In this report, we examined a noninvasive blood glucose monitoring system based on Fourier transform infrared spectroscopy (FT-IR) in the mid-infrared (MIR) region. MIR spectroscopy detects the fundamental vibrations of molecules and this gives more distinct glucose peaks than NIR spectroscopy. To overcome the problem of limited light penetration due to large absorption coefficients, the attenuated total reflection (ATR) method is usually applied for MIR spectroscopy. In this method, a prism made of high-refractive-index materials, such as diamond and silicon, is used and the absorption of samples that are in contact with the prism surface is detected when the evanescent field produced by total reflection is absorbed. The intensities of the absorption peaks detected by the MIR-ATR method are much higher than those detected by the NIR spectroscopy, and most of the peaks are isolated. Thus, accurate and reliable measurements can be performed without complicated calculations to remove interference between the peaks. There have been many reports of applying MIR-ATR methods for blood glucose measurement including ones measuring glucose levels of whole blood,8–10 urine,11 and serum.12,13 Some groups reported that they have attempted to measure blood glucose levels in vivo by using an ATR prism with MIR lasers14,15 and an FT-IR spectrometer.16 These methods mainly detect glucose in interstitial fluid that reflects the blood glucose level17 because the penetration depth of MIR-ATR spectroscopy is limited to a few microns. Also, the area to be measured is limited to the finger tips because of the bulky measurement equipment.