What is a typical signature (sig) for a Continuous Glucose Monitor (CGM)?

Appropriate Signature (Sig) for Continuous Glucose Monitor (CGM) Prescription

The appropriate signature (sig) for a Continuous Glucose Monitor (CGM) should include "Apply one sensor to the back of the upper arm or abdomen every 10-14 days as directed" with specific wear duration based on the device model.

Standard CGM Prescription Components

When prescribing a CGM, the signature should include the following essential elements:

1. Application site: Back of upper arm or abdomen (depending on device specifications)
2. Frequency of application: Every 10-14 days (device-specific)
3. Duration of use: Typically 14 days for most current systems
4. Monitoring parameters: For continuous glucose monitoring

Example Prescription Format

Continuous Glucose Monitor [specific brand/model]
Sig: Apply one sensor to [specific site] every [X] days for continuous glucose monitoring
Dispense: [quantity] sensors
Refills: [number]

Device-Specific Considerations

Different CGM systems have varying wear durations that should be specified in the sig 1:

• 14-day systems (most current CGMs): "Apply one sensor to the back of upper arm every 14 days"
• 10-day systems: "Apply one sensor to the back of upper arm every 10 days"
• 7-day systems (older models): "Apply one sensor to the abdomen every 7 days"

Clinical Metrics to Include

The prescription should also specify the standardized CGM metrics for clinical monitoring 1:

• Time in range (TIR): 70-180 mg/dL (3.9-10.0 mmol/L)
• Target percentage of readings in range: >70% for most patients
• Minimum wear time: 70% of time over 14 days for accurate assessment

Additional Prescription Elements

For comprehensive care, consider including these elements in the prescription or accompanying documentation:

• Calibration requirements: "Factory calibrated" or "Calibrate with fingerstick glucose X times daily" (device-dependent)
• Data download frequency: "Download data every 14 days for review"
• Target metrics: "Goal: >70% time in range (70-180 mg/dL)"

Common Pitfalls to Avoid

1. Failing to specify the exact wear duration - Each CGM model has specific wear periods that must be followed
2. Not indicating proper application site - Different devices require specific anatomical locations
3. Omitting quantity and refill information - Insurance coverage often depends on proper documentation
4. Neglecting to specify if the CGM is for therapeutic (non-adjunctive) use - Important for insurance coverage 1

Insurance Documentation Considerations

For optimal insurance coverage, include language that addresses:

• Medical necessity based on diabetes type
• Previous therapy (insulin regimen, history of hypoglycemia)
• Expected clinical benefits (improved glycemic control, reduced hypoglycemia risk)

Remember that CGM data should be downloaded and reviewed regularly, with standardized metrics as outlined in the 2019 international consensus guidelines 1, to effectively monitor and adjust diabetes management.