CGM data analysis from readings coded at capture

A continuous glucose monitor (CGM) on a 5-minute cycle sends 288 glucose values a day. Kymolog codes each one under LOINC 99504‑3, in mg/dL, as it arrives, so the flowsheet and a 14-day study series start from identical values.

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LOINC 99504-3 · mg/dL · every 5 minutes · FHIR R4

Fig. 1. A CGM sensor on the skin and a day of its glucose trace, with the latest value in red.

A CGM reading, before and after coding

At 08:05 the sensor reports 142, the unit mg/dL and its serial number, and nothing else. The Kymolog™ edge agent codes the reading as an Observation, the record that Fast Healthcare Interoperability Resources (FHIR) keeps for one measurement, under LOINC 99504-3: glucose in interstitial fluid.

The code specifies the fluid because a sensor reads glucose in the fluid under the skin. A blood code such as 2339-0 would file CGM values beside meter and lab results. Kymolog also keeps the trend arrow and any high or low alarm the sensor reports on the same Observation.

Example reading: glucose 142 mg/dL

A CGM reading becomes an ObservationOn the left, the CGM sensor's record of one reading: glucose 142, units mg/dL, time 08:05:00 and serial 7F3A0219, with no code and no patient. On the right, the FHIR R4 Observation Kymolog files from it. The value 142, in red, becomes valueQuantity.value; mg/dL becomes the UCUM code mg/dL with the system http://unitsofmeasure.org; the time becomes effectiveDateTime 2026-10-03T08:05:00-04:00; the serial becomes the device reference Device/cgm-7f3a. Kymolog adds the two fields the sensor never sends: the code, LOINC 99504-3, Glucose [Mass/volume] in Interstitial fluid, and the subject, Patient/p-041, from the device's assignment to the patient.CGM SENSOR READINGFHIR R4 OBSERVATIONno codecodeLOINC 99504-3Glucose [Mass/volume] in Interstitial fluidADDED BY KYMOLOGglucose142valueQuantity.value142unitsmg/dLvalueQuantity.codemg/dLsystem http://unitsofmeasure.orgtime08:05:00effectiveDateTime2026-10-03T08:05:00-04:00serial7F3A0219deviceDevice/cgm-7f3ano patientsubjectPatient/p-041from the device's assignmentADDED BY KYMOLOG
A CGM reading becomes an ObservationOn the left, the CGM sensor's record of one reading: glucose 142, units mg/dL, time 08:05:00 and serial 7F3A0219, with no code and no patient. On the right, the FHIR R4 Observation Kymolog files from it. The value 142, in red, becomes valueQuantity.value; mg/dL becomes the UCUM code mg/dL with the system http://unitsofmeasure.org; the time becomes effectiveDateTime 2026-10-03T08:05:00-04:00; the serial becomes the device reference Device/cgm-7f3a. Kymolog adds the two fields the sensor never sends: the code, LOINC 99504-3, Glucose [Mass/volume] in Interstitial fluid, and the subject, Patient/p-041, from the device's assignment to the patient.CGM SENSOR READINGno codeglucose142unitsmg/dLtime08:05:00serial7F3A0219no patientcoded at the edgeFHIR R4 OBSERVATIONcodeADDEDLOINC 99504-3Glucose [Mass/volume] in Interstitial fluidvalueQuantity.value142valueQuantity.codemg/dLsystem http://unitsofmeasure.orgeffectiveDateTime2026-10-03T08:05:00-04:00deviceDevice/cgm-7f3asubjectADDEDPatient/p-041from the device's assignment
Figure 2 as a table
FieldFiled asFrom the sensor
codeLOINC 99504-3, glucose in interstitial fluidnothing: Kymolog adds it
valueQuantity.value142glucose 142
valueQuantity.codemg/dL, a UCUM codeunits mg/dL
effectiveDateTime2026-10-03T08:05:00-04:00time 08:05:00
deviceDevice/cgm-7f3aserial 7F3A0219
subjectPatient/p-041nothing: Kymolog adds it from the device's assignment
Fig. 2. A CGM sensor sends a number, a unit and a time. Kymolog files it as a FHIR R4 Observation coded LOINC 99504-3, glucose in interstitial fluid, with the UCUM unit mg/dL, the device and the patient attached.

CGM data into the EHR

On an insulin protocol, a nurse reads the CGM receiver every hour and types the value into the flowsheet. With Kymolog, each reading reaches the patient's flowsheet on its own, at the sensor's measurement time.

CGM integration has the same per-device-type setting as every other class: a hospital sends CGM readings straight to the chart, or holds each one for a nurse to approve first. Readings reach Epic, Oracle Health (Cerner), MEDITECH, athenahealth, eClinicalWorks, NextGen and Veradigm over FHIR R4 or HL7 v2, as each EHR takes them.

The same CGM data into the EHR and for researchOne FHIR R4 Observation, LOINC 99504-3, glucose 142 mg/dL at 08:05 for Patient/p-041 from Device/cgm-7f3a, forks two ways. Into the EHR: a flowsheet row, Glucose (CGM) in mg/dL, with readings 126, 131, 137 and 142 at 07:50, 07:55, 08:00 and 08:05, in the patient's chart at the time the sensor took each one; each reading is sent straight in or held for review first, per device type. For research: a study dataset with one row per reading, each carrying the patient, time, LOINC 99504-3, value, unit mg/dL and device. The 08:05 reading of 142 is shown in red in all three places.OBSERVATIONLOINC 99504-3142 mg/dL08:05:00Patient/p-041Device/cgm-7f3aInto the EHREHR FLOWSHEET07:5007:5508:0008:05Glucose (CGM) mg/dL126131137142in the patient's chart, at the time the sensor took itsent straight in, or held for review first, per device typeFor researchSTUDY DATASETPATIENTTIMELOINCVALUEUNITDEVICEp-04107:5099504-3126mg/dLDevice/cgm-7f3ap-04107:5599504-3131mg/dLDevice/cgm-7f3ap-04108:0099504-3137mg/dLDevice/cgm-7f3ap-04108:0599504-3142mg/dLDevice/cgm-7f3aevery reading kept, each with its code, unit, device and timethe series that time in range, CV and SD are computed from
The same CGM data into the EHR and for researchOne FHIR R4 Observation, LOINC 99504-3, glucose 142 mg/dL at 08:05 for Patient/p-041 from Device/cgm-7f3a, forks two ways. Into the EHR: a flowsheet row, Glucose (CGM) in mg/dL, with readings 126, 131, 137 and 142 at 07:50, 07:55, 08:00 and 08:05, in the patient's chart at the time the sensor took each one; each reading is sent straight in or held for review first, per device type. For research: a study dataset with one row per reading, each carrying the patient, time, LOINC 99504-3, value, unit mg/dL and device. The 08:05 reading of 142 is shown in red in all three places.OBSERVATIONLOINC 99504-3    142 mg/dL08:05:00    Patient/p-041Device/cgm-7f3aInto the EHREHR FLOWSHEET07:5508:0008:05Glucose mg/dL131137142in the patient's chart, atthe time the sensor took itsent straight in, or held forreview first, per device typeFor researchSTUDY DATASETTIMELOINCMG/DLDEVICE07:5099504-3126Device/cgm-7f3a07:5599504-3131Device/cgm-7f3a08:0099504-3137Device/cgm-7f3a08:0599504-3142Device/cgm-7f3aevery reading kept as a row for patientp-041, with its code, unit, device and timethe series that time in range,CV and SD are computed from
Figure 3 as a table
TimeValue (mg/dL)Into the EHRFor research
07:50126flowsheet value, Glucose (CGM)dataset row: p-041, 99504-3, Device/cgm-7f3a
07:55131flowsheet value, Glucose (CGM)dataset row: p-041, 99504-3, Device/cgm-7f3a
08:00137flowsheet value, Glucose (CGM)dataset row: p-041, 99504-3, Device/cgm-7f3a
08:05142flowsheet value, Glucose (CGM)dataset row: p-041, 99504-3, Device/cgm-7f3a
Fig. 3. The EHR files the CGM reading in the patient's flowsheet at the time the sensor took it; the study dataset keeps every reading as a coded row, the series that time in range, CV and SD are computed from.

Name the EHR your wards chart in and how often your sensors report. The demo files a day of CGM readings into a test flowsheet and opens the same series as study rows.

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CGM in the hospital

Bedside monitors find their patient through the bed, and a CGM can too while its patient stays in one bed. An inpatient CGM sensor moves with its patient from the ward to imaging to step-down, though, so Kymolog can file its readings through the sensor's assignment to the patient instead. A nurse sets that assignment once, when the sensor goes on, and ends it when the sensor comes off.

Kymolog then files every glucose value in the patient's current encounter, beside the rest of the hospital record. A reading from a sensor with no current assignment waits for review, marked preliminary, until someone matches it to a patient.

CGM data for research

Kymolog keeps every CGM reading as its own coded record, at the sensor's own interval. Each record carries the value, unit and measurement time, the patient's encounter, and the sensor's unique device identifier (UDI) with its serial.

A CGM dataset built from those records answers the standard questions directly. Time in range, mean glucose, the standard deviation (SD), the coefficient of variation (CV) and the ambulatory glucose profile (AGP) are all arithmetic on the series. Our guide to glycemic variability and the AGP works through each one.

For CGM clinical trials, the UDI on every reading shows which sensor produced which value. When a study also needs the EHR's own data, such as A1C results, diagnoses and medications, we point teams to Clinical Extract.

Request a demo for your CGM program

Tell us where your patients wear CGM sensors and which EHR charts them. We reply within one business day with times to talk. In the demo, a day of sensor readings goes into a test chart and comes back out as dataset rows.

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