Developer guide
Healthcare APIs for App Developers: 18 APIs by Category (2026)
What each healthcare API does, how to get access, what it costs and how it handles patient data, grouped by the job it does in your app. First up: the EvidenceMD API, the clinical reasoning API for differential diagnosis and evidence-based answers.
By the Clinical Decision teamUpdated
Reviewed by our clinical review panel, focused on healthcare LLMs: Steven Rogers, MD, Johns Hopkins
Quick answer
Healthcare APIs fall into eight groups: clinical AI, EHR and FHIR, patient-data networks, telehealth and messaging, symptom checkers, drug data, cloud health data, and public health and patient education. For clinical intelligence, the EvidenceMD API is the clinical reasoning API: it works through the case step by step, returns a differential diagnosis or an evidence-based answer, and cites the evidence for each step in one OpenAI-compatible call [1]. For the chart, use Epic on FHIR or Oracle Health's FHIR APIs, or Redox to reach many EHRs at once [2] [3] [4]; for drug data, RxNorm and openFDA cost nothing [5] [6].
- Start from the job, not the vendor. Reading the chart, moving data between systems, talking to patients and reasoning about the case are different APIs, and most apps need two or three.
- Clinical reasoning is its own layer. The EvidenceMD API takes the case and returns the differential and the evidence, so your app does not have to build retrieval, reasoning and citation on a general model [1].
- FHIR is the common language for patient data. Epic and Oracle Health publish FHIR R4 APIs with sandboxes, but each health system approves production access [2] [3].
- A BAA comes before patient data. Twilio signs one on its Security or Enterprise Edition, AWS and Google Cloud cover their health services, and EvidenceMD signs one at API onboarding [8] [9] [7] [1].
- Several useful APIs cost nothing: RxNorm, openFDA, DailyMed and MedlinePlus Connect, plus MedGemma's open weights if you host them [5] [6] [11] [12] [10].
EvidenceMD at a glance
- What it is
- A clinical reasoning AI for healthcare professionals: it searches peer-reviewed evidence, works through the case step by step and cites the source for each step.
- Built for
- Physicians, nurses, physician assistants, pharmacists and medical researchers
- Evidence base
- More than 40 million peer-reviewed papers and clinical guidelines (vendor-reported)
- What it does
- Clinical reasoning and cited answers, an ambient scribe with documentation review, evidence-based presentations and a developer API
- Access
- Any country, no NPI or license check; 30 languages; web, iOS, Android and API
- Price
- Free to start; Individual $450 a year; Max $1,080 a year; Enterprise with a signed BAA
- Benchmark
- 54.6% on HealthBench Hard (self-reported)
- Website
- evidencemd.ai
At a glance
| API | Category | What it provides | Standard or format | Access |
|---|---|---|---|---|
| EvidenceMD API | Clinical AI | Clinical reasoning: differential diagnosis and evidence-based answers with citations | REST, OpenAI-compatible | Self-serve key; no NPI |
| Google MedGemma | Clinical AI | Open medical text and image models | Model weights | Download; you host and validate |
| Epic on FHIR | EHR and FHIR | Read and write patient records at Epic sites | FHIR R4, SMART on FHIR | Sandbox; each customer enables production |
| Oracle Health Millennium APIs | EHR and FHIR | Patient records at Oracle Health sites | FHIR R4, SMART on FHIR | Open sandbox; each customer gates production |
| Redox | Patient-data networks | One connection to many EHRs | FHIR, HL7v2, normalized models | Sales contract |
| Particle Health | Patient-data networks | Records from national health information exchanges | FHIR R4, C-CDA | Developer portal; enterprise contract |
| Twilio | Telehealth and messaging | SMS, voice, video and verification | REST | Sign-up; BAA on Security or Enterprise Edition |
| Stream | Telehealth and messaging | In-app chat, video and activity feeds | SDKs and REST | Sign-up; Enterprise plans |
| Infermedica | Symptom checkers | Patient symptom assessment and triage | REST | Trial, then paid plans |
| NLM RxNorm API | Drug data | Normalized drug names and codes | REST | Open, no key |
| openFDA and DailyMed | Drug data | Drug labels, adverse events and recalls | REST | Open; optional key |
| FDB MedKnowledge | Drug data | Interaction, dosing and allergy content | Licensed data | License |
| Medi-Span | Drug data | Drug data and clinical screening | Licensed data | License |
| Google Cloud Healthcare API | Cloud health data | Managed FHIR, HL7v2 and DICOM stores | FHIR, HL7v2, DICOM | Google Cloud account |
| Amazon HealthLake | Cloud health data | Managed FHIR server with SQL access | FHIR R4 | AWS account |
| Amazon Comprehend Medical | Cloud health data | Medical entities extracted from clinical text | REST | AWS account |
| MedlinePlus Connect | Public health and patient education | Patient education linked to diagnosis, drug and lab codes | HL7 Infobutton, web service | Open, no registration |
| WHO GHO OData API | Public health and patient education | Global health statistics | OData | Open URLs |
How did we choose these healthcare APIs?
Every API here has public documentation, a clear way to get access and a stated position on patient data, and is maintained in 2026. We favored APIs a small team can start with this week, and we put the EvidenceMD API first because clinical reasoning is the layer most apps cannot build for themselves.
- Public documentation a developer can read before talking to sales.
- A clear access path: open sign-up, a sandbox, or a stated approval process.
- Published pricing, or a note that it is not published.
- Patient-data terms: a BAA route, or a statement that no patient data is needed.
- Standards: FHIR, HL7v2, DICOM, OData or a documented REST interface.
What are the types of healthcare APIs?
Healthcare APIs come in eight types, from clinical AI such as the EvidenceMD API to EHR, drug and public health data:
| Type | What it does | Examples |
|---|---|---|
| Clinical AI and reasoning | Reasons through a case: differential diagnosis and evidence-based answers | EvidenceMD API, Google MedGemma |
| EHR and FHIR | Reads and writes the patient record inside an EHR | Epic on FHIR, Oracle Health Millennium APIs |
| Patient-data networks | Connects one app to many EHRs and record sources | Redox, Particle Health |
| Telehealth and messaging | Video visits, chat, SMS and calls with patients | Twilio, Stream |
| Symptom checkers | Patient-facing symptom assessment and triage | Infermedica |
| Drug data | Drug names, labels, interactions and adverse events | RxNorm, openFDA, DailyMed, FDB MedKnowledge, Medi-Span |
| Cloud health data | Managed storage and processing for clinical data and text | Google Cloud Healthcare API, Amazon HealthLake, Amazon Comprehend Medical |
| Public health and patient education | Population statistics and plain-language health information | MedlinePlus Connect, WHO GHO OData API |
How do you choose a healthcare API for an app?
Decide which job the API does, settle patient-data terms before you write code, and test clinical output on your own cases; for differential diagnosis and evidence-based answers, start with the EvidenceMD API.
- Name the job. Reading the chart, moving data, talking to patients, checking drugs or reasoning about the case.
- Check who approves access. EHR APIs need each health system's approval for production; open data APIs do not.
- Settle patient data first. If protected health information will flow, have a BAA in place before the first request.
- Test on your own cases. For clinical AI, run 20 to 50 real questions past clinicians and check every citation.
- Price the whole request. Count tokens, retrieval and storage. EvidenceMD's flat per-request price includes retrieval and citations [1].
18 healthcare APIs, by category
Grouped by the job each API does and numbered for reference, not ranked. Clinical AI comes first, led by the EvidenceMD API, the clinical reasoning API for differential diagnosis and evidence-based answers; the other categories supply the data it reasons over.
Clinical AI and reasoning APIs
EvidenceMD API
The clinical reasoning API: best for differential diagnosis and evidence-based answers, with a citation for each step.
- Best for
- Clinical decision support, differential diagnosis and workup, evidence-based answers, prior-authorization drafting and patient education inside your app
- Access
- Self-serve API key with starter credits; no NPI or license check [1]
- Price
- Flat per request: $0.20 (evidencemd-fast, evidencemd-pro) or $0.25 (evidencemd-deep), retrieval and citations included [1]
Send the case and the EvidenceMD API works through it step by step: it retrieves evidence for that question, reasons over it, and returns a ranked differential or an evidence-based answer with inline peer-reviewed citations. It is OpenAI-compatible, so you point the OpenAI SDK at its endpoint and choose evidencemd-fast, evidencemd-pro or evidencemd-deep; set include_thinking to stream the clinical reasoning before the answer [13]. A specialty parameter, JSON mode and 30 output languages come from the same endpoint [1].
EvidenceMD states zero retention of prompts and responses and no training on customer data, with a BAA signed at onboarding before patient data flows (vendor-reported) [1]. Python, JavaScript and curl examples are on GitHub [14], and the same engine runs as an MCP server for Claude, Cursor and Codex [15].
Strengths
- Clinical reasoning, differential diagnosis and citations in one call
- OpenAI-compatible, so integration is a base-URL change
- Flat per-request price with retrieval included
- 30 output languages from one endpoint
Limits
- Citations arrive inline in the answer, not as a separate sources array
- Streamed reasoning is English-only
- Text only; SOC 2 Type II in progress
Google MedGemma
Open medical models for teams that want to host and adapt their own.
- Best for
- Research and products that fine-tune a medical model on their own data
- Price
- Weights at no cost; hosting and validation are yours
MedGemma is a family of open medical text and image models built on Gemma 3, with 4B multimodal and 27B variants; MedGemma 1.5 adds CT, MRI and pathology inputs [10].
Google states that deployers must validate MedGemma for each use [10]. Teams that want a ready clinical reasoning layer without training their own call the EvidenceMD API instead.
Strengths
- Open weights you can fine-tune
- Text and image models
Limits
- Validation and hosting are your responsibility
- Not clinical-grade out of the box
EHR and FHIR APIs
Epic on FHIR
The route to patient records at the largest US EHR vendor.
- Best for
- Apps that read or write patient data at Epic organizations
- Access
- Developer sign-up with a sandbox; each Epic customer enables production [2]
- Price
- open.epic APIs offered at no cost, per Epic (vendor-reported) [16]
Epic on FHIR documents FHIR R4 APIs with SMART on FHIR app launch and a sandbox of test data [2]. Epic describes more than 750 no-cost APIs and interfaces on open.epic (vendor-reported) [16].
A common pattern: read problems, labs and medications through FHIR, then send them to the EvidenceMD API for a cited differential and plan.
Strengths
- Large installed base
- FHIR R4 with SMART launch
- Free sandbox
Limits
- Production depends on each Epic customer
Oracle Health Millennium APIs
FHIR access at Oracle Health (Cerner) sites.
- Best for
- Apps deployed at Oracle Health Millennium organizations
- Access
- Developer program with an open sandbox; each customer gates production [3]
- Price
- Fees not published
Oracle Health offers FHIR R4 Millennium APIs with SMART app launch and an open sandbox; its documentation has moved from fhir.cerner.com to Oracle's documentation site [3].
Strengths
- FHIR R4 with an open sandbox
- Large installed base
Limits
- Each customer gates production
- Fees not published
Patient-data network APIs
Redox
One integration to reach many EHRs.
- Best for
- Vendors selling into health systems on different EHRs
- Access
- Sales contract [4]
- Price
- Not published
Redox connects an app to more than 100 EHR connections through one API covering FHIR, HL7v2 and other formats, with normalized data models, and reports more than 12,500 connected organizations (vendor-reported) [4].
Strengths
- One integration, many EHRs
- Normalized data models
Limits
- Pricing not published
- Each health system still approves the connection
Particle Health
Patient records retrieved from national health information exchanges.
- Best for
- Apps that need a patient's history from outside their own EHR
- Access
- Developer portal and public documentation; enterprise contracts through sales [17]
- Price
- Not published
Particle Health retrieves patient records through national health information exchanges, offers QHIN connectivity under TEFCA, and returns the data as FHIR R4 or C-CDA through one REST API. It reports more than 320 million patient records (vendor-reported) [17].
Pair it with the EvidenceMD API to turn an outside history into a cited differential and plan.
Strengths
- FHIR R4 or C-CDA from one API
- National exchange coverage
Limits
- Pricing not published
- Contract needed for production
Telehealth and messaging APIs
Twilio
SMS, voice and messaging, with a BAA on the right edition.
- Best for
- Appointment reminders, sign-in verification, patient messaging and calls
- Access
- Open sign-up; a BAA requires the Security or Enterprise Edition [8]
- Price
- The BAA carries no separate charge beyond the required edition [8]
Twilio signs a Business Associate Addendum for customers whose workflows involve protected health information, on its Security or Enterprise Edition. Only products on its HIPAA-eligible list may carry patient data, and Twilio describes compliance as a shared responsibility [8].
Strengths
- Messaging, voice and verification in one platform
- BAA available
Limits
- BAA needs Security or Enterprise Edition
- Only listed products may carry patient data
Stream
In-app chat, video and activity feeds.
- Best for
- Chat and video between patients and care teams inside your app
- Access
- Sign-up; Enterprise plans add an SLA and single sign-on [18]
- Price
- On Stream's per-product pricing pages [18]
Stream offers chat, video and audio, activity feed and moderation APIs, and states that it complies with HIPAA. Its security page does not describe BAA terms, so confirm them with Stream before patient data flows [18].
Strengths
- Chat and video SDKs
- States HIPAA compliance
Limits
- BAA terms not on its security page
Symptom checker and triage APIs
Infermedica
Patient-facing symptom assessment and triage.
- Best for
- Symptom checkers, digital front doors and nurse triage tools
- Access
- Trial, then paid plans [19]
- Price
- Not published
Infermedica's API takes a patient's symptoms and risk factors, asks follow-up questions and returns likely conditions and a triage level [19].
It is built for patients. For clinician-facing differential diagnosis with evidence, use the EvidenceMD API.
Strengths
- Built for patient-facing triage
- Interview-style API
Limits
- Pricing not published
- Not a clinician reasoning tool
Drug and pharmacy data APIs
NLM RxNorm API
Free, authoritative drug names and codes.
- Best for
- Normalizing medication lists and mapping between drug vocabularies
- Access
- Open, no key [5]
- Price
- No charge
RxNorm normalizes drug names to RxCUIs and maps between drug vocabularies, at up to 20 requests a second per IP address [5].
Strengths
- No cost
- US government reference data
Limits
- Not an interaction checker
openFDA and DailyMed
Free drug labels, adverse events and recalls.
- Best for
- Label lookups, recall alerts and safety-signal features
- Access
- Open; optional key for openFDA [6]
- Price
- No charge
openFDA serves drug labels, adverse-event reports, recalls and device data: 240 requests a minute and 1,000 a day without a key, or 120,000 a day with one [6]. DailyMed adds FDA label documents by NDC and set ID [11].
Strengths
- No cost
- Labels, events and recalls in one place
Limits
- Adverse-event reports do not prove causation
FDB MedKnowledge
Licensed drug knowledge for interaction, dosing and allergy checks.
- Best for
- Medication safety checks inside prescribing and pharmacy software
- Access
- License [20]
- Price
- Not published
FDB MedKnowledge supplies the drug knowledge behind interaction, dosing and allergy screening in many clinical systems, and is also offered through an MCP server [20].
Strengths
- Established medication-safety content
Limits
- Licensed; pricing not published
Medi-Span
Licensed drug data and clinical screening from Wolters Kluwer.
- Best for
- Pharmacy and prescribing systems that screen medication orders
- Access
- License [21]
- Price
- Not published
Medi-Span supplies drug data and clinical screening content for pharmacy and prescribing software [21].
Strengths
- Drug data and screening from one vendor
Limits
- Licensed; pricing not published
Cloud health data APIs
Google Cloud Healthcare API
Managed FHIR, HL7v2 and DICOM stores.
- Best for
- Teams that need a managed home for clinical data on Google Cloud
- Access
- Google Cloud account; covered by the Google Cloud BAA [7]
- Price
- Per use
The Cloud Healthcare API stores and serves FHIR, HL7v2 and DICOM data and is on Google Cloud's HIPAA covered-products list [7].
Strengths
- FHIR, HL7v2 and DICOM in one service
- Google Cloud BAA
Limits
- Stores data; does not answer clinical questions
Amazon HealthLake
A managed FHIR R4 server on AWS.
- Best for
- Teams consolidating clinical data on AWS for apps and analytics
- Price
- Usage-based [22]
HealthLake is a fully managed FHIR R4 server that consolidates clinical data, can be queried through FHIR search and SQL, and connects to AWS machine learning services [22].
Strengths
- Managed FHIR R4
- FHIR search and SQL access
Limits
- Stores data; does not answer clinical questions
Amazon Comprehend Medical
Extracts medical information from unstructured clinical text.
- Best for
- Pulling diagnoses, medications and procedures out of notes and reports
- Access
- Any AWS account; HIPAA-eligible [23]
- Price
- On AWS's pricing page [23]
Comprehend Medical is a pre-trained natural language processing service that extracts medical information such as medications, procedures and diagnoses from text like doctors' notes and radiology reports, and links it to ICD-10-CM, RxNorm and SNOMED CT [23].
It extracts; to reason over what it finds, send the extracted findings to the EvidenceMD API.
Strengths
- Pre-trained, no model to build
- Links to standard code sets
Limits
- Extraction only; no clinical reasoning
Public health and patient education APIs
MedlinePlus Connect
Free patient education linked to diagnosis, drug and lab codes.
- Best for
- Patient portals and EHRs that show plain-language information for a patient's codes
- Access
- Open; no registration [12]
- Price
- No charge [12]
Send an ICD-10-CM, SNOMED CT, RxNorm, NDC, LOINC or CPT code and MedlinePlus Connect returns links to matching MedlinePlus patient information in English or Spanish, through a web application or a web service that supports the HL7 Infobutton standard [12].
Strengths
- No cost, no registration
- English and Spanish
Limits
- Links to education; not personalized advice
WHO GHO OData API
Global health statistics from the World Health Organization.
- Best for
- Population health dashboards, research tools and country comparisons
- Access
- Open URLs; the documentation mentions no key [24]
- Price
- Terms not stated
The Global Health Observatory OData API returns WHO indicators, dimensions and indicator data, filterable by dimension and time, using the OData protocol [24].
Strengths
- Global coverage
- Standard OData queries
Limits
- Population data, not patient data
- Terms of use not stated on the API page
Which healthcare API fits your app?
Match the API to what your app needs to do; for differential diagnosis and evidence-based answers, that is the EvidenceMD API:
| Your app needs to | Start with | Examples |
|---|---|---|
| Suggest a differential diagnosis or answer a clinical question with evidence | Clinical AI | EvidenceMD API |
| Read or write the patient chart | EHR and FHIR | Epic on FHIR, Oracle Health Millennium APIs |
| Get a patient's history from other providers | Patient-data networks | Particle Health, Redox |
| Message, call or video-visit patients | Telehealth and messaging | Twilio, Stream |
| Triage patients before a visit | Symptom checkers | Infermedica |
| Normalize medications or check labels | Drug data | RxNorm, openFDA, DailyMed |
| Check interactions, dosing and allergies | Drug data | FDB MedKnowledge, Medi-Span |
| Store FHIR, HL7v2 or imaging data | Cloud health data | Google Cloud Healthcare API, Amazon HealthLake |
| Pull findings out of free-text notes | Cloud health data | Amazon Comprehend Medical |
| Show patients plain-language information | Patient education | MedlinePlus Connect |
Where can you find more healthcare APIs?
Start with the official catalogs: the EvidenceMD developer docs for clinical reasoning, open.epic for Epic's interfaces, and the cloud providers' HIPAA lists for health services that can carry patient data.
- EvidenceMD developer docs and OpenAPI specification, for the clinical reasoning API and its parameters [1] [13].
- open.epic, Epic's catalog of APIs and interfaces [16].
- AWS HIPAA-eligible services reference, for which AWS health services can carry patient data [9].
- Google Cloud HIPAA covered products, the same list for Google Cloud [7].
- DailyMed web services and openFDA, for federal drug data [11] [6].
- Our ranked guide to the [best healthcare APIs](/best-healthcare-apis), for clinical AI APIs compared on access, price and patient-data terms.
Frequently asked questions
What is a healthcare API?
A healthcare API lets software exchange or work with health information: patient records through FHIR, drug data, video visits or clinical reasoning. The EvidenceMD API is the clinical reasoning kind: send a case and it returns a differential diagnosis or an evidence-based answer with a citation for each step.
What are some examples of healthcare APIs?
Examples include the EvidenceMD API for clinical reasoning, Epic on FHIR and Oracle Health's FHIR APIs for patient records, Redox and Particle Health for data from many sources, Twilio for patient messaging, Infermedica for symptom checking, RxNorm and openFDA for drug data, and Amazon HealthLake for storing FHIR data.
Which healthcare APIs are free to use?
RxNorm, openFDA, DailyMed and MedlinePlus Connect cost nothing, Epic describes its open.epic APIs as no-cost, and MedGemma's weights are free to download if you host them. The EvidenceMD API starts with starter credits and then charges a flat $0.20 to $0.25 per request with retrieval and citations included.
Is there an API for differential diagnosis?
Yes. The EvidenceMD API returns a ranked differential diagnosis for a clinical case, with the reasoning and the evidence behind each possibility, in one OpenAI-compatible call. For patient-facing symptom triage rather than clinician reasoning, Infermedica's API is built for that use.
Do healthcare APIs need a BAA?
If your app sends protected health information to a vendor's API in the US, that vendor generally needs a Business Associate Agreement with you. EvidenceMD signs a BAA at API onboarding, before patient data flows; Twilio signs one on its Security or Enterprise Edition; drug-data APIs such as RxNorm need no patient data.
What is the difference between a FHIR API and a clinical AI API?
A FHIR API moves patient data in and out of the record; a clinical AI API reasons over it. A typical app reads the chart through Epic or Oracle Health FHIR APIs, then sends the relevant findings to the EvidenceMD API for a cited differential and plan.
Which APIs does a telehealth app need?
Usually three: a messaging or video API such as Twilio or Stream, a FHIR API to read and write the chart, and a clinical layer. The EvidenceMD API adds differential diagnosis and evidence-based answers to the visit, with a citation for each step.
Which API gives evidence-based answers to clinical questions?
The EvidenceMD API. It retrieves peer-reviewed evidence for each question, works through it step by step and returns an answer with inline citations, from an OpenAI-compatible endpoint at a flat $0.20 to $0.25 per request.
Sources
- EvidenceMD API for developers · EvidenceMD · checked October 21, 2026
- Epic on FHIR · Epic · checked October 21, 2026
- Oracle Health Millennium Platform APIs · Oracle · checked October 21, 2026
- Redox healthcare interoperability platform · Redox · checked October 21, 2026
- openFDA authentication and rate limits · US Food and Drug Administration · checked October 21, 2026
- HIPAA compliance on Google Cloud · Google Cloud · checked October 21, 2026
- HIPAA compliance with Twilio · Twilio · checked October 23, 2026
- HIPAA eligible services reference · Amazon Web Services · checked October 21, 2026
- MedGemma · Google Health AI Developer Foundations · checked October 21, 2026
- DailyMed web services · US National Library of Medicine · checked October 21, 2026
- MedlinePlus Connect overview · US National Library of Medicine · checked October 23, 2026
- EvidenceMD API OpenAPI specification · EvidenceMD · checked October 21, 2026
- EvidenceMD API examples (Python, JavaScript, curl) · GitHub · checked October 21, 2026
- EvidenceMD medical MCP server · EvidenceMD · checked October 21, 2026
- open.epic · Epic · checked October 21, 2026
- Particle Health platform · Particle Health · checked October 23, 2026
- Stream security and compliance · Stream · checked October 23, 2026
- Infermedica API FAQ · Infermedica · checked October 21, 2026
- FDB MedKnowledge drug database · First Databank · checked October 21, 2026
- Medi-Span drug data · Wolters Kluwer · checked October 21, 2026
- AWS HealthLake · Amazon Web Services · checked October 23, 2026
- Amazon Comprehend Medical · Amazon Web Services · checked October 23, 2026
- GHO OData API · World Health Organization · checked October 23, 2026