NFC technology enables short-range standard wireless communication within a few centimeters by utilizing electromagnetic fields, which allows two-way interaction between two NFC-enabled devices. Besides their applications in security systems, mobile payments, and data transfer, this wireless communication technology is very attractive for the development of miniaturized and flexible biomedical devices, such as skin-wearable and implantable devices. Since NFC tags are capable of harvesting energy from readers, they can operate in a battery-free environment. Within proximity, sensor data can be transferred to a portable device in real-time for display and analysis, and it ensures continuous operation. One of the most important challenges of implementing NFC technology in miniaturized biomedical devices, however, is its short reading distances. This happens because changes in the size of the reader and tag coil result in low inductive coupling, which negatively impacts the reading distances. In our study, therefore, we investigate the optimization of tag and reader antenna designs to enhance the maximum working distance while minimizing the sizes of the antennas, which is crucial for the development of miniaturized biomedical sensors and devices. We fabricated a total of 24 tag and reader antennas with inductances of 2, 4, and 6 μH and diameters of 10, 15, 20 and 30 mm, and measured their resonant frequencies and reading distances. Our experimental and theoretical studies reveal that variations in the diameter and differing inductance of the coil significantly impact the antenna coupling coefficient, directly influencing the operational range between the tag and reader. This finding will provide us with an in-depth understanding and a pathway to optimize coil diameter and inductance to achieve maximum working distance as well as will bring a potential solution for the impactful application in small-scale biomedical sensors.