Internal medicine billing is the process of coding and submitting claims for healthcare services provided by internists, who specialize in diagnosing and managing complex, chronic conditions in adults (such as hypertension, diabetes, and COPD).
This billing process requires:
- Correct CPT and ICD-10 coding to demonstrate medical necessity.
- Compliance with Medicare, Medicaid, and private insurer guidelines.
- Detailed documentation to support longer visit times and higher acuity care.
Unlike general primary care billing, internal medicine claims face unique challenges due to patient complexity, frequent chronic care management, and stricter reimbursement rules. Accurate coding and documentation directly impact claim approvals and practice revenue.
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Table of Contents
How Is Internal Medicine Billing Different from Primary Care Billing?
While both internal medicine and primary care providers deliver essential outpatient services, their billing practices reflect fundamentally different patient populations and clinical focuses.
Understanding these distinctions is critical for accurate coding, proper reimbursement, and compliance with payer requirements. Below, we break down the key differences in their billing patterns.
| Attribute | Internal Medicine Billing | Primary Care Billing |
|---|---|---|
| Patient Demographic | • Primarily adults (18+) • Some internists may see adolescents (14+) for transitional care | • Family medicine: All ages (newborns to seniors) • Pediatrics: Under 18 only |
| Common Visit Codes | 99214, 99215 (complex visits) 99490 (CCM), 99495 (TCM) G0439 (subsequent AWV) 99417 (prolonged services) | 99213 (established patient) 99381-99397 (preventive) G0438 (initial AWV) 90471 (vaccines) |
| Case Complexity | • High MDM for multiple chronic conditions • Frequent medication reconciliation | • Routine wellness visits • Acute episodic care • Preventive screenings |
| Medicare Billing | • Chronic Care Management (99490) • Transitional Care (99495-99496) • Remote Monitoring (99453-99457) | • Annual Wellness Visits (G0438/G0439) • Preventive services (G0101, G0121) • Vaccine administration |
| Billing Risks | • Undercoding complex visits • Missing CCM opportunities | • Overcoding routine visits • Incomplete preventive service documentation |
What Is the Billing Process for Internal Medicine?
The billing workflow follows a structured path from patient intake to claim resolution.
1. Eligibility Verification
- Verify insurance coverage in real-time using EDI or clearinghouse tools.
- Confirm prior authorization requirements (e.g., chronic care management, stress tests).
- Estimate patient financial responsibility (deductibles, copays, coinsurance).
Practices should also collect an assignment of benefits form to ensure insurers pay the provider directly and avoid collection delays.
2. Documentation in EHR
- Ensure SOAP notes reflect visit complexity and support the Medical Decision Making (MDM) level.
Choosing the right EHR billing system benefits internists by simplifying documentation.
- Document total time spent (including pre-visit review, face-to-face time, and post-visit coordination) when using time-based billing.
- Justify medical necessity for higher-level visits (e.g., 99214 requires moderate MDM or 30+ minutes).
3. Code Assignment (CPT & ICD-10)
- Assign accurate CPT codes (e.g., 99214 for established patients, 99490 for chronic care management).
Understanding medical billing and coding differences ensures proper role delegation and claim accuracy.
- Pair with specific ICD-10 codes (e.g., E11.65 for diabetes with hyperglycemia instead of E11.9).
- Apply modifiers when needed (e.g., -25 for separate E/M services, -33 for preventive care).
Understanding billing vs revenue cycle management ensures that internal medicine practices assign the right roles and avoid claim errors during CPT and ICD-10 code mapping.
4. Claim Submission
- Submit claims electronically using ANSI 837P or paper CMS-1500 forms.
Understanding how clearinghouses work clarifies data flow and error handling.
- Perform claim scrubbing to catch errors (e.g., missing modifiers, invalid codes).
Advanced claim scrubbing techniques reduce denials caused by coding mismatches.
- Follow payer-specific rules (e.g., Medicare vs. commercial insurance requirements).
5. Rejection and Denial Management
Address common denials:
- Unspecified ICD-10 codes (use more specific diagnoses).
- Modifier misuse (e.g., missing -25 for preventive + problem visits).
- Medical necessity disputes (appeal with supporting documentation).
Track timely filing deadlines (typically 90–180 days, depending on the payer).
Missing timely filing deadlines can void reimbursements even if documentation is perfect.
6. Payment Posting & Reporting
- Reconcile payments against contractual adjustments and expected reimbursements.
- Identify underpayments and follow up with payers.
- Analyze denial trends to improve future billing accuracy.
What Are the Most Common Internal Medicine CPT Codes?
Internists rely heavily on evaluation, chronic management, diagnostic testing, and preventive care codes.
| CPT Code | Description | Billing Insight |
|---|---|---|
| 99214 | Established patient, moderate MDM (30–39 min) | Time OR MDM-based—requires 2+ chronic conditions (e.g., HTN + DM) with medication review or test interpretation. |
| G0439 | Medicare Annual Wellness Visit (subsequent) | Must include health risk assessment (HRA), cognitive screening, and personalized prevention plan. |
| 99490 | Chronic Care Management (CCM) | 20+ mins/month of non-face-to-face care for 2+ chronic conditions; patient consent required. |
| 99358 | Prolonged non-face-to-face care | 30+ mins beyond usual service time (e.g., chart review, care coordination)—document start/stop times. |
| 94010 | Spirometry | Supports COPD (J44.9), asthma (J45.909), or restrictive lung disease; use -25 if billed with E/M. |
| 93000 | ECG with interpretation | Link to I10 (HTN), I48 (A-fib), R07.9 (chest pain), or I25.10 (CAD). |
| 93306 | Complete transthoracic echocardiogram | Document symptoms (e.g., dyspnea) or diagnoses (I50.9, I48, I35.0) for medical necessity. |
| 99396 | Preventive visit (age 40–64) | Includes comprehensive history, exam, and counseling; not billable with AWV (G0439). |
| 99397 | Preventive visit (age 65+) | Same as 99396 but for seniors; distinct from Medicare AWV (can bill separately if criteria met). |
Modifier Tip: Use -25 when billing a separate, significant E/M service (e.g., office visit for dizziness + ECG).
Which ICD-10 Codes Are Used in Internal Medicine Billing?
ICD-10 codes must reflect documented diagnoses and medical necessity. Always follow official ICD-10-CM guidelines and payer-specific rules.
| ICD-10 Code | Condition | Reimbursement & Documentation Notes |
|---|---|---|
| I10 | Essential Hypertension | Use I11.x (hypertensive heart disease) if cardiac involvement is documented. If unspecified is the only option supported, I10 is acceptable but may trigger audits. |
| E11.9 | Type 2 Diabetes without complication | Add Z79.4 if insulin-dependent. For complications (neuropathy, retinopathy), use specific codes (E11.4x, E11.3x). |
| J44.9 | COPD, unspecified | If details are lacking, J44.9 is permitted, but add Z87.891 (smoking history) or F17.2xx + Z72.0 (active smoker) if relevant. |
| N18.3 | CKD Stage 3 | Track progression (N18.4, N18.5). Always code comorbidities (e.g., I12.9 for hypertensive CKD). |
| F32.9 | Major Depressive Disorder, unspecified | Use severity-specific codes (F32.1, F32.2) if documented. If not, F32.9 is clinically valid but may require justification. |
| I50.9 | Heart Failure, unspecified | Avoid if possible—specify I50.2x (systolic), I50.3x (diastolic), or I50.4x (combined). |
| E03.9 | Hypothyroidism, unspecified | Use E03.1 (congenital), E03.2 (drug-induced), or E03.8 (other specified) if documented. Labs alone don’t dictate coding—clinician’s diagnosis does. |
| M05.79 | Rheumatoid arthritis, multiple sites | Add laterality (M05.771, M05.772) if documented. For seropositive RA, use M05.7- series. |
What Are the Top Billing Challenges for Internal Medicine Practices?
Internal medicine providers face unique claim risks due to patient complexity and frequent Medicare interactions.
❌ Unspecified ICD-10 Codes: Denials from lack of clinical specificity.
❌ Undercoding E/M Levels: Loss of potential reimbursement due to billing lower than the documented complexity (e.g., 99213 vs. 99214).
❌ Telehealth Misbilling: Medicare and many payers require modifier -95 (synchronous telemedicine) or POS 02; rules vary by insurer (Verify payer requirements).
❌ Chronic Care Gaps: Many practices miss CCM (99490) or TCM eligibility; Medicare requires ≥2 chronic conditions expected to last ≥12 months or pose a significant risk (CCM) or 30-day post-hospital/SNF discharge care (TCM). (Document severity and track discharge dates)
❌ Documentation Deficiencies: Insufficient MDM, incomplete ROS, or missing time logs can downcode 99214 or disqualify 99490.
What Are the Best Practices to Improve Internal Medicine Billing Outcomes?
Implement these billing strategies to reduce denials and increase reimbursements:
✅ Use Code Scrubbers: Catch mismatches between CPT and ICD-10 before submission.
✅ Apply Modifiers Correctly: E.g., Use -25 for E/M + minor procedures.
✅ Audit Charts Regularly: Prevent downcoding and missed CCM eligibility.
✅ Train Staff on E/M Guidelines: Focus on MDM-based selection for 2025 rules.
✅ Use Automation for Eligibility & Tracking: Reduces claim rework and improves speed.
✅ Ensure Detailed Documentation: Support medical necessity with thorough clinical notes.
Following a billing compliance checklist reduces audit risk and enhances payer confidence.
✅ Stay Updated on Coding Changes: Monitor annual CPT, ICD-10, and payer policy updates.
✅ Strengthen Denial Management: Track trends, appeal efficiently, and prevent repeat denials.
✅ Improve Payer & Patient Communication: Clarify billing policies and resolve disputes faster.
What Are the Most Important Modifiers for Internists?
Modifiers ensure proper coding for services performed under special circumstances (e.g., same-day procedures, telehealth, or post-op care). Incorrect use triggers audits, so always tie modifiers to clear documentation.
| Modifier | Use Case & Why It Matters for Internists | Key Nuances & Pitfalls |
|---|---|---|
| -25 | E/M + procedure on the same day (e.g., office visit with joint injection). Critical for internists: Frequent need to bill separately for E/M when justified. | – Must show the E/M was significant and separately identifiable from the procedure (e.g., new problem addressed). – Audit risk: Overuse without documentation. |
| -95 | Real-time telehealth visits (e.g., video follow-up for chronic care). Internists: High telehealth use for chronic disease management. | – Use only for synchronous (live) video. – Avoid with phone-only (99441-99443) or asynchronous (e.g., -GQ) services. |
| -59 | Distinct procedural service (e.g., biopsy at two unrelated sites). Internists: Often bundle procedures (e.g., skin excisions, ECGs). | – Use only if procedures are separate encounters, anatomic sites, or sessions. – Better: Replace with -X{EPSU} (e.g., -XS for same organ system). |
| -GA | Medicare ABN on file (e.g., for non-covered services like routine labs). Internists: Common for preventive denials (e.g., “medically unnecessary” tests). | – Must have a signed ABN before service. – No ABN? Use -GZ (expect denial). |
| -24 | Unrelated E/M during post-op period (e.g., new UTI after surgery). Internists: Manages post-op complications unrelated to the procedure. | – Documentation must explicitly state the visit is unrelated to surgery. – Denial risk: If linked to post-op care. |
| -33 | Preventive service with waived cost-sharing (e.g., ACA-mandated screenings). Internists: Often provides Medicare Annual Wellness (G0438-9). | – Applies only to preventive services (e.g., colonoscopy for screening, not diagnostic). |
| -57 | Decision for surgery (e.g., pre-op eval for elective procedure). Internists: Key for referrals or surgical clearances. | – Use only if the E/M directly results in the decision to operate. – Do not use for minor procedures (e.g., suturing). |
What Tools Help Internal Medicine Billing Efficiency?
Specialty-driven software reduces billing errors and improves revenue cycle performance.
| Tool | Strengths |
|---|---|
| AdvancedMD | MDM-driven E/M coding, modifier prompts |
| Kareo | Built-in real-time eligibility checks and claim scrubbing |
| eClinicalWorks | TCM/CCM time tracking and care plan templates |
| DrChrono | Medicare-compliant AWV modules and telehealth integration |
| Athenahealth | Revenue optimization dashboards for internal medicine |
See the best billing software for internal medicine.
Frequently Asked Questions (FAQ’s)
1. What CPT code should I use for a moderate MDM follow-up?
Use 99214 if managing 2+ chronic conditions or spending 25+ minutes. Document MDM or time to avoid denials.
2. Can I bill G0439 and 99214 on the same day?
Yes, with modifier -25 on 99214 if services are separate and medically necessary. Document clearly.
3. What causes most claim denials for internal medicine?
Unspecified ICD-10 codes, missing time documentation, incorrect modifiers, and lack of medical necessity.
4. Does Medicare cover chronic care management (CCM)?
Yes, under 99490 for 20+ minutes/month managing 2+ chronic conditions. Requires patient consent and proper documentation.
Internal Medicine CPT/ICD Quick Reference Sheet
| Service Category | CPT Code Examples | ICD-10 Pairing Examples & Notes |
|---|---|---|
| E/M Office Visits (Established Patient) | 99213, 99214, 99215 | – I10 (High blood pressure) – E11.9 (Type 2 diabetes) – J44.9 (COPD) Use more specific codes if available. |
| Annual Wellness Visit (AWV) | G0438 (First visit) G0439 (Follow-up) | – Z00.00 (Normal check-up) – Z00.01 (Check-up with problems) Cannot bill with a routine physical on the same day. |
| Chronic Care Management (CCM) | 99490 (20+ min/month) 99487 (60+ min, complex) | – N18.3 (Kidney disease, Stage 3) – E11.22 (Diabetes + kidney disease) Must document care coordination. |
| Telehealth (E/M Visits) | 99214-99215 (with modifier) 99441 (Phone consult) | – F32.9 (Depression) – Z71.1 (Patient concern, no diagnosis) Check payer rules for telehealth coverage. |
| Diagnostics | 94010 (Spirometry) 93000 (ECG) 93306 (Echocardiogram) | – I50.9 (Heart failure) – I48.91 (Atrial fibrillation) Use specific codes when possible. |
Important Notes:
- CPT & ICD-10 codes change yearly—always verify the latest updates.
- Avoid unspecified codes (like J44.9, I50.9) if a more detailed diagnosis is known.
- Telehealth rules vary—some insurers require modifiers (e.g., 95, GT).
- Chronic Care Management requires monthly time tracking and documentation.
