Aqueous solutions cannot be detected using transmissive terahertz metamaterials because water strongly absorbs terahertz waves. Transmissive terahertz metamaterials are easier to integrate terahertz emitters and receivers into single and compact devices than reflective terahertz metamaterials. The detection of aqueous solutions using transmissive terahertz metamaterials is a big challenge. This work fabricates a transmissive terahertz metamaterial using a folding metamaterial comprising split-ring resonators (SRRs) with nano-profiles with a high aspect ratio of 41.4. The folding metamaterial has a small transmittance of -49dB at its resonance frequency, large transmittance contrast of approximately 6×104 with respect to the transmittance of its substrate, large refractive index sensitivity of 647 GHz/RIU, and large quality factor of 37. This result arises from the nano-profiles of the SRRs. The nano-profiles increase the surface areas of the SRRs, increasing their surface currents and enhancing the electromagnetic resonance of the folding metamaterial. The folding metamaterial detects a 188-μm-thick rabbit-blood layer that is deposited on it, which cannot be detected by using a common metamaterial. This result reveals that folding metamaterials have potential in detecting the products of live microorganisms with geometrical sizes up to several hundreds of micrometers, such as hydrogen gas, hydrocarbons, and antibodies.