Introduction: In India, head and neck cancer is the commonest cancer in men and in both sexes.In most cases, due to extensive loco-regional involvement, poor general condition of the patient, or co-morbid conditions, curative treatment is not possible. Aims & Objectives: To know serum Magnesium levels in patients of head and neck squamous cell carcinoma before and after treatment. Data & Methodology: This study was conducted in the Department of Biochemistry in collaboration with Department of Radiotherapy, Pt BD Sharma Post Graduate Institute of Medical Sciences, Rohtak, India. For the completion of the study, 30 newly diagnosed patients with HNSCC, and 30 age and sex matched healthy individuals were taken. Chi-square and t-test were applied to know the association and comparison between case and control group respectively. Results: The subjects were categorized into three groups such asgroup A- Pretreatment cases, group B- Post-treatment cases and group C- Controls. Plasma glucose in group A was 84.73 ± 2.97 (57-115)mg/dL. Plasma glucose in group B was 103.46±5.15 (61-171) mg/dL whereas group C plasma glucose was 84.73±2.97 (57-115) mg/dL. p value between group A and group B was 0.001. It was found significant difference between cases before and after treatment in glucose levels. The levels in cases before treatment were found significantly different from controls regarding ALT, Albumin, total protein and TBIL with p values 0.015, 0.020 respectivelyConclusions: It was found highly significant difference between case and control groups especially for LDL, Protein and Calcium wise classification respectively.