FHIR APIs are connections through which other software can read from and write to a hospital's or clinic's health records, in one standard format called FHIR. FHIR stands for Fast Healthcare Interoperability Resources, and it is pronounced "fire". It was created by HL7, an international body that writes standards for health data. An API is a defined way for one program to ask another program for data, or to give it data.
Before FHIR, every connection was built separately. Suppose a hospital used one record system, and a diabetes app wanted its patients' blood sugar results. The app's engineers had to learn that hospital's own data format and build a connection for it. For the next hospital, with a different system, they had to start again. FHIR replaces this with one shared format.
FHIR divides health data into small, standard pieces called resources. A Patient resource holds a person's name, date of birth and ID. An Observation resource holds one measurement, such as a blood sugar result, with its value, its unit, its code and its date. A MedicationRequest resource holds one prescription. Each resource is a short block of text in a common format called JSON, and it is sent over the same secure web connections that websites use. So any developer who knows FHIR can read records from any system that offers a FHIR API.
India uses FHIR for its national health records. Under the Ayushman Bharat Digital Mission (ABDM), hospitals, labs and clinics share records in the FHIR format. Each record is linked to the patient's ABHA number and is shared only with the patient's consent. This national system is a piece of digital public infrastructure, as UPI is for payments.
Consider a woman in Surat with type 2 diabetes, who starts using a diabetes care app. The app asks for her past lab results. She approves the request in her ABHA app, for lab reports from the last two years only. The hospital where she was treated then sends six HbA1c results as FHIR Observation resources. They are encrypted, so that only the app can read them. The app draws a chart: her HbA1c, her average blood sugar over three months, fell from 9.2% to 7.4% over the two years. No one typed in a single number.
Companies that sell FHIR APIs do the hard part for hospitals. Many older hospital systems do not offer FHIR at all. The API company connects to the old system, translates its records into FHIR resources, and offers one clean API to every app. In the United States, government rules now require record systems and insurers to let patients and their apps reach records through FHIR APIs.
FHIR APIs are the main pipes of interoperability. A healthcare data platform uses them to collect records, and medical record retrieval uses them wherever a hospital offers one.