Dexcom G4 and G5 systems: costs and differences
Dexcom has kept two generations of CGM systems alive in parallel. These two generations have different abilities: the newer generation is not automatically better for all users.
The G4 and the G5 systems use the same sensor. A single Dexcom G4/G5 Platinum sensor can be purchased either directly from Dexcom or through various distributors in the price range of $70 ~ $80. The Dexcom G4/G5 sensors are typically sold and distributed with four sensors per box.
The Dexcom G4/G5 sensor is FDA approved for 7 days of continuous use. Many patients can make a sensor last 2 weeks, some can go up to 3-4 weeks.
Transmitter: cost and duration
The G4 and the G5 systems use different transmitters. The transmitters’ footprints are the same, since they must fit in the same sensor bed, but the G4 transmitter is a bit thinner than the G5.
The G4 transmitter costs $600, and has a long-lasting battery, that is guaranteed for 6 months, but can often last a lot longer, up to a year. More importantly, although the manufacturer does not recognize this capability, it is possible to change the G4 battery doing heavy DIY, or have it done by a third party, and reuse the G4 transmitter. This represents very significant savings for self-funded patients.
The G5 transmitter costs $300, half the price of the G4 transmitter, but its duration is limited by software to between 105 and 112 days – even if the battery is changed (a non-trivial DIY procedure) an old G5 transmitter won’t be accepted by a Dexcom G5 system. So, while the nominal cost appears the same, the G4 transmitter system cost can be made a lot lower than the G5’s.
Transmitter: Bluetooth capability
The G4 transmitter cannot broadcast over Bluetooth, while the G5 transmitter can. This means the G5 transmitter can send data directly to cellphones, while the G4 transmitter cannot.
Over the course of a day, for one reason or another there is often no receiver within range of a transmitter for some period of time. With a G4 system, the data is lost. However, the G5 transmitter, when communicating with an iOS or Android app (but not with a regular receiver), can backfill up to 3 hours of information – a feature that I find significant in practice. For instance, it makes sports events for kids a lot more manageable.
The receiving devices are significantly different between the G4 and the G5 systems. The G4 system has two receivers: the regular G4 receiver, and the G4 receiver with Share (not available in all countries). The G4 receiver with Share can rebroadcast the CGM data over Bluetooth to a cellphone. In turn, the cellphone can relay the data to Dexcom data servers.
The G5 receiver does not have share capability, but the G5 transmitter can be received directly by any iOS phone and by some Android phones, any of which can relay data to the Dexcom servers. So, with a G5 system, you don’t need to use a G5 receiver – instead, you can use your phone as a receiver.
Regular G4 and G5 receivers have an official price of $600, but for patients paying out of pocket Dexcom makes it possible to obtain them for $300.
Receiving CGM info on a watch
If you have an iOS phone, your phone can relay CGM information through Bluetooth to an Apple Watch, in which case you can check your CGM info directly on your Apple Watch.
If you have an Android phone, a combination of opensource applications (NighScout and xDrip) also allow you to receive data on specific Android watch models.
The value of relaying data to Dexcom data servers
There are two valuable benefits to being able to relay real-time CGM data to the Dexcom data servers:
Dexcom can provide powerful analytics to the user, who can review the data of days and weeks, and make adjustments based on trends. For that purpose, the data is made available with a 3-hour delay. When using a receiver that cannot use Bluetooth, it is possible to upload the data to the Dexcom servers by connecting the receiver to a computer through a USB port.
Dexcom can make that data immediately available to other phones through a Dexcom Follow app. This way, other family members, such as parents or spouses, can have access to the PWD’s real-time CGM data. This is invaluable to parents of CWDs for instance.