ICD-10-CM Official Guidelines FY 2025

ICD-10-CM Official Guidelines for Coding and Reporting — FY 2025

Approved by the Cooperating Parties: AHA, AHIMA, CMS, NCHS

Authority & Scope

These guidelines are official under HIPAA and must be followed for all healthcare settings when assigning ICD-10-CM diagnosis codes. They complement—but do not override—the conventions and instructions in the ICD-10-CM Tabular List and Alphabetic Index. 12

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📚 Document Structure

Section I: Conventions, General Guidelines & Chapter-Specific Guidelines
├── A. Conventions for ICD-10-CM
│   ├── Alphabetic Index vs. Tabular List usage
│   ├── Format, placeholders, 7th characters
│   ├── Abbreviations (NEC, NOS), punctuation, Excludes notes
│   └── Etiology/manifestation conventions
├── B. General Coding Guidelines  
│   ├── Code selection, specificity, signs/symptoms
│   ├── Acute/chronic, combination codes, sequela
│   ├── Laterality, documentation standards, clinical criteria
│   └── Chapter-specific rules (HIV, neoplasms, diabetes, etc.)
└── C. Chapter-Specific Guidelines (Chapters 1-22)
    ├── Infectious diseases, neoplasms, endocrine, circulatory...
    ├── Injury poisoning, external causes, Z codes
    └── Special topics: sepsis, malnutrition, opioid use, etc.

Section II: Selection of Principal Diagnosis (Inpatient)
Section III: Reporting Additional Diagnoses (Inpatient)  
Section IV: Outpatient Coding & Reporting Guidelines
Appendix I: Present on Admission (POA) Reporting Guidelines

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🔑 Section I.A: Core Conventions (Must-Know)

1. Alphabetic Index → Tabular List Workflow

✅ ALWAYS:
1. Locate term in Alphabetic Index
2. Verify code in Tabular List
3. Confirm full character count (3-7 characters + 7th if required)
4. Check for instructional notes (Includes, Excludes, Code first, Use additional)
 
❌ NEVER:
- Code directly from Alphabetic Index without Tabular verification
- Assign incomplete codes (missing required characters)

2. Excludes Notes: Critical Distinction

Type	Meaning	Can Codes Be Used Together?
Excludes1	”NOT CODED HERE!” - Mutually exclusive conditions	❌ No (unless unrelated per provider documentation)
Excludes2	”Not included here” - Condition is separate but may coexist	✅ Yes, if both documented

Excludes1 Application

F45.8 (Other somatoform disorders) Excludes1: G47.63 (Sleep related teeth grinding)
→ Do NOT report both for teeth grinding alone.
→ MAY report both if patient has psychogenic dysmenorrhea (F45.8) AND sleep bruxism (G47.63) as unrelated conditions.

3. “With” / “In” Presumption Rule

When "with" or "in" appears in:
• Code title
• Alphabetic Index entry  
• Tabular List instructional note
 
→ Classification PRESUMES causal relationship.
→ Code as related EVEN WITHOUT provider documentation linking them.
 
EXCEPTIONS:
• Documentation explicitly states conditions are unrelated
• Specific guideline requires documented linkage (e.g., sepsis + organ dysfunction)

Query Trigger

If documentation is ambiguous about relationship between conditions linked by “with” in the classification, query for clarification—but default to coding as related if no conflict exists.

4. Placeholder “X” and 7th Characters

// Example: Poisoning by aspirin, accidental, initial encounter
T39.011A → Requires 7th character "A" for initial encounter
 
// If code has fewer than 6 characters before 7th char:
T36.0X5A → "X" fills 5th character position to allow 7th char in 7th position

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⚙️ Section I.B: General Coding Guidelines (High-Yield)

Specificity Hierarchy

1. Code to HIGHEST number of characters available (3-7)
2. Code to HIGHEST level of specificity DOCUMENTED
3. Use "unspecified" ONLY when documentation lacks detail for more specific code
 
✅ Documented: "Type 2 diabetes with mild nonproliferative retinopathy, right eye"  
→ E11.3211 (7 characters)
 
❌ Documented: "Diabetes with eye problems"  
→ E11.9 + H53.9 (unspecified) — then QUERY for specificity

Signs/Symptoms vs. Definitive Diagnosis

Scenario	Coding Approach
Definitive diagnosis established	Code the diagnosis; do NOT code associated routine signs/symptoms
No definitive diagnosis after study	Code sign/symptom as principal/first-listed
Sign/symptom NOT routinely associated with dx	Code both if clinically significant

Acute + Chronic Same Condition

IF Alphabetic Index has separate subentries at same indentation level for:
• Acute [condition]  
• Chronic [condition]
 
→ CODE BOTH, sequence ACUTE first.
 
Example:  
Alphabetic Index under "Bronchitis":  
• acute  
• chronic  
• acute and chronic  
 
Documentation: "Acute exacerbation of chronic bronchitis"  
→ J44.1 (COPD with acute exacerbation) — combination code captures both

Sequela (Late Effects) Coding Rule

General Rule:  
1. Code for NATURE/CONDITION of sequela FIRST  
2. Code for SEQUELA (late effect) SECOND  
 
Exception:  
If sequela code INCLUDES manifestation in its title or expanded characters,  
→ Use ONLY the sequela code.
 
NEVER code acute phase injury/illness with sequela code.
 
Example:  
Old cerebral infarction with residual aphasia  
→ I69.321 (Aphasia following cerebral infarction) — single code captures both

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🎯 Section I.C: Chapter-Specific Highlights (Specialty Focus)

Chapter 1: Infectious Diseases (A00-B99) — Sepsis Guidelines 12

SEPSIS CODING SEQUENCE:
1. Code underlying systemic infection FIRST (e.g., A41.9 Sepsis)
2. Code severe sepsis IF documented: R65.20 or R65.21
3. Code associated acute organ dysfunction(s) SECONDARY
 
❗ Critical:  
• "Urosepsis" is non-specific — query for sepsis vs. UTI  
• "Sepsis syndrome" = code as sepsis (A41.9) unless provider specifies otherwise  
• Organ dysfunction must be DOCUMENTED (not inferred) to code separately

Chapter 2: Neoplasms (C00-D49) — Key Rules

PRIMARY vs. SECONDARY MALIGNANCY:
• Admission for treatment of primary site → Code primary malignancy as principal dx
• Admission for treatment of metastasis → Code secondary malignancy as principal dx  
• Both treated → Sequence based on reason for admission
 
CHEMOTHERAPY/IMMUNOTHERAPY/RADIATION:
• Z51.0 (Encounter for antineoplastic radiation) or Z51.11/Z51.12 (chemo) as principal dx  
• Malignancy code as secondary (unless complication of therapy is reason for admission)
 
HISTORY OF MALIGNANCY:
• Use Z85.- codes ONLY when primary treatment completed AND no current evidence of disease  
• Do NOT use Z85.- if patient is still receiving treatment or has active disease

Chapter 4: Endocrine (E00-E89) — Diabetes Mellitus

DIABETES CODING HIERARCHY:
1. Type (E10.- Type 1, E11.- Type 2, etc.)  
2. Complication category (e.g., .3- for ophthalmic, .4- for neurological)  
3. Specific manifestation (e.g., .311 = with mild NPDR, right eye)  
4. Control status (if documented: uncontrolled, in remission, etc.)
 
✅ Documented: "Type 2 diabetes with chronic kidney disease stage 4"  
→ E11.22 (Type 2 DM with diabetic CKD) + N18.4 (CKD stage 4)
 
❗ Query if:  
• Type not specified AND no clues in record (default to E11.- per guidelines)  
• "Diabetic" used without specifying type or complication

Chapter 9: Circulatory (I00-I99) — Hypertension & Heart Disease

HYPERTENSION WITH HEART/KIDNEY DISEASE:
• "Hypertensive heart disease" → I11.- (code also heart failure if present: I50.-)  
• "Hypertensive CKD" → I12.- (code also N18.- stage)  
• "Hypertensive heart AND CKD" → I13.- (code also I50.- and N18.- as needed)
 
❗ Do NOT assume relationship:  
If documentation says "hypertension and heart failure" without linking,  
→ Code I10 (Essential hypertension) + I50.9 (Heart failure) separately  
→ Query if clinical picture suggests causal relationship

Chapter 19: Injury/Poisoning (S00-T88) — 7th Character Rules

7TH CHARACTER REQUIREMENTS (Chapter 19):
A = Initial encounter (active treatment)  
D = Subsequent encounter (routine healing)  
S = Sequela (late effects)
 
FRACTURE CODING:
• Must specify: open/closed, displaced/nondisplaced, laterality, encounter type  
• Pathologic fracture: M84.4- (code also underlying cause, e.g., C79.51 for metastasis)
 
ADVERSE EFFECT vs. POISONING:
• Adverse effect: Drug correctly prescribed/administered → T36-T50 + 5th/6th char "5"  
• Poisoning: Wrong drug/dose/intent → T36-T50 + 5th/6th char "1-4" + intent code (X40-X44, etc.)

Chapter 21: Z Codes (Z00-Z99) — When to Use

Z CODES AS PRINCIPAL/FIRST-LISTED:
✅ Z00-Z13: Examinations (when no complaint/diagnosis)  
✅ Z20-Z29: Potential health hazards (e.g., Z20.828 Contact with COVID-19)  
✅ Z30-Z39: Reproductive services  
✅ Z40-Z53: Aftercare/follow-up (when treatment completed)  
✅ Z55-Z65: Social determinants impacting care  
✅ Z71-Z76: Other health service encounters  
✅ Z85-Z87: Personal history (when no current disease)
 
❌ Z codes NOT for principal dx when:  
• Current illness/injury is reason for encounter  
• Z code describes circumstance only (use as secondary)
 
EXAMPLE:  
Patient admitted for chemotherapy for breast cancer  
→ Z51.11 (Encounter for antineoplastic chemotherapy) = principal  
→ C50.911 (Malignant neoplasm of right breast) = secondary

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🏥 Sections II-III: Inpatient Diagnosis Selection

Principal Diagnosis Definition (Section II)

“That condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care.” 12

Key Application Rules

Scenario	Principal Dx Guidance
Symptom → Confirmed diagnosis during stay	Code confirmed diagnosis
Two equally valid dx	Sequence based on circumstances of admission
Uncertain diagnosis at discharge	Code as if condition exists (inpatient only)
Complication of care	Code complication as principal IF it is reason for admission
Observation → Admission	Code reason for observation as principal if it becomes reason for admission

Additional Diagnoses Criteria (Section III)

Code ALL conditions that:

✅ Require clinical evaluation  
✅ Require therapeutic treatment  
✅ Require diagnostic procedures  
✅ Extend length of stay  
✅ Increase nursing care/monitoring  
 
❌ Do NOT code:  
• Historical conditions with no current impact  
• Abnormal findings without clinical significance  
• Conditions ruled out after study (use Z03.- for observation only)

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🚑 Section IV: Outpatient Guidelines (Key Differences)

Uncertain Diagnosis Rule

OUTPATIENT:  
❌ NEVER code "probable," "suspected," "rule out" as confirmed  
✅ Code signs/symptoms or reason for encounter instead  
 
INPATIENT:  
✅ Code uncertain diagnoses as if confirmed (per Section II.H)

First-Listed Diagnosis Selection

For outpatient encounters:  
1. Reason for encounter (chief complaint)  
2. If multiple reasons: sequence based on resources used/provider focus  
3. For routine prenatal visits: Z34.- as first-listed  
4. For post-op follow-up: Z48.- + procedure code + any complications

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📋 Appendix I: POA Reporting Guidelines

POA Indicator Assignment Logic

Condition Status	POA Value	Notes
Clearly present at admission	Y	Most common
Clearly developed after admission	N	May trigger HAC payment adjustment
Documentation insufficient	U	Treated as “N” for payment
Clinically undeterminable	W	Query provider
Exempt code (e.g., external cause)	1	Per CMS exempt list

HAC (Hospital-Acquired Condition) Impact

If POA = "N" AND code is on CMS HAC list:  
→ Medicare will NOT pay higher DRG weight for that CC/MCC  
→ Hospital absorbs cost of complication  
 
Common HACs affecting CC/MCC:  
• Stage 3/4 pressure ulcers (L89.2-, L89.3-)  
• Catheter-associated UTI (T83.51-)  
• Postoperative PE/DVT (I26.99, I82.81-)  
• Falls/trauma in facility (W00-W19 + injury code)

POA Best Practice

Document “present on admission” status explicitly in H&P or progress notes when clinically relevant. Reduces query burden and supports accurate POA assignment.

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🔍 Clinical Validation & Query Essentials

When to Query (Per Guidelines)

✅ Documentation conflicts (e.g., progress note vs. discharge summary)  
✅ Diagnosis stated without supporting clinical criteria  
✅ Severity not specified when CC/MCC depends on it  
✅ Relationship between conditions unclear when classification presumes linkage  
✅ "Rule out" diagnosis in inpatient record at discharge  
 
❌ Do NOT query for:  
• Coder preference when documentation is clear  
• Clinical judgment calls within provider discretion  
• Adding diagnoses not documented anywhere in record

Query Template Structure

Subject: Clinical Validation Query — [Patient MRN] — [Condition]
 
Clinical Indicators in Record:  
• [List relevant labs, imaging, assessments]  
• [Quote provider documentation]
 
Coding Guidance:  
• Per ICD-10-CM Official Guidelines Section I.B.19, code assignment is based on provider diagnostic statement.  
• For [condition] to be reported, documentation must support [specific criteria per guideline].
 
Request:  
Please clarify:  
☐ Is [condition] confirmed?  
☐ If yes, is it [acute/chronic/severe/etc.]?  
☐ Is it present on admission or developed during stay?  
☐ Is it related to [other documented condition]?
 
Provider Response: _________________________  
Signature/Date: _________________________

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🔗 Related Vault Notes

• CMS MS-DRG Definitions Manual v42.0
• CC-MCC Reference List FY2025
• Clinical Validation Query Templates
• POA Reporting Quick Reference
• Chapter-Specific Coding Cheat Sheets

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📚 Official Resources

• FY 2025 ICD-10-CM Guidelines (PDF) 12
• ICD-10-CM Code Tables FY 2025
• Cooperating Parties Website
• AHA Coding Clinic for ICD-10-CM/PCS — Official coding advice

Bottom Line

The ICD-10-CM Official Guidelines are the rulebook for diagnosis coding. Mastery requires: (1) understanding conventions (Excludes, “with”, placeholders), (2) applying chapter-specific rules (sepsis, diabetes, trauma), (3) distinguishing inpatient vs. outpatient rules (uncertain dx, principal selection), and (4) integrating POA/HAC logic. Always pair guideline knowledge with clinical documentation review—and query when in doubt.

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Last synced: $(date)
Next update: FY 2026 Guidelines (expected July 2025)