Coding accuracy depends heavily on specialty-specific knowledge — the same visit can be coded very differently in cardiology versus dermatology versus behavioral health. This guide summarizes the coding landmarks for the specialties that generate the most billing questions. Each section covers the CPT/HCPCS ranges you’ll use most and specialty-specific pitfalls.
Cardiology
Primary code range: 70000–79999 (diagnostic imaging) and 92920–93799 (cardiovascular procedures)
Cardiology coding combines E/M visits with high-value procedures like cardiac catheterizations, echocardiograms, and stress tests. Watch for bundling edits between diagnostic tests performed on the same day, and use modifier 26 (professional component) / TC (technical component) correctly when a physician only interprets a test performed elsewhere.
Orthopedics
Primary code range: 20000–29999 (musculoskeletal system)
Orthopedic coding is procedure-heavy: fracture care, joint injections, and surgical scopes. Global surgical packages are a major pitfall — many post-op visits are already bundled into the surgery’s global period and shouldn’t be billed separately. Modifiers 58, 78, and 79 govern related procedures during that window.
Mental & Behavioral Health
Primary code range: 90785–90899 (psychiatry) and 96130–96139 (psych/neuropsych testing)
Time-based codes are central here — many psychotherapy codes (e.g., 90832, 90834, 90837) are chosen by session length, so accurate time documentation is essential. Add-on code 90785 for interactive complexity and correct use of telehealth modifiers (95, GT) are common problem areas.
Dermatology
Primary code range: 10000–19999 (integumentary system)
Dermatology mixes E/M visits, biopsies, and destruction/excision procedures, often on the same visit. Correct use of modifier 25 (significant, separately identifiable E/M) is one of the most frequently audited issues in this specialty.
Radiology
Primary code range: 70000–79999
Radiology billing separates the professional component (physician interpretation) from the technical component (equipment/staff), using modifiers 26 and TC. Bundling rules between related imaging studies are common denial triggers.
Anesthesia
Primary code range: 00100–01999, billed with time units rather than flat fees
Anesthesia uses a unique payment formula: base units (by procedure) plus time units, adjusted by modifiers like AA, QK, or QX depending on who administered the anesthesia and how it was medically directed.
OB/GYN
Primary code range: 58300–59899 (female genital system, maternity care)
Global maternity billing bundles routine antepartum care, delivery, and postpartum care into a single code — billing pieces separately outside that bundle is a common and costly mistake.
Physical & Occupational Therapy
Primary code range: 97110–97799
Therapy billing is time-based using 15-minute units under the “8-minute rule,” and often requires functional limitation reporting and therapy caps tracking depending on payer.
Emergency Medicine
Primary code range: 99281–99285 (ED E/M levels)
ED visit levels are chosen by medical decision-making complexity and are frequently audited; documentation must clearly support the level billed. Critical care time (99291/99292) has its own strict time-tracking requirements.
Family & Internal Medicine
Primary code range: 99202–99215 (office/outpatient E/M)
The 2021 E/M guideline overhaul shifted level selection to medical decision-making or total time — accurate, specific documentation of both is what supports the code chosen.
New to coding? Start with our Medical Billing Process overview, then explore official code sets and lookup tools on our Free Resources page.