This chapter reviews several representative microfluidic devices according to the type of the biomarker and their applications in point-of-care testing (POCT). It provides an account of some seminal works in microfluidic-based protein detection that have adopted highly promising strategies in overcoming some of the challenges. As a powerful technique, microfluidic systems play an essential role in the POCT device. The achievement in biotechnology, including single-cell analysis, novel isothermal nucleic acid amplification, and enzyme-linked immunosorbent assay (ELISA), has provided patients both sensitive and specific diagnostic methods. These types of POCT devices are capable of detecting cell behavior, nucleic acid, protein, and small molecules by utilizing microfluidic chip as a core subunit. Glucose, cholesterol, creatinine, triglycerides, urea, lactate, and ammonia are the most common metabolites that have been used for POC diagnostic purposes. Products of metabolism that produce energy, process wastes, and nutrients or decompose and renew the tissues in the body are called metabolites.