HL7 v2 Data Types Reference

^, repeats by ~, sub-components by &

HL7 data types define how values are structured within segment fields. A single field like PID-3 (Patient Identifier List) contains multiple components (ID number, assigning authority, identifier type) packed into one composite data type (CX). Understanding these data types is essential for parsing and building HL7 messages.

Identification Data Types

CX: Extended Composite ID with Check Digit

Used for patient identifiers, account numbers, and visit numbers.

Found in: PID-3, PID-18, PV1-19, IN1-3

MRN12345^^^MAIN_HOSP^MR

Component	Name	Example	Purpose
CX.1	ID Number	MRN12345	The actual identifier value
CX.2	Check Digit	(empty)	Optional validation digit
CX.3	Check Digit Scheme	(empty)	M10, M11, etc.
CX.4	Assigning Authority	MAIN_HOSP	Organization that issued the ID
CX.5	Identifier Type	MR	Type code: MR, AN, VN, SS, PI

Common CX.5 type codes:

Code	Type	Description
MR	Medical Record Number	Primary patient identifier
AN	Account Number	Billing/financial account
VN	Visit Number	Encounter identifier
SS	Social Security Number	SSN (use cautiously, HIPAA sensitivity)
PI	Patient Internal	Internal system identifier
PT	Patient External	External/cross-system identifier
DL	Driver’s License	State-issued ID
NPI	National Provider ID	Provider NPI number

A composite data type packs several related values into one field. The CX patient identifier looks like a single token, but the caret delimiters split it into ordered, individually labelled components: the ID number, an optional check digit, the authority that issued it, and the identifier type code that says what kind of ID it is.

EI: Entity Identifier

Used for order numbers, document IDs, and equipment identifiers.

Found in: ORC-2, ORC-3, OBR-2, OBR-3, TXA-12

ORD5678^EPIC

Component	Name	Example	Purpose
EI.1	Entity Identifier	ORD5678	The identifier value
EI.2	Namespace ID	EPIC	Assigning application
EI.3	Universal ID	(empty)	OID or UUID (optional)
EI.4	Universal ID Type	(empty)	ISO, UUID, DNS (optional)

Person and Name Data Types

XPN: Extended Person Name

Used for patient, contact, and guarantor names.

Found in: PID-5, NK1-2, GT1-3, IN1-16

DOE^JOHN^ALEXANDER^JR^DR^MD

Component	Name	Example	Purpose
XPN.1	Family Name	DOE	Last name
XPN.2	Given Name	JOHN	First name
XPN.3	Second Name	ALEXANDER	Middle name
XPN.4	Suffix	JR	Jr., Sr., III
XPN.5	Prefix	DR	Title prefix
XPN.6	Degree	MD	Academic/professional degree
XPN.7	Name Type	L	L (Legal), D (Display), M (Maiden), A (Alias)

Patient and provider names pack family, given, middle, generation suffix (Jr/Sr), and prefix or title into one caret-delimited XPN field. Additional components (degree, name type, valid-from / to) extend the same pattern.

XCN: Extended Composite ID Number and Name

Used for provider identification: combines an ID with a name.

Found in: PV1-7, PV1-8, ORC-12, OBR-16, EVN-5

ATT1234^SMITH^JANE^^^DR^MD

Component	Name	Example	Purpose
XCN.1	Person Identifier	ATT1234	Provider ID (NPI or local)
XCN.2	Family Name	SMITH	Last name
XCN.3	Given Name	JANE	First name
XCN.4	Second Name	(empty)	Middle name
XCN.5	Suffix	(empty)	Jr., Sr.
XCN.6	Prefix	DR	Title (e.g., Dr.)
XCN.7	Degree	MD	Academic/professional degree
XCN.9	Assigning Authority	(empty)	Organization that assigned the ID
XCN.13	Identifier Type Code	(empty)	NPI, UPIN, local

Address and Contact Data Types

XAD: Extended Address

Used for patient, contact, and facility addresses.

Found in: PID-11, NK1-4, IN1-5, IN1-19

123 MAIN ST^^ANYTOWN^OH^44101^USA

Component	Name	Example	Purpose
XAD.1	Street Address	123 MAIN ST	Street line 1
XAD.2	Other Designation	(empty)	Apt, Suite, Floor
XAD.3	City	ANYTOWN	City name
XAD.4	State	OH	State/province
XAD.5	Zip Code	44101	Postal code
XAD.6	Country	USA	ISO 3166 country code
XAD.7	Address Type	H	H (Home), B (Business), M (Mailing)

A patient or guarantor address packs street, an optional second line (apt or suite), city, state, ZIP, country, and address type into one XAD field. The doubled caret here is the apt/suite slot left empty. Positional gaps are valid and simply mean no value for that component.

XTN: Extended Telecommunication Number

Used for phone numbers, fax, email, and other contact methods.

Found in: PID-13, PID-14, NK1-5, NK1-6

^PRN^PH^^^^^555-867-5309

Component	Name	Example	Purpose
XTN.1	Telephone Number	(deprecated)	Legacy format, use XTN.12
XTN.2	Use Code	PRN	PRN (Primary Residence), WPN (Work), EMR (Emergency)
XTN.3	Equipment Type	PH	PH (Phone), FX (Fax), CP (Cell), Internet (Email)
XTN.4	Communication Address	(empty)	Email address (when XTN.3 = Internet)
XTN.7	Local Number	555-867-5309	Phone number (or XTN.12 in newer versions)
XTN.12	Unformatted Number	5558675309	Full number without formatting

Coded Data Types

CE: Coded Element

The most widely used coded data type in HL7 v2. Carries a code, description, and coding system identifier.

Found in: PID-10, OBR-4, OBX-3, DG1-3, AL1-3

R50.9^Fever, unspecified^I10

Component	Name	Example	Purpose
CE.1	Identifier	R50.9	Code value
CE.2	Text	Fever, unspecified	Human-readable description
CE.3	Coding System	I10	Which coding system (ICD-10, LOINC, SNOMED, etc.)
CE.4	Alternate Identifier	(empty)	Alternate code
CE.5	Alternate Text	(empty)	Alternate description
CE.6	Alternate Coding System	(empty)	Alternate coding system

CWE: Coded With Exceptions

Introduced in v2.5 as a replacement for CE. Identical structure but supports “text only” entries when no code is available.

Found in: OBX-3 (v2.5+), ORC-16, many v2.5+ fields

The key difference: CWE allows CE.1 to be empty when CE.2 contains free text, useful when a coded value doesn’t exist in the coding system.

Coded values carry both a primary code (here ICD-9 250.00) and a parallel alternate from a second coding system (ICD-10 E11.9), so receivers can map between vocabularies in one round trip. Either side can be omitted; CWE additionally allows the primary code to be empty when the text component carries a free-text description.

IS vs ID: Coded Values

Type	Source	Description
IS	User-defined table	Facility-specific codes (e.g., PV1-2 patient class values)
ID	HL7-defined table	Standard HL7 codes (e.g., MSH-11 processing ID: P, T, D)

IS values vary between implementations; ID values are standardized across all HL7 systems.

Date/Time Data Types

TS: Timestamp

The standard date/time format in HL7 v2.

Found in: MSH-7, PID-7, EVN-2, OBR-7, OBR-22

20260301143000-0500

Precision	Format	Example	Meaning
Year	YYYY	2026	Year only
Month	YYYYMM	202603	March 2026
Day	YYYYMMDD	20260301	March 1, 2026
Hour	YYYYMMDDHH	2026030114	2:00 PM
Minute	YYYYMMDDHHMI	202603011430	2:30 PM
Second	YYYYMMDDHHMMSS	20260301143000	2:30:00 PM
Timezone	+/-HHMM suffix	-0500	EST (UTC-5)

Common pitfall: Some systems send timestamps without timezone offsets. Receiving systems should default to the sending facility’s timezone when no offset is present.

HL7 v2 timestamps build precision left-to-right: a 4-digit year, then optional month, day, hour, minute, second, and a trailing ±HHMM timezone offset. Receivers infer the resolution from the string length, so a 4-character value means year-only and a 19-character value means full second-precision with timezone.

DR: Date/Time Range

A pair of TS values representing a range.

Found in: FT1-4, IN1-12/13 (as separate DT fields)

20260301140000^20260301150000

Component 1 is the range start; component 2 is the range end.

Location Data Types

PL: Person Location

Structures the patient’s physical location in a facility.

Found in: PV1-3, PV1-6, PV1-11, PV1-42

ICU^0101^01^MAIN_HOSP^^^^NURS

Component	Name	Example	Purpose
PL.1	Point of Care	ICU	Unit/department/ward
PL.2	Room	0101	Room number
PL.3	Bed	01	Bed number
PL.4	Facility	MAIN_HOSP	Facility identifier
PL.5	Location Status	(empty)	Active, inactive
PL.6	Person Location Type	(empty)	C (Clinic), D (Department), N (Nursing)
PL.7	Building	(empty)	Building code
PL.8	Floor	NURS	Floor/nursing station

A patient location nests from the outside in: the facility contains units (point of care), and each unit contains rooms and beds. PV1-3 carries this composite for the current encounter; PV1-6 carries the prior location.

HD: Hierarchic Designator

Identifies an application, facility, or other entity in a hierarchy.

Found in: MSH-3, MSH-4, MSH-5, MSH-6

EPIC^1.2.3.4.5^ISO

Component	Name	Example	Purpose
HD.1	Namespace ID	EPIC	Application/facility name
HD.2	Universal ID	1.2.3.4.5	OID for the application
HD.3	Universal ID Type	ISO	OID type (ISO, UUID, DNS)

An HD identifies an application or facility with a local namespace name (EPIC) backed by a globally-unique stable identifier: typically an ISO OID, UUID, or DNS name. Receivers can route on the human-readable namespace and fall back to the universal ID for cross-system lookups.

Other Common Types

Type	Name	Description	Example
ST	String	Free text, no formatting	`Patient reported nausea`
NM	Numeric	Numeric value	`98`
SI	Sequence ID	Integer sequence number	`1`, `2`, `3`
FT	Formatted Text	Text with HL7 escape sequences	`Line 1\.br\Line 2`
TX	Text Data	Long free text	Clinical note content
TQ	Timing/Quantity	Schedule timing (deprecated in v2.5+, use TQ1)	`^^30^202603011400^202603011430`
CP	Composite Price	Amount with currency	`350.00^USD`

Key Implementation Considerations

Component Separator Rules

HL7 v2 uses three levels of separation within fields:

Level	Character	Purpose	Example
Field	`\|` (pipe)	Separates segment fields	`PID\|1\|...\|DOE^JOHN`
Component	`^` (caret)	Separates components within a field	`DOE^JOHN^ALEXANDER`
Sub-component	`&` (ampersand)	Separates sub-components within a component	`MAIN_HOSP&1.2.3&ISO`
Repetition	`~` (tilde)	Separates repeated values	`MRN12345~SSN98765`

These characters are defined in MSH-2 and should be read dynamically, not hardcoded.

Null vs Empty Fields

HL7 v2 distinguishes between empty fields and explicitly null fields:

Representation	Meaning	Action
`\|\|`	Empty/not valued	Do not update the stored value
`\|""\|`	Explicitly null	Clear/delete the stored value

This distinction is critical for ADT^A08 (Update Patient) messages: an empty field means “no change” while "" means “remove the previous value.”

Version Compatibility

Many data types were expanded or replaced across HL7 versions:

v2.3	v2.5+	Change
CE	CWE	Added “exceptions” support
TQ	TQ1 segment	Moved from field to segment
XTN.1	XTN.12	Phone number field relocated
CM	Various	Generic CM replaced with specific types

When integrating systems on different HL7 versions, the integration engine should map between data type versions as part of message transformation.

MSH Segment Reference MSH-2 defines the encoding characters that separate components and sub-components within data types.

HL7 v2 Encoding & Delimiters The segment, field, and component hierarchy, and the delimiters that separate the components of every data type.

MLLP Transport Reference Minimum Lower Layer Protocol: the TCP framing that carries messages built from these data types between systems.

HL7 Workbench Parse and validate HL7 messages with segment highlighting and field lookup.

HL7 Resource Center Complete HL7 v2 reference documentation: message types, segments, and sample messages.