Do I need only the sensor and transmitter for a continuous glucose monitor (CGM), or are additional components required?

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Last updated: August 8, 2026 • View editorial policy

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CGM Components Required

Yes, you need both the sensor and transmitter for most continuous glucose monitoring (CGM) systems, plus a compatible receiver device (smartphone or dedicated receiver) to view your glucose data. 1

Essential Components

Core Hardware Requirements

For Real-Time CGM (rtCGM) systems:

  • Sensor: Inserted under the skin to measure glucose in interstitial fluid
  • Transmitter: Attaches to the sensor and wirelessly sends data
  • Receiver/Display device: Either a dedicated receiver or compatible smartphone app to view glucose readings continuously 1

For Intermittently Scanned CGM (isCGM):

  • Sensor: Same subcutaneous placement
  • Reader device: Smartphone or dedicated reader to scan the sensor (no separate transmitter needed for most isCGM systems like FreeStyle Libre) 1

Important Distinctions by System Type

The transmitter requirement varies by CGM type:

  • Most rtCGM systems (Dexcom G6, G7): Require both sensor AND transmitter as separate components 1
  • isCGM systems (FreeStyle Libre): Sensor has integrated transmission capability; you scan with a reader device 1
  • Implantable systems (Eversense E3): Fully implantable sensor with removable external transmitter 1, 2

Additional Supplies You'll Need

Ongoing Consumables

  • Replacement sensors: Every 7-14 days depending on the system 1
  • Adhesive patches: To secure the sensor/transmitter to your skin
  • Skin preparation supplies: Alcohol wipes, skin barrier wipes if you have adhesive sensitivity 1

Calibration Supplies (System-Dependent)

  • Blood glucose meter and test strips: Some older systems require fingerstick calibrations, though most modern CGMs are factory-calibrated and don't require this 1, 3
  • Current FDA-approved systems (Dexcom G6/G7, FreeStyle Libre 2 Plus, Eversense E3) are generally nonadjunctive, meaning you don't need blood glucose meter confirmation for insulin dosing decisions except in specific clinical situations 1

Critical Considerations

Device Compatibility

  • Verify your smartphone is compatible with the CGM app before purchasing
  • Some systems require a dedicated receiver if your phone isn't compatible
  • For integration with insulin pumps or automated insulin delivery (AID) systems, ensure the CGM is FDA-approved for that use 1

Uninterrupted Supply Access

You must have continuous access to replacement sensors and transmitters to avoid gaps in CGM data, which reduces the clinical benefit. Guidelines emphasize that rtCGM should be used "as close to daily as possible for maximal benefit" and isCGM should be scanned at minimum every 8 hours 1

Skin Reaction Management

  • Have a plan for managing adhesive reactions (irritant or allergic contact dermatitis), which occur with all skin-attached devices 1
  • Consider barrier wipes or alternative adhesives if you develop skin irritation
  • The Panther Program (pantherprogram.org/skin-solutions) offers resources for managing adhesive reactions 4

Environmental Factors

Be aware that temperature, humidity, and altitude can affect glucose readings. Most monitors will show an error if temperature is outside acceptable range 1

References

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.