Background: Kidney function test (KFT) is a routine laboratory examination used in the diagnosis of many disorders, the kidney participates in several essential functions in the human body, and kidney dysfunction can lead to morbidity and mortality. Therefore, studying the levels of KFT in early diagnosed cancer patients can identify how the kidney perform when cancer begins, and which parameter of KFT is affected early. Objective: This study aimed to evaluate levels of kidneys function profile including blood urea, creatinine, sodium (Na), potassium (K), and chloride in untreated cancer patients. Patients and methods: 211 participants including 44 healthy controls and 167 patients diagnosed as early cancer were enrolled in this study in Taif city, and this study was performed at King Faisal Hospital (KFH) and Taif University. Serum levels of blood urea, creatinine, sodium (Na), potassium (K), and chloride were analyzed. The total number of patients was 167 and healthy controls were 44. Types of cancer in the patients included in this study were 49 breast cancer, 45 gastrointestinal tract cancer, 39 gynecological tumors, 17 head and neck cancer and 17 respiratory cancer. Statistical assessment was done by applying T-test, Chi-square, odds ratio. Results: Sodium, potassium, creatinine and chloride levels were significantly higher in cancer patients compared to the healthy controls and the urea was normal and nothing was significant. Conclusion: Most common electrolytes abnormality increased in our study group of cancer patients. A sudden death could be resulted when the potassium level increased rapidly. Dysregulation in urea, chloride and creatinine could be a cancer marker and lead to fatal problems.