Phenylketonuria (PKU) is a rare inborn error of metabolism and affects both kids and adults. PKU occurs due to the buildup of phenylalanine in the human body. If PKU is not detected and treated in its early stages, it causes disability both physically and mentally. Many countries have been performing newborn screening tests for PKU metabolic disorder. Treatment for PKU is completely diet-based, and the person with PKU should be constantly monitored for phenylalanine (Phe) levels of the blood to avoid its effects. The present methods of detecting PKU are time-consuming and complex. Laboratory-based testing does not allow for the rapid return of the test result for monitoring the patients with PKU. This typical test turn-around time of several days for the current testing method prolonged for effective monitoring and treatment of the person suffering from PKU. This project is to develop a new at-home urine-based testing method that helps monitor levels of Phe of a person with PKU. This project makes testing easy by using iron (III) chloride and porous PCL-based biosensors to detect PKU. This test of detecting PKU improves the sensitivity to the presence of L-phenylalanine in the urine. The biosensors were developed and tested with PKU solution based on color changes in the biosensors. The tests were performed on the biosensors with various concentrations of PKU solutions. By quantitative measurement of color using Red Green Blue (RGB), Hue Saturation Lightness (HSL), and Cyan Magenta Yellow, and Key (CMYK), PKU could be detected. The additional accuracy of this test method is provided by implementing a light-controlling custom-made device. The results show that a combination of 10% iron (III) chloride tested with higher concentrations of PKU solutions gives the best results to confirm the presence of L-Phenylalanine. The final test results show that the proposed method is simple, safe, and low-cost for an ordinary person to do at home. Further optimization and calibration will be required for the test to be commercially viable.