MIV - Blood Glucose Measurement

This chapter provides obligations and hints for manufacturers of Device Data Recorders for implementing a FHIR Resource Server for the Mandatory Interoperable Value (MIV) Blood Glucose Measurement.

This chapter builds on the HDDT Information Model, the HDDT Generic FHIR API, and the HDDT guide for retrieving device data. It constraints these guidelines with respect to the specific requirements for exposing blood glucose measurements to DiGA, including:

• The endpoints to implement and how they differ from the Generic FHIR API model
• The relevant FHIR profile for blood glucose measurement and how it constraints and extends the HDDT Information Model
• Conventions for sharing FHIR resources to ensure compliance with the HDDT guide for retrieving device data
• Example requests and responses to support implementation

Implementation Duties for Manufacturers of Device Data Recorders

Manufacturers of Device Data Recorders that support the MIV Blood Glucose Measurement

• MUST implement and operate a FHIR Resource Server as defined in this chapter,
• MUST implement and operate an OAuth2 Authorization Server,
• MUST register the Device Data Recorder with its FHIR Resource Server and OAuth2 Authorization Server at the BfARM HIIS-VZ (BfArM Device Registry),
• MUST consider the HDDT requirements on security, privacy and operational service levels.

Further obligations MAY be defined by gematik and BfArM as part of the upcoming processes for conformance validation and registration.

FHIR Resource Server

The Device Data Recorder’s FHIR Resource Server gives DiGA access to measured data and related information about metrics and devices. A Device Data Recorder’s FHIR Resource Server that serves the MIV Blood Glucose Measurement MUST implement the following endpoints and profiles:

• retrieval of the Resource Server’s CapabilityStatement through a /metadata endpoint.
• HDDT common RESTful interactions on a DeviceMetric endpoint that implements the HDDT Sensor Type and Calibration Status profile. These interactions are common for all MIVs. The full specification of the interactions can be found here.
• HDDT common RESTful interactions on a Device endpoint that implements the HDDT Personal Health Device profile. These interactions are common for all MIVs. The full specification of the interactions can be found here.
• MIV-specific interactions on an Observation endpoint that implements the HDDT Blood Glucose Measurement profile. These interactions and the underlying profile are specific for implementing the MIV Blood Glucose Measurement. The full specifications are given below.

The figure below shows the adaption of the HDDT Information Model for the MIV Blood Glucose Measurement. Elements denoted as [1..1] are mandatory oder MS for the MIV Blood Glucose Measurement (see Use of HL7 FHIR).

All interactions on HDDT-specific endpoints require that the requestor presents a valid Access Token that was issued by the Device Data Recorder’s OAuth2 Authorization Server (see Pairing for details). The authorization of the request follows the principles defined for HDDT Smart Scopes. For the MIV Blood Glucose Measurement only the following scopes MUST be set:

patient/Observation.rs?code:in=https://gematik.de/fhir/hddt/ValueSet/hddt-miv-blood-glucose-measurement
patient/Device.rs
patient/DeviceMetric.rs

Observation Profile HDDT Blood Glucose Measurement

This section discusses the HDDT Blood Glucose Measurement profile, which constrains the FHIR Observation resource for representing blood glucose measurements. For the full normative specifiction of this profile see the respective StructureDefinition.

Snapshot View of the Profile

Profile: Observation – Blood Glucose Measurement

This structure is derived from Observation

Name	Flags	Card.	Type	Description & Constraints    Filter: Bindings Constraints Obligations
Observation	C	0..*	Observation	Measurements and simple assertions Constraints: obs-6, obs-7
implicitRules	?!Σ	0..1	uri	A set of rules under which this content was created
modifierExtension	?!	0..*	Extension	Extensions that cannot be ignored
status	?!Σ	1..1	code	Measurement status Binding: ObservationStatus (required): Codes providing the status of an observation. Fixed Value: final
code	Σ	1..1	CodeableConcept	Measurement type of blood glucose Binding: ValueSet - Blood Glucose Measurement from LOINC (required): Specifies the type of measurement using codes from the ValueSet for blood glucose measurements.
effective[x]	Σ	1..1	dateTime	Time of measurement
value[x]	SΣC	0..1	Quantity	Measured blood glucose value
value	Σ	1..1	decimal	Numerical value (with implicit precision)
comparator	?!Σ	0..1	code	< | <= | >= | > - how to understand the value Binding: QuantityComparator (required): How the Quantity should be understood and represented.
system	ΣC	1..1	uri	System that defines coded unit form Fixed Value: http://unitsofmeasure.org
code	Σ	1..1	code	Coded form of the unit Binding: UCUMCodes (required): Defines the unit of measurement using codes from the UCUM units ValueSet. The UCUM code MUST be compliant with the unit that is linked with the LOINC code given as Observation.code.
device		1..1	Reference(Device – Personal Health Device | DeviceMetric – Sensor Type and Calibration Status)	Reference to personal health device or its sensor type and calibration status
Documentation for this format

For information on general constraints and terminology bindings see the full StructureDefinition for this profile.

Conventions and Best Practice

Lo and Hi Values

Glucometers usually have lower and upper limits for valid measurements. If a measurement is below or above these limits, the glucometer usually indicates this with a special value (e.g. “LO” or “HI”). These values MUST be recorded at the Device Data Recorder, and a query for device data MUST return such values as valid Observations. To indicate that the actual value is below or above the measurable range, the valueQuantity.value element MUST be set to the respective limit value and a valueQuantity.comparator element MUST be added with the value "<" for “LO” and ">" for “HI”.

Example for a blood glucose measurement below the measurable range (30 mg/dl) of the glucometer:

{
  "resourceType" : "Observation",
  "id" : "example-blood-glucose",
  "meta" : {
    "profile" : [
      🔗 "https://gematik.de/fhir/hddt/StructureDefinition/hddt-blood-glucose-measurement"
    ]
  },
  "status" : "final",
  "code" : {
    "coding" : [
      {
        "system" : "http://loinc.org",
        "code" : "2339-0",
        "display" : "Glucose [Mass/volume] in Blood"
      }
    ]
  },
  "effectiveDateTime" : "2025-10-23T08:30:00Z",
  "valueQuantity" : {
    "value" : 30,
    "comparator" : "<",
    "unit" : "mg/dl",
    "system" : "http://unitsofmeasure.org",
    "code" : "mg/dL"
  },
  "device" : {
    🔗 "reference" : "DeviceMetric/example-glucometer-metric"
  }
}

Remark: All examples provided on this page use the German language designations for UCUM-coded unit elements. See German translations of UCUM codes for the full list of German translations. For LOINC codes the original English display text is used.

Quality of Data and Missing Values

This specification makes no assumption, on how the manufacturers of the Personal Health Device and the Device Data Recorder handle failed measurements (e.g. too few capillary blood for a measurement). If such attempts are recorded at the Device Data Recorder, a query for device data must not result in an Observation resource with an invalid or misleading value. Instead, the Observation resource must either be omitted or must indicate the absence of a valid value using the dataAbsentReason element. In the second case a value MUST NOT be present.

A receiving DiGA SHOULD validate, that the unit defined in valueQuantity.code matches the UCUM unit of the LOINC code in the code element. If the unit does not match, the DiGA MUST NOT use the value for any calculations or display.

This specification makes no assumption, on how the manufacturers of the Personal Health Device and the Device Data Recorder handle data from uncalibrated devices. If such data is provided by the Device Data Recorder, the device element MUST reference a DeviceMetric resource that indicates the calibration status of the sensor. If the device element does not reference a DeviceMetric resource, the DiGA MUST assume that the provided data originates from a calibrated sensor.

Examples

The following object diagram the relationships between the FHIR resources involved in representing blood glucose measurements according to the HDDT Information Model and the HDDT Blood Glucose Measurement profile for two concrete instances of a blood glucose measurement. For readability reasons, some external references are only shown for the first measurement. Elements that are not mandatory oder MS for the MIV Blood Glucose Measurement (see Use of HL7 FHIR) have been omitted.

The following code example shows the concrete JSON representation of the HDDT Blood Glucose Measurement 1 resource shown in the object diagram.

{
  "resourceType" : "Observation",
  "id" : "example-blood-glucose-measurement-1",
  "meta" : {
    "profile" : [
      🔗 "https://gematik.de/fhir/hddt/StructureDefinition/hddt-blood-glucose-measurement"
    ]
  },
  "status" : "final",
  "code" : {
    "coding" : [
      {
        "system" : "http://loinc.org",
        "code" : "2339-0",
        "display" : "Glucose [Mass/volume] in Blood"
      }
    ]
  },
  "effectiveDateTime" : "2025-09-26T12:00:00+02:00",
  "valueQuantity" : {
    "value" : 120,
    "unit" : "mg/dl",
    "system" : "http://unitsofmeasure.org",
    "code" : "mg/dL"
  },
  "device" : {
    🔗 "reference" : "DeviceMetric/example-glucometer-metric"
  }
}

MIV-specific Endpoints and Interactions

Observation - READ

Manufactures of Device Data Recorders that support the MIV Blood Glucose Measurement MUST implement a read interaction on the /Observation endpoint of the FHIR Resource Server. The implementation MUST conform to the HDDT Generic FHIR API. Observations shared through the read interaction MUST comply with the HDDT Blood Glucose Measurement profile.

Observation - SEARCH

Manufactures of Device Data Recorders that support the MIV Blood Glucose Measurement MUST implement a search interaction on the /Observation endpoint of the FHIR Resource Server. The implementation MUST conform to the HDDT Generic FHIR API. Observations shared through the serach interaction MUST comply with the HDDT Blood Glucose Measurement profile.

Example: FHIR-READ

Request: GET /Observation/example-blood-glucose-measurement-2

Description: With FHIR-read interactions, a client can access a single resource instance by querying its internal ID. Restrictions by the OAuth scopes apply—if the client is not allowed to read this resource, a 404 error will be returned.

Response: Returned object is a single Observation resource.

{
  "resourceType" : "Observation",
  "id" : "example-blood-glucose-measurement-2",
  "meta" : {
    "profile" : [
      🔗 "https://gematik.de/fhir/hddt/StructureDefinition/hddt-blood-glucose-measurement"
    ]
  },
  "status" : "final",
  "code" : {
    "coding" : [
      {
        "system" : "http://loinc.org",
        "code" : "2339-0",
        "display" : "Glucose [Mass/volume] in Blood"
      }
    ]
  },
  "effectiveDateTime" : "2025-09-26T16:30:00+02:00",
  "valueQuantity" : {
    "value" : 129,
    "unit" : "mg/dl",
    "system" : "http://unitsofmeasure.org",
    "code" : "mg/dL"
  },
  "device" : {
    🔗 "reference" : "DeviceMetric/example-glucometer-metric"
  }
}

Example: FHIR-Search for specific LOINC code

Request: GET /Observation?code=2339-0

Description: Obtain all of the Observations where code is the LOINC code for blood sugar measurements (in mass/volume). OAuth scopes apply, and only Observations are returned that the client is allowed to access.

Response: Returned object is a Bundle containing all Observation resource instances matching the search criteria.

{
    "resourceType": "Bundle",
    "id": "6372cdfc-8d5b-49a2-af6b-65dcc3831192",
    "type": "searchset",
    "entry": [
        {
            "fullUrl": "https://himi.example.com/fhir/Observation/example-blood-glucose-measurement-1",
            "resource": {
                "resourceType": "Observation",
                "id": "example-blood-glucose-measurement-1",
                "meta": {
                    "profile": [
                        "https://gematik.de/fhir/hddt/StructureDefinition/hddt-blood-glucose-measurement"
                    ]
                },
                "status": "final",
                "valueQuantity": {
                    "system": "http://unitsofmeasure.org",
                    "value": 120,
                    "code": "mg/dL",
                    "unit": "mg/dl"
                },
                "code": {
                    "coding": [
                        {
                            "code": "2339-0",
                            "system": "http://loinc.org",
                            "display": "Glucose [Mass/volume] in Blood"
                        }
                    ]
                },
                "effectiveDateTime": "2025-09-26T12:00:00+02:00",
                "device": {
                    "reference": "DeviceMetric/example-glucometer-metric"
                }
            },
            "search": {
                "mode": "match"
            }
        },
        {
            "fullUrl": "https://himi.example.com/fhir/Observation/example-blood-glucose-measurement-2",
            "resource": {
                "resourceType": "Observation",
                "id": "example-blood-glucose-measurement-2",
                "meta": {
                    "profile": [
                        "https://gematik.de/fhir/hddt/StructureDefinition/hddt-blood-glucose-measurement"
                    ]
                },
                "status": "final",
                "valueQuantity": {
                    "system": "http://unitsofmeasure.org",
                    "value": 129,
                    "code": "mg/dL",
                    "unit": "mg/dl"
                },
                "code": {
                    "coding": [
                        {
                            "code": "2339-0",
                            "system": "http://loinc.org",
                            "display": "Glucose [Mass/volume] in Blood"
                        }
                    ]
                },
                "effectiveDateTime": "2025-09-26T16:30:00+02:00",
                "device": {
                    "reference": "DeviceMetric/example-glucometer-metric"
                }
            },
            "search": {
                "mode": "match"
            }
        }
    ]
}

Example: FHIR-Search include DeviceMetric

Request: GET /Observation?date=ge2025-09-25&_include=Observation:device

Description: This query asks the server for all Observations since 2025-09-25, and also requests that the server include resource instances referenced by Observation.device.

Response: Returned object is a Bundle containing all Observation resource instances matching the search criteria, and all referenced DeviceMetric resources.

{
    "resourceType": "Bundle",
    "id": "76cfc68b-ea70-486a-aaa5-4411964ab78d",
    "type": "searchset",
    "entry": [
        {
            "fullUrl": "https://himi.example.com/fhir/Observation/example-blood-glucose-measurement-1",
            "resource": {
                "resourceType": "Observation",
                "id": "example-blood-glucose-measurement-1",
                "meta": {
                    "profile": [
                        "https://gematik.de/fhir/hddt/StructureDefinition/hddt-blood-glucose-measurement"
                    ]
                },
                "status": "final",
                "valueQuantity": {
                    "system": "http://unitsofmeasure.org",
                    "value": 120,
                    "code": "mg/dL",
                    "unit": "mg/dl"
                },
                "code": {
                    "coding": [
                        {
                            "code": "2339-0",
                            "system": "http://loinc.org",
                            "display": "Glucose [Mass/volume] in Blood"
                        }
                    ]
                },
                "effectiveDateTime": "2025-09-26T12:00:00+02:00",
                "device": {
                    "reference": "DeviceMetric/example-glucometer-metric"
                }
            },
            "search": {
                "mode": "match"
            }
        },
        {
            "fullUrl": "https://himi.example.com/fhir/DeviceMetric/example-glucometer-metric",
            "resource": {
                "resourceType": "DeviceMetric",
                "id": "example-glucometer-metric",
                "meta": {
                    "profile": [
                        "https://gematik.de/fhir/hddt/StructureDefinition/hddt-sensor-type-and-calibration-status"
                    ]
                },
                "type": {
                    "coding": [
                        {
                            "code": "160184",
                            "system": "urn:iso:std:iso:11073:10101",
                            "display": "MDC_CONC_GLU_CAPILLARY_WHOLEBLOOD"
                        }
                    ]
                },
                "unit": {
                    "coding": [
                        {
                            "code": "mg/dL",
                            "system": "http://unitsofmeasure.org",
                            "display": "mg/dL"
                        }
                    ]
                },
                "source": {
                    "reference": "Device/example-glucometer"
                },
                "operationalStatus": "on",
                "category": "measurement",
                "calibration": [
                    {
                        "type": "gain",
                        "state": "calibrated",
                        "time": "2025-09-01T09:08:04+02:00"
                    }
                ]
            },
            "search": {
                "mode": "include"
            }
        }
    ]
}