Background — Most malignancy patients that undergo radiotherapy with or without chemotherapy, especially those with malignancy of the pelvic region, are accompanied by hypoalbuminemia and kidney injury. Human albumin has been shown to have nephroprotective effects. Snakehead fish extract, a consumable source of albumin, can be an effective and cheap alternative to reduce the risk of kidney injury in malignancy patients. Objective — Analyze the effect of snakehead fish extract on urea, creatinine, and albumin serum levels in radiotherapy patients. Material and Methods — This study was conducted on patients undergoing radiotherapy. They were divided into two groups, each consisting of 15 patients; the control group was given a placebo and the experimental group was given snakehead fish extract. Albumin, urea, and creatinine serum levels were determined respectively by the bromocresol green method, urease method, and jaffe method, both before and after treatment. All data were analyzed using SPSS 22.0. Results — The serum albumin level decreased in both groups. While it dropped further in the treatment group than in the control group, the difference was not significant. Urea and creatinine serum levels decreased in the experimental group and increased in the control group. Once more, however, this difference was not statistically significant. Conclusion — The administration of snakehead fish extract had no significant effect on albumin, urea, or creatinine serum levels in patients undergoing radiotherapy.