Laterality in ICD-10-CM specifies which side of the body is affected by a condition. According to the official ICD-10 coding guidelines, many codes for paired organs and structures include laterality designations that must be assigned when the information is available in the medical record.
Understanding Laterality
ICD-10-CM includes laterality for conditions affecting paired body parts such as:
- Eyes and ears
- Arms and legs (upper and lower extremities)
- Lungs and kidneys
- Breasts and ovaries
- Joints (knees, hips, shoulders, etc.)
Laterality Options
Right
Use when the condition affects the right side only. Most codes end in "1" for right side (e.g., H40.11x1 - Primary open-angle glaucoma, right eye).
Left
Use when the condition affects the left side only. Most codes end in "2" for left side (e.g., H40.11x2 - Primary open-angle glaucoma, left eye).
Bilateral
Use when the same condition affects both sides. Most codes end in "3" for bilateral (e.g., H40.11x3 - Primary open-angle glaucoma, bilateral).
Unspecified
Use ONLY when the documentation does not specify which side is affected. Most codes end in "9" for unspecified.
Important
Unspecified laterality codes should only be used when the medical record does not document which side is affected. Using unspecified when laterality is documented may result in audit findings.
When is Laterality Required?
Laterality is required when:
- The ICD-10 code structure includes laterality options
- The medical documentation specifies the affected side
- The condition affects a paired organ or structure
Validate Against ICD 10 CM Coding Guidelines
Our Code Auditor flags missing laterality designations based on official FY2026 guidelines.
Look up ICD 10 CM codes to find diagnosis codes before validation.
Coding Bilateral Conditions
When a bilateral condition exists, there are two options:
- Use bilateral code: If a bilateral code exists, use it (preferred)
- Use two codes: If no bilateral code exists, code each side separately
Best Practices
- Always review documentation for laterality information
- Query providers when laterality is not documented but needed
- Never assume laterality - it must be documented
- Use validation tools to catch missing laterality
Missing laterality is among the most common ICD-10 coding errors that lead to claim denials and rework. Proper laterality documentation supports both compliance and accurate reimbursement.