THE IDEA

1962: the enzyme electrode

In 1962 Leland Clark proposed combining an enzyme with an electrode so that a reaction with glucose would produce an electrical signal. That idea, an enzyme electrode, is still the core of most glucose sensors today.

The big idea is more than 60 years old. Everything since has been making it small, stable, and wearable.

AT HOME

Strips and meters

Through the 1970s and 1980s, handheld meters and disposable test strips let people measure their own blood glucose at home. A strip holds the enzyme and electrodes, and the meter reads the current from one drop of blood.

A test strip is a single-use version of the same enzyme electrode.

CONTINUOUS

The first CGMs

1999 The first FDA-approved CGM recorded data that was reviewed afterward, not live

2000s Real-time CGMs arrived from Medtronic and Dexcom, with short wear times and frequent fingerstick calibration

2014 to 2017 Abbott's FreeStyle Libre launched in Europe and then the U.S.

Early CGMs were short-lived and needed regular fingerstick calibration.

BETTER AND EASIER

Calibration-free and long-lasting

2018 Dexcom G6 was cleared without routine fingerstick calibration, which is called factory calibration

2018 Eversense became the first fully implantable CGM in the U.S.

2022 Dexcom G7 combined sensor and transmitter into one small disposable

Each step made sensors smaller, easier to wear, and less work.

NOW

Sensors without a prescription

In 2024 the FDA cleared the first over-the-counter CGMs, Dexcom's Stelo and Abbott's Lingo, for adults who do not use insulin. They aim at wellness and understanding food and exercise, not at insulin dosing.

CGMs are moving from a medical device for a few to a health tool for many.

UNIT 3 STUDY COMPLETE

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You've covered how glucose sensing went from strips and meters to wearable sensors.