{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,2]],"date-time":"2026-04-02T16:09:30Z","timestamp":1775146170725,"version":"3.50.1"},"reference-count":80,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2021,10,14]],"date-time":"2021-10-14T00:00:00Z","timestamp":1634169600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Deputyship for Research &amp; Innovation, Ministry of Education in Saudi Arabia","award":["IF-2020-013-Eng"],"award-info":[{"award-number":["IF-2020-013-Eng"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The prevalence of diabetes is increasing globally. More than 690 million cases of diabetes are expected worldwide by 2045. Continuous blood glucose monitoring is essential to control the disease and avoid long-term complications. Diabetics suffer on a daily basis with the traditional glucose monitors currently in use, which are invasive, painful, and cost-intensive. Therefore, the demand for non-invasive, painless, economical, and reliable approaches to monitor glucose levels is increasing. Since the last decades, many glucose sensing technologies have been developed. Researchers and scientists have been working on the enhancement of these technologies to achieve better results. This paper provides an updated review of some of the pioneering non-invasive optical techniques for monitoring blood glucose levels that have been proposed in the last six years, including a summary of state-of-the-art error analysis and validation techniques.<\/jats:p>","DOI":"10.3390\/s21206820","type":"journal-article","created":{"date-parts":[[2021,10,14]],"date-time":"2021-10-14T23:02:16Z","timestamp":1634252536000},"page":"6820","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":98,"title":["A Review of Non-Invasive Optical Systems for Continuous Blood Glucose Monitoring"],"prefix":"10.3390","volume":"21","author":[{"given":"Bushra","family":"Alsunaidi","sequence":"first","affiliation":[{"name":"Biomedical Engineering Department, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8084-6916","authenticated-orcid":false,"given":"Murad","family":"Althobaiti","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Department, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3553-3531","authenticated-orcid":false,"given":"Mahbubunnabi","family":"Tamal","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Department, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia"}]},{"given":"Waleed","family":"Albaker","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam 31451, Saudi Arabia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7499-0655","authenticated-orcid":false,"given":"Ibraheem","family":"Al-Naib","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Department, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia"}]}],"member":"1968","published-online":{"date-parts":[[2021,10,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"384","DOI":"10.1055\/s-0034-1366278","article-title":"Definition, classification and diagnosis of diabetes mellitus","volume":"122","author":"Kerner","year":"2014","journal-title":"Exp. Clin. Endocrinol. Diabetes"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"S13","DOI":"10.2337\/dc18-S002","article-title":"2. Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes\u20142018","volume":"41","author":"Association","year":"2018","journal-title":"Diabetes Care"},{"key":"ref_3","unstructured":"Davis, B. (2021, October 06). What Is the Pathophysiology of Diabetes Mellitus?. Available online: https:\/\/www.mvorganizing.org\/what-is-the-pathophysiology-of-diabetes-mellitus\/."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1165","DOI":"10.1210\/jcem.84.4.5612","article-title":"Type 2 Diabetes Mellitus: Update on Diagnosis, Pathophysiology, and Treatment","volume":"84","author":"Mahler","year":"1999","journal-title":"J. Clin. Endocrinol. Metab."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Gonzales, W.V., Mobashsher, A.T., and Abbosh, A. (2019). The progress of glucose monitoring\u2014A review of invasive to minimally and non-invasive techniques, devices and sensors. Sensors, 19.","DOI":"10.3390\/s19040800"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"131","DOI":"10.4103\/2228-7477.161463","article-title":"Regulation of blood glucose concentration in type 1 diabetics using single order sliding mode control combined with fuzzy on-line tunable gain, a simulation study","volume":"5","author":"Dinani","year":"2015","journal-title":"J. Med. Signals Sens."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1039","DOI":"10.1210\/en.2011-1499","article-title":"Minireview: Glucagon in the Pathogenesis of Hypoglycemia and Hyperglycemia in Diabetes","volume":"153","author":"Cryer","year":"2012","journal-title":"Endocrinology"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"107843","DOI":"10.1016\/j.diabres.2019.107843","article-title":"Global and regional diabetes prevalence estimates for 2019 and projections for 2030 and 2045: Results from the International Diabetes Federation Diabetes Atlas, 9th edition","volume":"157","author":"Saeedi","year":"2019","journal-title":"Diabetes Res. Clin. Pract."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"American Diabetes Association (2018). Economic Costs of Diabetes in the U.S. in 2017. Diabetes Care, 41, 917\u2013928.","DOI":"10.2337\/dci18-0007"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Bruen, D., Delaney, C., Florea, L., and Diamond, D. (2017). Glucose sensing for diabetes monitoring: Recent developments. Sensors, 17.","DOI":"10.3390\/s17081866"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"579","DOI":"10.1007\/s12325-019-0870-x","article-title":"Continuous Glucose Monitoring: A Brief Review for Primary Care Practitioners","volume":"36","author":"Ajjan","year":"2019","journal-title":"Adv. Ther."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"603","DOI":"10.1109\/JBHI.2019.2908488","article-title":"Convolutional Recurrent Neural Networks for Glucose Prediction","volume":"24","author":"Li","year":"2020","journal-title":"IEEE J. Biomed. Health Inform."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"543","DOI":"10.1080\/05704928.2018.1486324","article-title":"A review of optical methods for continuous glucose monitoring","volume":"54","author":"Jernelv","year":"2019","journal-title":"Appl. Spectrosc. Rev."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1059","DOI":"10.1038\/s41598-018-19340-y","article-title":"In vivo Microscopic Photoacoustic Spectroscopy for Non-Invasive Glucose Monitoring Invulnerable to Skin Secretion Products","volume":"8","author":"Sim","year":"2018","journal-title":"Sci. Rep."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Shokrekhodaei, M., and Quinones, S. (2020). Review of non-invasive glucose sensing techniques: Optical, electrical and breath acetone. Sensors, 20.","DOI":"10.3390\/s20051251"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Zhang, R., Liu, S., Jin, H., Luo, Y., Zheng, Z., Gao, F., and Zheng, Y. (2019). Noninvasive Electromagnetic Wave Sensing of Glucose. Sensors, 19.","DOI":"10.3390\/s19051151"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1007\/s00216-018-1395-x","article-title":"Non-invasive monitoring of blood glucose using optical methods for skin spectroscopy\u2014Opportunities and recent advances","volume":"411","author":"Delbeck","year":"2019","journal-title":"Anal. Bioanal. Chem."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"047003","DOI":"10.1117\/1.JBO.20.4.047003","article-title":"Near-infrared noninvasive blood glucose prediction without using multivariate analyses: Introduction of imaginary spectra due to scattering change in the skin","volume":"20","author":"Maruo","year":"2015","journal-title":"J. Biomed. Opt."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"014022","DOI":"10.1117\/1.2165572","article-title":"Comparison between transmittance and reflectance measurements in glucose determination using near infrared spectroscopy","volume":"11","author":"Jeon","year":"2006","journal-title":"J. Biomed. Opt."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Li, X., and Li, C. (2016, January 23\u201327). Research on non-invasive glucose concentration measurement by NIR transmission. Proceedings of the 2015 IEEE International Conference on Computer and Communications, St. Louis, MO, USA.","DOI":"10.1109\/CompComm.2015.7387571"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Siesler, H., Ozaki, Y., Kawata, S., and Heise, H.M. (2002). Near-Infrared Spectroscopy, Principles, Instruments, Applications, Wiley.","DOI":"10.1002\/9783527612666"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"214","DOI":"10.1016\/j.bspc.2015.01.005","article-title":"Prospects and limitations of non-invasive blood glucose monitoring using near-infrared spectroscopy","volume":"18","author":"Yadav","year":"2015","journal-title":"Biomed. Signal Process. Control"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1016\/j.snb.2019.01.121","article-title":"Wearable-band type visible-near infrared optical biosensor for non-invasive blood glucose monitoring","volume":"286","author":"Rachim","year":"2019","journal-title":"Sens. Actuators B Chem."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1109\/JPHOT.2016.2616491","article-title":"Optical Based Noninvasive Glucose Monitoring Sensor Prototype","volume":"8","author":"Haxha","year":"2016","journal-title":"IEEE Photonics J."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1109\/JPHOT.2021.3079408","article-title":"Optimization of Dual-Channel Near-Infrared Non-Invasive Glucose Level Measurement Sensors Based on Monte-Carlo Simulations","volume":"13","author":"Althobaiti","year":"2021","journal-title":"IEEE Photonics J."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1109\/TCE.2020.3011966","article-title":"IGLU 2.0: A New Wearable for Accurate Non-Invasive Continuous Serum Glucose Measurement in IoMT Framework","volume":"66","author":"Joshi","year":"2020","journal-title":"IEEE Trans. Consum. Electron."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"289","DOI":"10.1364\/BOE.9.000289","article-title":"Noninvasive glucose monitoring using mid-infrared absorption spectroscopy based on a few wavenumbers","volume":"9","author":"Kasahara","year":"2018","journal-title":"Biomed. Opt. Express"},{"key":"ref_28","first-page":"59","article-title":"The Evolution of Non-invasive Blood Glucose Monitoring System for Personal Application","volume":"8","author":"Saad","year":"2016","journal-title":"J. Telecommun. Electron. Comput. Eng."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Kumar, D.A., and Jayanthy, T. (2020, January 28\u201330). Review on Non-Invasive Blood Glucose Measurement Techniques. Proceedings of the 2020 IEEE International Conference on Communication and Signal Processing, ICCSP 2020, Chennai, India.","DOI":"10.1109\/ICCSP48568.2020.9182268"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"eaay5206","DOI":"10.1126\/sciadv.aay5206","article-title":"Direct observation of glucose fingerprint using in vivo Raman spectroscopy","volume":"6","author":"Kang","year":"2020","journal-title":"Sci. Adv."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1038\/nphoton.2007.3","article-title":"Cutting-edge terahertz technology","volume":"1","author":"Tonouchi","year":"2007","journal-title":"Nat. Photonics"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"910","DOI":"10.1109\/22.989974","article-title":"Terahertz technology","volume":"50","author":"Siegel","year":"2002","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"2438","DOI":"10.1109\/TMTT.2004.835916","article-title":"Terahertz technology in biology and medicine","volume":"52","author":"Siegel","year":"2004","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"124","DOI":"10.1002\/lpor.201000011","article-title":"Terahertz spectroscopy and imaging -Modern techniques and applications","volume":"5","author":"Jepsen","year":"2011","journal-title":"Laser Photon. Rev."},{"key":"ref_35","first-page":"4700405","article-title":"Biomedical Sensing with Conductively Coupled Terahertz Metamaterial Resonators","volume":"23","year":"2017","journal-title":"IEEE J. Sel. Top. Quantum Electron."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"D\u2019Arco, A., Di Fabrizio, M., Dolci, V., Petrarca, M., and Lupi, S. (2020). THz Pulsed Imaging in Biomedical Applications. Condens. Matter, 5.","DOI":"10.3390\/condmat5020025"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"345","DOI":"10.21037\/qims.2017.06.02","article-title":"Recent advances in terahertz technology for biomedical applications","volume":"7","author":"Sun","year":"2017","journal-title":"Quant. Imaging Med. Surg."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"2397","DOI":"10.1364\/BOE.5.002397","article-title":"Noninvasive in vivo glucose sensing on human subjects using mid-infrared light","volume":"5","author":"Liakat","year":"2014","journal-title":"Biomed. Opt. Express"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1051\/epjconf\/201714905013","article-title":"Terahertz spectroscopy for diabetes diagnostics","volume":"149","author":"Cherkasova","year":"2017","journal-title":"EPJ Web Conf."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s11082-016-0490-5","article-title":"Noninvasive blood glucose monitoring in the terahertz frequency range","volume":"48","author":"Cherkasova","year":"2016","journal-title":"Opt. Quantum Electron."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"020008","DOI":"10.1063\/1.5098152","article-title":"Glucose level sensor based on metasurface in THz frequency range","volume":"2098","author":"Gusev","year":"2019","journal-title":"AIP Conf. Proc."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"399","DOI":"10.1007\/s10762-017-0462-2","article-title":"Quantify Glucose Level in Freshly Diabetic\u2019s Blood by Terahertz Time-Domain Spectroscopy","volume":"39","author":"Chen","year":"2018","journal-title":"J. Infrared Millim. Terahertz Waves"},{"key":"ref_43","first-page":"1","article-title":"Highly sensitive and selective sugar detection by terahertz nano-antennas","volume":"5","author":"Lee","year":"2015","journal-title":"Sci. Rep."},{"key":"ref_44","first-page":"1","article-title":"Terahertz imaging for early screening of diabetic foot syndrome: A proof of concept","volume":"7","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"122213","DOI":"10.1016\/j.talanta.2021.122213","article-title":"A novel THz molecule-selective sensing strategy in aqueous environments: THz-ATR spectroscopy integrated with a smart hydrogel","volume":"228","author":"Zhou","year":"2021","journal-title":"Talanta"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"12127","DOI":"10.3390\/s140712127","article-title":"In vitro evaluation of fluorescence glucose biosensor response","volume":"14","author":"Aloraefy","year":"2014","journal-title":"Sensors"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"335","DOI":"10.19101\/IJATEE.2018.546008","article-title":"Blood glucose monitoring techniques: Recent advances, challenges and future perspectives","volume":"5","author":"Gamessa","year":"2018","journal-title":"Int. J. Adv. Technol. Eng. Explor."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"1","DOI":"10.14302\/issn.2374-9431.jbd-15-647","article-title":"Review: Non-Invasive Continuous Blood Glucose Measurement Techniques","volume":"1","author":"Nawaz","year":"2016","journal-title":"J. Bioinforma. Diabetes"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"663","DOI":"10.1109\/TCSI.2017.2724012","article-title":"Cloud Computing-Based Non-Invasive Glucose Monitoring for Diabetic Care","volume":"65","author":"Pai","year":"2018","journal-title":"IEEE Trans. Circuits Syst. Regul. Pap."},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Izatt, J.A., Choma, M.A., and Dhalla, A.H. (2015). Theory of optical coherence tomography. Optical Coherence Tomography: Technology and Applications, Springer.","DOI":"10.1007\/978-3-319-06419-2_3"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"D30","DOI":"10.1364\/AO.49.000D30","article-title":"High-speed optical coherence tomography: Basics and applications","volume":"49","author":"Wojtkowski","year":"2010","journal-title":"Appl. Opt."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"525","DOI":"10.1002\/jbio.201200243","article-title":"Optical coherence tomography for advanced screening in the primary care office","volume":"7","author":"Shelton","year":"2014","journal-title":"J. Biophotonics"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"98","DOI":"10.1016\/j.oooo.2016.03.021","article-title":"Tissue characterization using optical coherence tomography and cone beam computed tomography: A comparative pilot study","volume":"122","author":"Mahdian","year":"2016","journal-title":"Oral Surg. Oral Med. Oral Pathol. Oral Radiol."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"5182","DOI":"10.1364\/BOE.7.005182","article-title":"Classification and analysis of human ovarian tissue using full field optical coherence tomography","volume":"7","author":"Nandy","year":"2016","journal-title":"Biomed. Opt. Express"},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"3806","DOI":"10.1364\/BOE.6.003806","article-title":"Correlating optical coherence elastography based strain measurements with collagen content of the human ovarian tissue","volume":"6","author":"Nandy","year":"2015","journal-title":"Biomed. Opt. Express"},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"992","DOI":"10.1364\/OL.26.000992","article-title":"Noninvasive monitoring of glucose concentration with optical coherence tomography","volume":"26","author":"Esenaliev","year":"2001","journal-title":"Opt. Lett."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"2263","DOI":"10.2337\/diacare.25.12.2263","article-title":"Noninvasive blood glucose monitoring with optical coherence tomography: A pilot study in human subjects","volume":"25","author":"Larin","year":"2002","journal-title":"Diabetes Care"},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"1371","DOI":"10.1088\/0031-9155\/48\/10\/310","article-title":"Specificity of noninvasive blood glucose sensing using optical coherence tomography technique: A pilot study","volume":"48","author":"Larin","year":"2003","journal-title":"Phys. Med. Biol."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"086007","DOI":"10.1117\/1.JBO.21.8.086007","article-title":"Optical coherence tomography for blood glucose monitoring in vitro through spatial and temporal approaches","volume":"21","author":"Yoshimura","year":"2016","journal-title":"J. Biomed. Opt."},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"087033","DOI":"10.1117\/1.JBO.22.8.087003","article-title":"Accurate viscosity measurements of flowing aqueous glucose solutions with suspended scatterers using a dynamic light scattering approach with optical coherence tomography","volume":"22","author":"Weatherbee","year":"2017","journal-title":"J. Biomed. Opt."},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"15179","DOI":"10.1364\/OE.25.015179","article-title":"Differential Mueller matrix polarimetry technique for non-invasive measurement of glucose concentration on human fingertip","volume":"25","author":"Phan","year":"2017","journal-title":"Opt. Express"},{"key":"ref_62","doi-asserted-by":"crossref","first-page":"047001","DOI":"10.1117\/1.JBO.23.4.047001","article-title":"Noninvasive measurement of glucose concentration on human fingertip by optical coherence tomography","volume":"23","author":"Chen","year":"2018","journal-title":"J. Biomed. Opt."},{"key":"ref_63","doi-asserted-by":"crossref","unstructured":"Lundsgaard-Nielsen, S.M., Pors, A., Banke, S.O., Henriksen, J.E., Hepp, D.K., and Weber, A. (2018). Critical-depth Raman spectroscopy enables home-use non-invasive glucose monitoring. PLoS ONE, 13.","DOI":"10.1371\/journal.pone.0197134"},{"key":"ref_64","unstructured":"(2021, July 13). ISO\u2014ISO 15197:2013\u2014In Vitro Diagnostic Test Systems\u2014Requirements for Blood-Glucose Monitoring Systems for Self-Testing in Managing Diabetes Mellitus. Available online: https:\/\/www.iso.org\/standard\/54976.html."},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"658","DOI":"10.1177\/1932296814539589","article-title":"The surveillance error grid","volume":"8","author":"Klonoff","year":"2014","journal-title":"J. Diabetes Sci. Technol."},{"key":"ref_66","doi-asserted-by":"crossref","first-page":"S49","DOI":"10.1002\/dmrr.210","article-title":"Glucose monitoring by reverse iontophoresis","volume":"18","author":"Potts","year":"2002","journal-title":"Diabetes. Metab. Res. Rev."},{"key":"ref_67","doi-asserted-by":"crossref","unstructured":"Anand, P.K., Shin, D.R., and Memon, M.L. (2020). Adaptive Boosting Based Personalized Glucose Monitoring System (PGMS) for Non-Invasive Blood Glucose Prediction with Improved Accuracy. Diagnostics, 10.","DOI":"10.3390\/diagnostics10050285"},{"key":"ref_68","unstructured":"(2021, July 13). Self-Monitoring Blood Glucose Test Systems for Over-the-Counter Use|FDA, Available online: https:\/\/www.fda.gov\/regulatory-information\/search-fda-guidance-documents\/self-monitoring-blood-glucose-test-systems-over-counter-use."},{"key":"ref_69","doi-asserted-by":"crossref","first-page":"477","DOI":"10.1210\/edrv.19.4.0336","article-title":"Insulin resistance versus insulin deficiency in non-insulin-dependent diabetes mellitus: Problems and prospects","volume":"19","author":"Ferrannini","year":"1998","journal-title":"Endocr. Rev."},{"key":"ref_70","doi-asserted-by":"crossref","unstructured":"Bakker, G.J., Vanbellinghen, M.C., Scheithauer, T.P., Verchere, C.B., Stroes, E.S., Timmers, N.K.L.M., Herrema, H., Nieuwdorp, M., Verberne, H.J., and van Raalte, D.H. (2019). Pancreatic 18F-FDG uptake is increased in type 2 diabetes patients compared to non-diabetic controls. PLoS ONE, 14.","DOI":"10.1371\/journal.pone.0213202"},{"key":"ref_71","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/2191-219X-3-50","article-title":"The relation between the blood glucose level and the FDG uptake of tissues at normal PET examinations","volume":"3","author":"Lindholm","year":"2013","journal-title":"EJNMMI Res."},{"key":"ref_72","doi-asserted-by":"crossref","first-page":"1178","DOI":"10.1177\/1932296818758769","article-title":"Evaluation of a New Noninvasive Glucose Monitoring Device by Means of Standardized Meal Experiments","volume":"12","author":"Strobl","year":"2018","journal-title":"J. Diabetes Sci. Technol."},{"key":"ref_73","doi-asserted-by":"crossref","first-page":"1159","DOI":"10.1177\/1932296818763457","article-title":"(Joseph) Device and Method for Noninvasive Glucose Assessment","volume":"12","author":"Segman","year":"2018","journal-title":"J. Diabetes Sci. Technol."},{"key":"ref_74","unstructured":"Cnoga (2021, July 13). CoG\u2014Hybrid Glucometer|Cnoga Digital Care. Available online: https:\/\/www.cnogacare.co\/cog-hybrid-glucometer."},{"key":"ref_75","doi-asserted-by":"crossref","first-page":"3393","DOI":"10.1080\/14767058.2018.1463987","article-title":"Noninvasive, continuous, real-time glucose measurements compared to reference laboratory venous plasma glucose values","volume":"32","author":"Hadar","year":"2018","journal-title":"J. Matern. Fetal. Neonatal Med."},{"key":"ref_76","unstructured":"Reddy, N., Verma, N., and Dungan, K. (2020). Monitoring Technologies-Continuous Glucose Monitoring, Mobile Technology, Biomarkers of Glycemic Control. Endotext, Available online: https:\/\/www.ncbi.nlm.nih.gov\/sites\/books\/NBK279046\/."},{"key":"ref_77","doi-asserted-by":"crossref","first-page":"9628281","DOI":"10.1155\/2020\/9628281","article-title":"Noninvasive Glucose Measurement Using Machine Learning and Neural Network Methods and Correlation with Heart Rate Variability","volume":"2020","author":"Gusev","year":"2020","journal-title":"J. Sens."},{"key":"ref_78","first-page":"1","article-title":"Non-Invasive Glucose Monitoring: A Review of Challenges and Recent Advances","volume":"6","author":"Lin","year":"2017","journal-title":"Curr. Trends Biomed. Eng. Biosci."},{"key":"ref_79","unstructured":"(2021, July 13). Eversense Continuous Glucose Monitoring|Long-Term Continuous Glucose Monitor. Available online: https:\/\/www.eversensediabetes.com\/."},{"key":"ref_80","unstructured":"(2021, July 13). Eversense Continuous Glucose Monitoring System\u2014P160048\/S006|FDA, Available online: https:\/\/www.fda.gov\/medical-devices\/recently-approved-devices\/eversense-continuous-glucose-monitoring-system-p160048s006."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/20\/6820\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:12:58Z","timestamp":1760166778000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/20\/6820"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,10,14]]},"references-count":80,"journal-issue":{"issue":"20","published-online":{"date-parts":[[2021,10]]}},"alternative-id":["s21206820"],"URL":"https:\/\/doi.org\/10.3390\/s21206820","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,10,14]]}}}