Impedance spectroscopy helps test for blood sugar noninvasively

Recognizing that current methods for diabetes patients to measure their blood sugar are painful and inconvenient, an international team of researchers from RWTH Aachen University in Germany, Delft University of Technology (The Netherlands), and the Indian Institute of Technology (Delhi, India) have—using a spectroscopic technique—developed what they call an entirely noninvasive blood sugar test.

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To measure blood glucose concentrations, diabetes patients typically have to prick a finger to obtain a blood sample and then use a glucose monitor to determine whether or not to take insulin or eat something sugary. So, the research team turned to impedance spectroscopy to help develop a system for patients to determine blood glucose concentrations without having to obtain a blood sample.

The spectral lines obtained by impedance spectroscopy depend crucially on the concentration of glucose in a blood sample. First, the researchers used a standard solution in vitro that contained different concentrations of glucose. Then, they placed electrodes on the forearm of a volunteer and recorded the impedance spectrum through the skin without needing to pierce it. The reference then revealed the blood glucose concentration noninvasively.

However, with their prototype, there are several other factors that can affect such impedance spectra, including patient-to-patient variation in skin type and skin moisture as well as related factors that would affect readings day to day for the same patient. The team is investigating these issues, and intends to take their prototype to the next stage in research and development.

Full details of the work appear in the International Journal of Biomedical Engineering and Technology; for more information, please visit


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