HL7 PID Segment: Patient Identification

The HL7 PID segment (Patient Identification) carries the patient’s demographic and identification data. It appears in virtually every HL7 v2 message type — ADT, ORM, ORU, SIU, DFT, and more. Correct PID mapping is critical for patient matching and record linkage across systems.

What is the HL7 PID segment?

The PID segment is the Patient Identification segment of an HL7 v2 message, identified by the three-letter code PID. It holds up to 39 fields describing who the patient is — identifiers, name, birth date, sex, and address. Its most important field, PID-3, lists every patient identifier with its assigning authority.

PID Field Reference

Seq	Name	Type	Opt	Description
`PID-1`	Set ID	SI	O	Sequence number (usually 1)
`PID-2`	Patient ID (External)	CX	W	Withdrawn in v2.3.1 — use PID-3
`★ PID-3`	Patient Identifier List	CX	R	MRN and all identifiers (repeating)
Primary matching key. Must include assigning authority (CX.4) and identifier type (CX.5). Repeat for multiple identifiers (MRN, EMPI, account number).
`PID-4`	Alternate Patient ID	CX	W	Withdrawn — use PID-3
`★ PID-5`	Patient Name	XPN	R	Family^Given^Middle^Suffix^Prefix
XPN data type. Can repeat for legal name, alias, maiden name. XPN.7 indicates name type (L=Legal, A=Alias, M=Maiden).
`PID-6`	Mother's Maiden Name	XPN	O	Used for identity verification
`★ PID-7`	Date/Time of Birth	TS	O	YYYYMMDD format
Critical for patient matching. Some systems send YYYYMMDDHHMMSS — receiving systems should handle both formats.
`★ PID-8`	Administrative Sex	IS	O	M, F, O, U, A, N
`PID-9`	Patient Alias	XPN	W	Withdrawn in v2.4
`PID-10`	Race	CE	O	HL7 table 0005
`★ PID-11`	Patient Address	XAD	O	Street^City^State^Zip^Country
`PID-12`	County Code	IS	W	Withdrawn — use PID-11
`★ PID-13`	Phone (Home)	XTN	O	Home phone number
`★ PID-14`	Phone (Business)	XTN	O	Work phone number
`PID-15`	Primary Language	CE	O	Preferred language
`PID-16`	Marital Status	CE	O	HL7 table 0002
`PID-17`	Religion	CE	O	HL7 table 0006
`★ PID-18`	Patient Account Number	CX	O	Visit/encounter account
Often used as a secondary matching key. Maps to the encounter/visit-level account in the receiving system.
`PID-19`	SSN (Patient)	ST	W	Withdrawn — use PID-3
Still populated by many legacy systems. Modern implementations should use PID-3 with identifier type SS.
`PID-20`	Driver's License	DLN	W	Withdrawn in v2.5
`PID-21`	Mother's Identifier	CX	O	Links newborn to mother
`PID-22`	Ethnic Group	CE	O	HL7 table 0189
`PID-23`	Birth Place	ST	O	City/state of birth
`PID-24`	Multiple Birth Indicator	ID	O	Y/N for twins, triplets
`PID-25`	Birth Order	NM	O	1, 2, 3 for multiples
`PID-26`	Citizenship	CE	O	Country of citizenship
`PID-27`	Veterans Status	CE	O	Military veteran indicator
`PID-28`	Nationality	CE	W	Withdrawn in v2.4
`PID-29`	Patient Death Date	TS	O	Date and time of death
`PID-30`	Patient Death Indicator	ID	O	Y/N
`PID-31`	Identity Unknown	ID	O	Y if patient cannot be identified
`PID-32`	Identity Reliability	IS	O	AL (alias name), UA (unknown/default address), US (unknown/default SSN), UD (unknown/default DOB)
`PID-33`	Last Update Date	TS	O	When PID data was last modified
`PID-34`	Last Update Facility	HD	O	Facility that last updated the record
`PID-35`	Taxonomic Classification	CE	O	Species code (veterinary)
`PID-36`	Breed Code	CE	O	Breed (veterinary)
`PID-37`	Strain	ST	O	Strain (veterinary)
`PID-38`	Production Class	CE	O	Production class (veterinary)
`PID-39`	Tribal Citizenship	CWE	O	Added in v2.6

PID-1 O

Set ID SI

Sequence number (usually 1)

PID-2 W

Patient ID (External) CX

Withdrawn in v2.3.1 — use PID-3

★ PID-3 R

Patient Identifier List CX

MRN and all identifiers (repeating)

Primary matching key. Must include assigning authority (CX.4) and identifier type (CX.5). Repeat for multiple identifiers (MRN, EMPI, account number).

PID-4 W

Alternate Patient ID CX

Withdrawn — use PID-3

★ PID-5 R

Patient Name XPN

Family^Given^Middle^Suffix^Prefix

XPN data type. Can repeat for legal name, alias, maiden name. XPN.7 indicates name type (L=Legal, A=Alias, M=Maiden).

PID-6 O

Mother's Maiden Name XPN

Used for identity verification

★ PID-7 O

Date/Time of Birth TS

YYYYMMDD format

Critical for patient matching. Some systems send YYYYMMDDHHMMSS — receiving systems should handle both formats.

★ PID-8 O

Administrative Sex IS

M, F, O, U, A, N

PID-9 W

Patient Alias XPN

Withdrawn in v2.4

PID-10 O

Race CE

HL7 table 0005

★ PID-11 O

Patient Address XAD

Street^City^State^Zip^Country

PID-12 W

County Code IS

Withdrawn — use PID-11

★ PID-13 O

Phone (Home) XTN

Home phone number

★ PID-14 O

Phone (Business) XTN

Work phone number

PID-15 O

Primary Language CE

Preferred language

PID-16 O

Marital Status CE

HL7 table 0002

PID-17 O

Religion CE

HL7 table 0006

★ PID-18 O

Patient Account Number CX

Visit/encounter account

Often used as a secondary matching key. Maps to the encounter/visit-level account in the receiving system.

PID-19 W

SSN (Patient) ST

Withdrawn — use PID-3

Still populated by many legacy systems. Modern implementations should use PID-3 with identifier type SS.

PID-20 W

Driver's License DLN

Withdrawn in v2.5

PID-21 O

Mother's Identifier CX

Links newborn to mother

PID-22 O

Ethnic Group CE

HL7 table 0189

PID-23 O

Birth Place ST

City/state of birth

PID-24 O

Multiple Birth Indicator ID

Y/N for twins, triplets

PID-25 O

Birth Order NM

1, 2, 3 for multiples

PID-26 O

Citizenship CE

Country of citizenship

PID-27 O

Veterans Status CE

Military veteran indicator

PID-28 W

Nationality CE

Withdrawn in v2.4

PID-29 O

Patient Death Date TS

Date and time of death

PID-30 O

Patient Death Indicator ID

Y/N

PID-31 O

Identity Unknown ID

Y if patient cannot be identified

PID-32 O

Identity Reliability IS

AL (alias name), UA (unknown/default address), US (unknown/default SSN), UD (unknown/default DOB)

PID-33 O

Last Update Date TS

When PID data was last modified

PID-34 O

Last Update Facility HD

Facility that last updated the record

PID-35 O

Taxonomic Classification CE

Species code (veterinary)

PID-36 O

Breed Code CE

Breed (veterinary)

PID-37 O

Strain ST

Strain (veterinary)

PID-38 O

Production Class CE

Production class (veterinary)

PID-39 O

Tribal Citizenship CWE

Added in v2.6

R = Required, O = Optional, C = Conditional, W = Withdrawn (backward compatibility only)

PID-3: Patient Identifier List (Critical Field)

PID-3 is the most important field in the PID segment. It carries a repeating list of patient identifiers, each with its assigning authority and identifier type:

PID|||MRN12345^^^MAIN_HOSP^MR~SSN987654321^^^SSA^SS~ENT00567^^^MAIN_HOSP^AN||...

PID-3 Components

Component	Name	Example
CX.1	ID Number	MRN12345
CX.2	Check Digit	(optional)
CX.3	Check Digit Scheme	(optional)
CX.4	Assigning Authority	MAIN_HOSP
CX.5	Identifier Type	MR (Medical Record Number)
CX.6	Assigning Facility	(optional)

Common Identifier Types (CX.5)

Code	Meaning
MR	Medical Record Number
AN	Account Number
SS	Social Security Number
PI	Patient Internal Identifier
PT	Patient External Identifier
DL	Driver’s License
MA	Medicaid Number
MC	Medicare Number
NPI	National Provider Identifier
VN	Visit Number

Assigning Authority

The assigning authority (CX.4) identifies which system or facility assigned the identifier. In a multi-facility health system, a patient may have different MRNs at each facility:

MRN12345^^^HOSP_A^MR~MRN67890^^^HOSP_B^MR~EMPI99999^^^ENTERPRISE^PI

The receiving system must know which assigning authority’s MRN to use for patient matching in its own database.

PID-5: Patient Name

The XPN (Extended Person Name) data type structures the patient’s name:

DOE^JOHN^ALEXANDER^III^DR^PHD

Component	Name	Example
XPN.1	Family Name	DOE
XPN.2	Given Name	JOHN
XPN.3	Middle Name	ALEXANDER
XPN.4	Suffix	III
XPN.5	Prefix	DR
XPN.6	Degree	PHD
XPN.7	Name Type	L (Legal), A (Alias), M (Maiden)

PID-5 can repeat — for example, legal name followed by alias:

DOE^JOHN^A^^^||~DOE^JACK^^^^A||

PID-8: Administrative Sex Codes

Code	Meaning
M	Male
F	Female
O	Other
U	Unknown
A	Ambiguous
N	Not applicable

Key Implementation Considerations

Patient Matching Pitfalls

The most common PID-related integration errors:

Wrong assigning authority: Mapping the wrong MRN when multiple facilities share an interface
Missing identifier type: Not populating CX.5, leaving receiving systems unable to classify the identifier
Name format mismatches: Sending “JOHN A” in the given name field vs separate given and middle components
Date format inconsistency: Some systems send DOB as YYYYMMDD, others as YYYYMMDDHHMMSS
SSN in PID-19 vs PID-3: Withdrawn field PID-19 is still populated by many legacy systems; modern implementations should use PID-3 with identifier type SS

Multi-Facility MRN Handling

In health systems with multiple facilities, each facility may assign its own MRN. The enterprise master patient index (EMPI) assigns a global identifier that links facility-specific MRNs together. PID-3 should contain both:

The facility-specific MRN (for local system matching)
The EMPI identifier (for cross-facility correlation)

Demographic Updates (ADT^A08 / A31)

When patient demographics change, the source system sends an ADT message with the updated PID segment. Receiving systems must:

Match on PID-3 identifiers to find the existing patient record
Update only the fields that changed (some systems send the full PID regardless)
Maintain audit history of demographic changes
Handle name changes carefully (marriage, legal name change) without creating duplicate records

HL7 ADT Messages ADT event types and message structure — the primary carrier of PID segment data.

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

HL7 Resource Center Message types, segments, reference guides, and integration tools.

HL7 v2 Message Types The HL7 v2 messages this segment appears in — ADT, ORU, ORM, and more.

HL7 v2 Segment Reference Browse field-by-field references for every HL7 v2 segment.

HL7 v2 Data Types The composite data types — CX, XPN, CE, and others — that segment fields are built from.