and prognosis in elderly (≥ 65 years) patients with colorectal cancer (CRC).MethodsWe collected the information of CRC patients from Jan 2011 to Jan 2020 in a single clinical center. According to the results of preoperative blood gas analysis, we divided patients into the higher/lower bicarbonate group and the higher/lower lactate group, and compared their baseline information, surgery-related information, overall survival (OS) and disease-free survival (DFS).ResultsA total of 1473 patients were included in this study. Comparing the clinical data of the higher/lower bicarbonate group and the higher/lower lactate group, the lower group were older (p < 0.01), had higher rates of coronary heart disease (CHD) (p = 0.025), a higher proportion of colon tumors (p < 0.01), larger tumor size (p < 0.01), higher rates of open surgery (p < 0.01), more intraoperative blood loss (p < 0.01), higher overall complications (p < 0.01) and 30-day deaths (p < 0.01). The higher LL patients had more male patients (p < 0.01), higher body mass index (BMI) (p < 0.01) and drinking rates (p = 0.049), higher rates of type 2 diabetes mellitus (T2DM) (p < 0.01) and lower rates of open surgery (p < 0.01). In multivariate analysis, age (p < 0.01), BMI (p = 0.036), T2DM (p = 0.023), and surgical methods (p < 0.01) were independent risk factors of overall complications. The independent risk factors for OS included age (p < 0.01), tumor site (p = 0.014), tumor stage (p < 0.01), tumor size (p = 0.036), LL (p < 0.01), and overall complications (p < 0.01). The independent risk factors of DFS included age (p = 0.012), tumor site (p = 0.019), tumor stage (p < 0.01), LL (p < 0.01), and overall complications (p < 0.01).ConclusionPreoperative LL significantly affected postoperative OS and DFS of CRC patients, but bicarbonate might not affect the prognosis of CRC patients. Therefore, surgeons should actively focus on and adjust the LL of patients before surgery.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12893-023-02039-x.