Terahertz biosensing has gained enormous attention in medical diagnosis. In this study, we demonstrated that our developed terahertz chemical microscope (TCM) could be used for sensing of small molecules such as calcium ion, stress biomarker cortisol with extremely consumption of sample solutions and high sensitivity. Calcium ion sensitive membrane and DNA aptamer were utilized for calcium ions and cortisol sensing, respectively. The approach is unique and shows great promising for creating better future healthcare.