Pain free glucose monitoring?

In endocrinology practice, I see many diabetes patients. One of the challenges they face is the burden of glucose monitoring using invasive fingerprick glucometers.

The gold standard of glucose measurement is to draw blood and run it at accredited laboratories. Because many diabetes patients need more frequent monitoring of glucose levels, they use a glucometer to self-monitor glucose levels. Approved glucometers are quite accurate in that they are supposed to provide glucose readings within 12% of the ㄱreference level in 95% of the time and within 15% of the reference level in 98% of the time in the US. However, patients have to prick their fingers to get a drop of blood every time. And it is painful.

Self glucose monitoring is essential in many diabetes patients because diet modification, exercise, and adjustment of medications all depend on glucose readings and patterns. But again, it is painful to poke fingers to get a drop of blood.

There has been lots of research to develop minimally invasive or noninvasive methods of measuring blood glucose levels. In clinical practice, the biggest development yet is continuous glucose monitoring (CGM). CGM uses a sensor with a small plastic needle staying under the skin that measures glucose about every 5 minutes. It was developed to provide more readings between finger-stick glucometer measurements in brittle type 2 and type 1 diabetes. Early generation CGM devices required calibration using glucometer readings. But as the technologies have improved, newer CGM devices are now accurate without calibration and able to replace painful conventional glucometers.

Abbot Freestyle Libre CGM ) and Dexcom G6 CGM ( ) do not require calibration. (Medtronic CGM and Eversense CGM still require calibration using conventional glucometers). But patients have to inject a sensor under the skin and carry it all the time up to 10 days for Dexcom G6 and 14 days for Libre. You cannot use CGM intermittently only when you need measurement. Also, CGM measures glucose from the space outside the blood vessels called interstitial fluid. Glucose readings from the interstitial fluid are not necessarily the same as blood glucose readings, more so when blood glucose levels rapidly change. Insurance companies usually apply strict criteria to cover CGM because of the cost. So it is still rare to use new CGM devices for routine infrequent (up to twice a day) glucose monitoring.

Any new technologies on the horizon? The article by Gonzales et al. (Sensors 2019;19:4:800 PMID 30781431) extensively reviews different technologies (optical, thermal, electrical, nanotechnology, etc.) There were FDA approved devices such as GlucoWatch but they were not good enough to survive. Below are recent developments. From my search, these are not FDA approved yet.

Glucotrack ( You put on an earclip on you earlobe and glucose level is measured non-invasively using ultrasound, thermal and electromagentic technology.

Cnoga Combo glucometer ( It uses spectroscopy to measure glucose levels non-invasively. It has both conventional invasive and new non-invasive glucometers in one device (Combo!). But the non-invasive device requires calibration using conventional finger prick glucometers (8 measurements/day x 3 days!) and is not to be used for treatment decision.

Heloextense ( ): It uses spectroscopy technology from the fingertip and measures glucose levels non-invasively. The company says it is not developed for diabetes patients though. It also requires calibration using conventional finger prick glucometers.

SugarBEAT ( It comes as a patch which painlessly draws a small amount of glucose molecules out of the interstitial fluid which naturally sits just below the top layer of skin. Glucose level is subsequently measured and transmitted.

Then what happened to the Google project to measure glucose from the cornea? The project was put on hold as announced on their blog 11/2018 saying “Our clinical work on the glucose-sensing lens demonstrated that there was insufficient consistency in our measurements of the correlation between tear glucose and blood glucose concentrations to support the requirements of a medical device.”  (

In summary, we do not have better choices available yet than conventional glucometers. Keeping a good journal of glucose readings, diet, activity, medicaitions/insulins is still the best way to improve diabetes control.