OHIP Diagnostic Code Lookup
Search Ontario’s complete diagnostic code database instantly. Updated March 2026 (INFOBulletin 260314) — 2 new codes, 41 updated descriptions. Free — no signup required.
Regulatory Currency
This guide reflects the following MOH INFOBulletins:
- 260314 — Diagnostic Code Update (March 2026) (Mar 13, 2026)
Last verified: April 16, 2026
What’s New in March 2026
The MOH modernized diagnostic code descriptions effective March 13, 2026 (INFOBulletin 260314):
• 2 new codes: 308 (Gender Dysphoria) and 489 (Respiratory Syncytial Virus)
• 2 deleted codes: 100 and 903 (outdated terminology)
• 41 codes received updated descriptions
What Are OHIP Diagnostic Codes?
OHIP diagnostic codes are 3-digit ICD-8-based codes required on most OHIP claims. Ontario uses 646 diagnostic codes to classify the reason for each patient encounter. Correct diagnostic coding directly affects FHO+ acuity modifier payments — CIHI’s Population Grouper uses these codes to assign patients to acuity bands 1–5, which determines your capitation adjustment.
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Free Billing AssessmentHow Diagnostic Codes Affect Your FHO/FHO+ Payments
What are patient acuity bands?
CIHI’s Population Grouper assigns each of your rostered patients to an acuity band (1–5) based on the complexity of their diagnostic history. Band 5 represents the most complex patients. Your acuity modifier — which adjusts your capitation payments — is calculated from the distribution of bands across your roster.
Why precise codes matter for FHO+
Generic codes like 799 (“Other ill-defined conditions”) contribute less to a patient’s acuity classification than a specific code like 250 (Diabetes Mellitus) or 428 (Heart Failure). When a patient’s chronic conditions are not captured with the right codes, CIHI may assign them a lower acuity band than their actual complexity warrants.
Acute vs. chronic lookback windows
CIHI uses different lookback periods depending on condition type: chronic conditions use a 5-year lookback window, while acute conditions use a 2-year window. This means a chronic condition billed just once in the past 5 years can still contribute to a patient’s acuity band. Use the Acuity column in this tool to see how each code is classified.
Cross-provider contribution
Any OHIP-billing provider — specialists, ERs, urgent care — can contribute to your patient’s diagnostic history. A cardiologist billing 428 (Heart Failure) adds to your patient’s acuity profile, even though you are the FHO+ most-responsible physician. This is why CIHI acuity band assignment reflects the full care team’s diagnostic coding.
Looking for fee codes? → OHIP Fee Code Lookup | Claim rejected? → OHIP Rejection Code Lookup | Billing FHO+ codes? → FHO+ Billing Guide
Frequently Asked Questions
What are OHIP diagnostic codes?
OHIP diagnostic codes are 3-digit numeric codes required on most OHIP physician billing claims. They are based on the World Health Organization's International Classification of Diseases, 8th Revision (ICD-8). Physicians must include a diagnostic code on each claim to indicate the reason for the visit.
How many OHIP diagnostic codes are there?
The March 2026 OHIP diagnostic code set contains 646 total codes: 565 main ICD-8 codes across 18 clinical categories, plus 81 supplementary physiotherapy codes. Codes span infectious diseases (002\u2013136) through accidents and injuries (800\u2013999).
What changed in the March 2026 diagnostic code update?
The Ministry of Health issued INFOBulletin 260314, effective March 13, 2026. Changes include 2 new codes (308 \u2014 Gender Dysphoria, 489 \u2014 Respiratory Syncytial Virus), 2 deleted codes (100 and 903, both outdated terminology), and 41 codes with updated descriptions.
How do diagnostic codes affect FHO/FHO+ capitation payments?
For FHO/FHO+ physicians, CIHI assigns each rostered patient to an acuity band (1\u20135) based on their diagnostic history. The acuity band determines the acuity modifier applied to capitation payments. Using precise diagnostic codes \u2014 rather than vague catch-alls like code 799 \u2014 leads to more accurate acuity band assignment and appropriate payment levels.
Where do OHIP diagnostic codes come from?
OHIP diagnostic codes are based on the WHO ICD-8 classification, maintained and published by the Ontario Ministry of Health. The current version reflects the March 2026 update (INFOBulletin 260314). Published under the Ontario Open Government Licence.
What is diagnostic code 799?
Code 799 is "Other ill-defined conditions" \u2014 a catch-all used when a more specific diagnosis is not recorded. Physicians should avoid code 799 when a more specific code applies, as it provides less information about a patient's diagnostic history and can result in underestimated patient complexity during CIHI acuity band assignment.
Which OHIP fee codes require a diagnostic code?
Most OHIP assessment and procedure codes require a diagnostic code on the claim. This includes all A-prefix consultations and assessments, B-codes, C-codes, D-codes, F-codes, H-codes, K-codes, M-codes, N-codes, R-codes, S-codes, W-codes, and Z-codes. Codes that do not require a diagnostic code include laboratory claims (L-prefix), most premium add-on codes (E-prefix, except E077, E078, E102\u2013E359, E687, E985), capitation codes (Q-prefix, except Q601\u2013Q604 and Q619\u2013Q629 for specific group types), and ancillary codes (J-prefix, X-prefix). Use our OHIP Fee Code Lookup tool and look for the \u201cDx Required\u201d badge to confirm any specific code.
Data source: Ministry of Health, Ontario — Diagnostic Codes (March 2026) | INFOBulletin 260314
Published under the Ontario Open Government Licence. Last updated: April 2026.
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