THE DEVICE

A small disc on the arm

Where Worn on the back of the upper arm

Filament A very short, thin filament, around 5 mm long

Wear 14 days per sensor

Calibration Factory calibrated, with no fingersticks needed for calibration

The sensor and transmitter are one compact disposable, which keeps cost and size low.

WIRED ENZYME

A mediator holds the enzyme's hand

Abbott describes a wired enzyme design. The enzyme is linked to an osmium-based mediator that carries electrons to the electrode. In the terms of Unit 7, it is second-generation: it uses a mediator instead of depending on oxygen, and it works at a low voltage, which helps limit interference.

A different answer to the same wiring problem Dexcom solves with peroxide.

SCAN TO STREAM

How readings reach you

Libre 1 The user scans the sensor with a reader or phone to get a reading

Libre 2 Adds Bluetooth streaming with optional alarms

Libre 3 Streams a new reading about every minute

Later versions moved from on-demand scanning to continuous streaming.

CAUTIONS

Every sensor has a weak spot

Labeling for earlier FreeStyle Libre versions warns that taking large amounts of vitamin C (ascorbic acid) can falsely raise readings. As with any sensor, the current labeling lists what can interfere.

Different chemistry means different interfering substances.

SIDE BY SIDE

Two philosophies

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Dexcom

Peroxide detection at platinum, a new reading every 5 minutes, and a strong focus on alerts and integration

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FreeStyle Libre

A wired enzyme at low voltage, a small integrated disc, and up to one reading per minute

Both are factory calibrated, and both use an enzyme electrode.

UNIT 12 STUDY COMPLETE

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Ready for the Fab Challenge?

You've covered how FreeStyle Libre is built and how its chemistry differs.