HL7 v2 in 10 Minutes

HL7 v2 is a healthcare messaging standard used to exchange information between healthcare systems.

HL7 v2 messages may be used when:

• a patient is admitted to a hospital
• a patient is transferred to another unit
• a lab test is ordered
• a lab result is sent back to the electronic health record
• patient demographic information is updated

Think of HL7 v2 as a structured text message that one healthcare system sends to another.

System A registration, lab, or hospital system

->

HL7 v2 structured text sent between systems

->

System B EHR, clinic system, or downstream app

Each line in an HL7 v2 message is called a segment.

The first three letters of each line are the Segment ID.

Common Segments

A field is one piece of information inside a segment.

Fields are separated by the pipe symbol:

|

Example: MSH Segment

MSH|^~\&|REG|HOSPITAL|EHR|CLINIC|202606151030||ADT^A01|MSG00001|P|2.5.1

MSH Field Breakdown

This means:

The message was sent from REG at HOSPITAL.
The message was sent to EHR at CLINIC.
The message type is ADT^A01.
The message ID is MSG00001.
The HL7 version is 2.5.1.

HL7 v2 uses symbols called delimiters to separate information.

The most important delimiter is:

| = field separator

Example

PID|1||123456^^^HOSPITAL^MR||DOE^JANE||19800115|F

Each | separates one field from the next.

Common HL7 v2 Delimiters

Use this sample message:

This is a simulated message and does not contain real patient information.

Step 1: Identify the Segments

Each line starts with a three-letter segment ID.

Step 2: Read the Message Header

Look at the MSH segment:

MSH|^~\&|REG|HOSPITAL|EHR|CLINIC|202606151030||ADT^A01|MSG00001|P|2.5.1

Step 3: Read the Patient Information

Look at the PID segment:

PID|1||123456^^^HOSPITAL^MR||DOE^JANE||19800115|F

This tells us:

The patient is Jane Doe.
The patient ID is 123456.
The date of birth is 1980-01-15.
The administrative sex is Female.

Step 4: Read the Visit Information

Look at the PV1 segment:

PV1|1|I|4N^402^1||||12345^SMITH^JOHN

This tells us:

The patient is an inpatient.
The location is 4N, room 402, bed 1.
The attending doctor is John Smith.

Use the simulated HL7 v2 message below. You can paste this sample into an HL7 viewer and use an HL7 field definition reference to complete the blanks.

This guide is only a starting point. To build deeper knowledge, use reliable references.

Choose the HL7 version
-> Search the segment ID
-> Open the field list
-> Match the field number

Do not paste real patient information into public online tools.