Background: Evidence shows direct link of HER2 to increased glycolysis and over production of lactate dehydrogenase (LDH). HER2 overexpression, high LDH and low glucose pleural levels are associated with poor prognosis in lung cancer. Here, their relationships were investigated. Materials and Methods: HER2 positivity was studied using immunohistochemistry in non-small cell lung cancer. Glucose and LDH levels were measured using commercial colorimetric kits. Results: Of 42 patients (29 adenocarcinoma and 13 squamous cell carcinoma), 28 (66.7%) were HER2-negative, 14 (33.3%) were HER2- positive, including 9 (21.4%) weakly stained (1+) and 5 (11.9%) moderately stained (2+) samples. The relationship between HER2 and glucose and LDH levels were tested in 20 newly diagnosed lung cancer patients who had simultaneous pleural and serum samples. Pleural and serum LDH levels were increased, and pleural glucose levels were decreased with the scale of HER2 positivity, and that the difference in glucose levels between HER2-negative group and HER2-positive patients scored at 2+ reached statistical significance (p=0.02). This latter group all had pleural glucose levels below 40 mg/dl. Conclusions: For the first time, we showed a significant association between low pleural glucose level and overexpression of HER2 in lung cancer. Further investigations are warranted to disclose the association of HER2 with low pleural glucose levels in other populations, with a larger sample size, in malignant pleural effusions caused by other types of cancer, and finally to assess employment as a screening tool for finding HER2-positive cases of lung cancer.