ICD-10-CM vs ICD-10-PCS: Key Differences for Medical Coders
- Jan 31, 2025
If you're new to medical coding or transitioning between healthcare settings, understanding the difference between ICD-10-CM and ICD-10-PCS is essential. While both are part of the ICD-10 coding system, they serve different purposes and are used in different contexts.
Quick Answer: What's the Difference?
| Feature | ICD-10-CM | ICD-10-PCS |
|---|---|---|
| Full Name | Clinical Modification | Procedure Coding System |
| Purpose | Diagnosis codes | Procedure codes |
| Used By | All healthcare providers | Inpatient hospitals only |
| Code Length | 3-7 characters | Always 7 characters |
| Total Codes | ~72,000 | ~78,000 |
| Code Format | Alphanumeric with decimal | Alphanumeric, no decimal |
| Example | E11.65 | 0HR0X7Z |
Bottom line: ICD-10-CM describes what's wrong with the patient (diagnoses). ICD-10-PCS describes what was done to the patient (procedures) in inpatient settings.
ICD-10-CM: Diagnosis Codes
ICD-10-CM (International Classification of Diseases, 10th Revision, Clinical Modification) is used to code patient diagnoses across all healthcare settings.
Who Uses ICD-10-CM?
- Hospitals (inpatient and outpatient)
- Physician offices
- Urgent care centers
- Emergency departments
- Ambulatory surgery centers
- Home health agencies
- Skilled nursing facilities
- All healthcare providers submitting claims
Code Structure
ICD-10-CM codes are 3 to 7 characters:
``
E11.65
│││ └─ Specificity (hyperglycemia)
││└─── Decimal point
│└──── Category (Type 2 diabetes)
└───── Chapter (Endocrine)
Format rules:
- First character: Letter (A-Z)
- Characters 2-3: Numbers
- Decimal after position 3 (if more than 3 characters)
- Characters 4-7: Alphanumeric for additional detail
Common Examples
| Code | Description |
|---|---|
| I10 | Essential hypertension |
| E11.9 | Type 2 diabetes without complications |
| J06.9 | Acute upper respiratory infection |
| M54.5 | Low back pain |
| Z23 | Encounter for immunization |
ICD-10-PCS: Procedure Codes
ICD-10-PCS (International Classification of Diseases, 10th Revision, Procedure Coding System) is used exclusively for coding inpatient hospital procedures.
Who Uses ICD-10-PCS?
ONLY inpatient hospitals. This is a critical distinction:
| Setting | Diagnosis Codes | Procedure Codes |
|---|---|---|
| Inpatient hospital | ICD-10-CM | ICD-10-PCS |
| Outpatient hospital | ICD-10-CM | CPT/HCPCS |
| Physician office | ICD-10-CM | CPT/HCPCS |
| Ambulatory surgery | ICD-10-CM | CPT/HCPCS |
If you work outside of inpatient hospital coding, you likely won't use ICD-10-PCS.
Code Structure
ICD-10-PCS codes are always exactly 7 characters with no decimal:
``
0HR0X7Z
│││││││
│││││└┴─ Qualifier (Z = no qualifier)
││││└─── Device (7 = autologous tissue)
│││└──── Approach (X = external)
││└───── Body Part (0 = scalp)
│└────── Root Operation (R = replacement)
└──────── Section (0 = Medical & Surgical)
Each position has a specific meaning, and codes are built character by character.
PCS Sections
| Section | Code | Examples |
|---|---|---|
| Medical and Surgical | 0 | Bypass, excision, repair |
| Obstetrics | 1 | Delivery, cesarean section |
| Placement | 2 | Immobilization, packing |
| Administration | 3 | Infusion, transfusion |
| Measurement & Monitoring | 4 | EKG, cardiac output |
| Extracorporeal Assistance | 5 | Ventilation, pacing |
| Extracorporeal Therapies | 6 | Dialysis, phototherapy |
| Osteopathic | 7 | OMT procedures |
| Other Procedures | 8 | Acupuncture, yoga therapy |
| Chiropractic | 9 | Chiropractic manipulation |
| Imaging | B | X-ray, CT, MRI |
| Nuclear Medicine | C | PET scan, nuclear imaging |
| Radiation Therapy | D | Radiation oncology |
| Physical Rehabilitation | F | PT, OT, speech therapy |
| Mental Health | G | Psychological testing |
| Substance Abuse | H | Detoxification, counseling |
| New Technology | X | Emerging procedures |
Browse All ICD-10-PCS Sections →
Side-by-Side Comparison
Code Format Example
Same patient, same encounter:
| System | Code | Meaning |
|---|---|---|
| ICD-10-CM | K80.10 | Calculus of gallbladder with chronic cholecystitis |
| ICD-10-PCS | 0FT44ZZ | Resection of gallbladder, percutaneous endoscopic |
The CM code describes the diagnosis (gallstones with inflammation), while the PCS code describes the procedure performed (laparoscopic removal of gallbladder).
Code Structure Comparison
| Aspect | ICD-10-CM | ICD-10-PCS |
|---|---|---|
| Length | 3-7 characters | Always 7 characters |
| First character | Letter | Alphanumeric |
| Decimal point | After position 3 | None |
| Placeholder | X (when needed) | Not used |
| Building codes | Look up complete code | Build character by character |
Update Cycles
Both systems are updated annually by CMS, effective October 1st:
- ICD-10-CM: ~400 new codes, ~30 revised, ~20 deleted each year
- ICD-10-PCS: ~200 new codes annually (often in New Technology section)
When to Use Each System
Use ICD-10-CM When:
- Reporting any diagnosis in any healthcare setting
- Documenting the patient's condition(s)
- Coding for physician services
- Coding for outpatient services
- Supporting medical necessity for services
Use ICD-10-PCS When:
- Coding procedures performed during an inpatient hospital stay
- The patient is admitted to an acute care hospital
- Creating the inpatient claim (UB-04)
Don't Confuse With:
- CPT codes - Physician and outpatient procedure codes (maintained by AMA)
- HCPCS codes - Medicare procedure codes for supplies, equipment, services
- DRG codes - Payment categories derived from ICD-10 codes
How They Work Together
In an inpatient hospital encounter, both systems are used on the same claim:
Example: Inpatient Cholecystectomy
Diagnosis codes (ICD-10-CM):
- K80.10 - Calculus of gallbladder with chronic cholecystitis (principal diagnosis)
- I10 - Essential hypertension (secondary diagnosis)
- E11.9 - Type 2 diabetes without complications (secondary diagnosis)
Procedure code (ICD-10-PCS):
- 0FT44ZZ - Resection of gallbladder, percutaneous endoscopic approach
The combination of these codes determines the MS-DRG (Medicare payment category) for reimbursement.
Learning Each System
For ICD-10-CM:
- Understand the 21 chapter organization
- Learn to navigate from category to specific code
- Master Excludes1 vs Excludes2 notes
- Practice with common diagnoses in your specialty
Resources:
- Browse ICD-10-CM hierarchy
- Search ICD-10-CM codes
- Common codes by specialty
For ICD-10-PCS:
- Learn the 7-character structure
- Understand root operations (excision vs resection, etc.)
- Practice building codes character by character
- Use PCS tables for accurate code construction
Resources:
- Browse ICD-10-PCS sections
- Interactive PCS code builder
Frequently Asked Questions
Do I need to learn both systems?
It depends on your work setting:
- Inpatient hospital coders: Yes, both systems
- All other settings: ICD-10-CM only (use CPT/HCPCS for procedures)
Which is harder to learn?
Most coders find ICD-10-PCS more challenging initially because:
- Codes are built character by character
- You must understand root operation definitions
- Tables require careful navigation
ICD-10-CM is more intuitive since codes are looked up rather than constructed.
Can I use ICD-10-PCS for outpatient surgery?
No. Outpatient surgical procedures use CPT codes, even in hospital outpatient departments. ICD-10-PCS is exclusively for inpatient procedures.
Are the codes related?
Not directly. While both cover medical conditions/procedures, they were developed independently:
- ICD-10-CM was adapted from WHO's ICD-10
- ICD-10-PCS was developed from scratch by CMS specifically for US inpatient coding
Where can I find official code sets?
Both are available free from CMS.gov:
- ICD-10-CM files
- ICD-10-PCS files
Start Exploring
- Browse ICD-10-CM - All diagnosis codes
- Browse ICD-10-PCS - All procedure codes
- Search ICD-10 - Quick keyword lookup
- AI Analyzer - Extract codes from clinical notes
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Data sourced from CMS.gov. Updated for 2026 code sets (effective October 1, 2025).