In our daily life, there are various sources of pollution that adversely affect our health. Heavy metal is one of the main contaminants surrounding everyone in an ecosystem. Since lead ions cannot be metabolized by liver, it will stay in the blood, and if medical intervention is not provided, it can cause adverse health effects to nervous system, due to gradually accumulating lead ion concentration. Nowadays, there are several technologies that can detect lead ion concentration, but most of them will take long time or are not easy to operate, because they require laboratory based bulky equipment. Examples of such methodologies are inductively coupled plasma- mass spectrometry (ICP-MS) and atomic absorption spectroscopy (AAS), which are the most commonly employed heavy metal ion detection techniques. However, this is not desirable for every-day use or ‘in field’ monitoring. Based on the idea of homecare diagnostics, we have developed a heavy metal ion sensor to detect lead ions in whole blood, with high sensitivity, selectivity, wide dynamic range and great ease of operation. High electron mobility transistor (HEMT) based sensor has been widely used in various applications, because it has high sensitivity, stability in harsh environments and fast response times. The fabrication of HEMT chip has 4 steps: ICP mesa etching, ohmic contact metal deposition, interconnect metal deposition and SU8 passivation. The 1mm² HEMT chip is packaged by embedding in epoxy substrate in the shape and form of micro SD card. Ion selective membrane (ISM) is selectively immobilized on the channel. Using high field operation, the changes in ISM capacitance due to lead ion capture, is amplified by the HEMT and we can obtain a drain current signal that is proportional to the lead ion concentration, in whole blood. We can thus obtain high sensitivity and low detection limit, which is comparable to the traditional technologies such as ICP-MS (detection limit of Pb²⁺: 10^-10 M)