One Medical FHIR Implementation Guide
0.1.0 - ci-build
One Medical FHIR Implementation Guide - Local Development build (v0.1.0) built by the FHIR (HL7® FHIR® Standard) Build Tools. See the Directory of published versions
FHIR (Fast Healthcare Interoperability Resources) is a standard for exchanging healthcare data. Think of it as a shared schema for medical records — it defines data types like Patient, Condition, Observation, and MedicationRequest so that different systems can exchange clinical data in a consistent format.
This Implementation Guide (IG) documents the specific data shapes that One Medical systems produce and consume. Each profile in this guide is like a TypeScript interface — it defines which fields are present, which are required, what values are allowed, and what the data means.
Each profile page has an intro section at the top (plain English) and FHIR tables below (technical detail). If you're new to FHIR, start with the intro and examples.
Profile pages have several table views. Start with "Key Elements" — it filters out inherited noise and shows only the fields this profile actually constrains.
| Column | What It Means |
|---|---|
| Name | The field name. Nested fields are indented. |
| Flags | S = Must Support (implementers must handle this field). ?! = Modifier (can change the meaning of the resource). |
| Card. | How many times this field can appear: 1..1 = exactly one (required), 0..1 = zero or one (optional), 0..* = any number (optional list), 1..* = at least one (required list). |
| Type | The data type — e.g., string, dateTime, Reference(Patient), CodeableConcept. |
| Description & Constraints | The most useful column. Contains a short description of what the field means, plus any value constraints or bindings. |
Must Support ≠ Required. A Must Support field (S flag) means systems must be able to handle it, but it can still be empty. Required means it's always present (Card. starts with 1).| Term | What It Means |
|---|---|
| Profile | A constrained version of a FHIR resource — defines which fields are used and how. Like a TypeScript interface. |
| Resource | A FHIR data object — Patient, Condition, Observation, etc. |
| Observation | The FHIR resource type for measurements, test results, and assessments (vitals, labs, survey scores). |
| Reference | A pointer to another resource — e.g., Reference(Patient) means this field links to a Patient record. |
| CodeableConcept | A coded value that can include multiple coding systems. For example, a diagnosis might have both an ICD-10 code and a SNOMED code. |
| Binding | Links a field to a set of allowed values (a ValueSet). Binding strength indicates how strictly the values must be followed: required = must use these values, extensible = should use these but can add others. |
| ValueSet | A defined list of allowed coded values — like an enum. |
| CodeSystem | A dictionary of codes with meanings — e.g., SNOMED CT, ICD-10, LOINC. |
| Extension | A custom field added beyond the base FHIR spec. |
| Bundle | A collection of FHIR resources sent together — like a visit summary containing a patient, encounter, conditions, and medications. |
| LOINC | Logical Observation Identifiers Names and Codes — a coding system for lab tests and clinical observations. |
| SNOMED CT | A comprehensive clinical terminology used for diagnoses, procedures, and findings. |
| ICD-10 | International Classification of Diseases — the standard coding system for diagnoses and billing. |
| UCUM | Unified Code for Units of Measure — standardized unit codes (e.g., mg/dL, mmHg, /min). |
| US Core | A US-specific FHIR implementation guide that defines baseline profiles. Many One Medical profiles build on top of US Core. |
| PPV | Pay-Per-Visit — One Medical's model for visit-based data exchange with external payers. |
| VBC | Value-Based Care — data exchange for population health and quality measurement programs. |
| CDP / Aspen | One Medical's internal FHIR server that stores and serves clinical data. Historically called CDP (Clinical Data Platform), now called Aspen. |
| OneLife | One Medical's electronic health record (EHR) system where clinicians document patient care. |