Internal Medicine ICD-10 Codes & CPT Codes

Internists manage complex, multi-system conditions across adult patients. Precise ICD-10 coding for chronic disease management, acute presentations, and preventive care is essential for proper reimbursement. This page lists the top ICD-10-CM and CPT codes used in internal medicine practices.

FY 2026 ICD-10-CM (CMS) · CPT codes updated annually · All codes verified billable · Last verified: June 2026

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Top ICD-10 Codes for Internal Medicine

ICD-10 Code Description Billable
I10 Essential (primary) hypertension ✓
E08.9 Diabetes mellitus due to underlying condition without complications ✓
E09.9 Drug or chemical induced diabetes mellitus without complications ✓
E10.9 Type 1 diabetes mellitus without complications ✓
E11.9 Type 2 diabetes mellitus without complications ✓
E78.5 Hyperlipidemia, unspecified ✓
J44.1 Chronic obstructive pulmonary disease with (acute) exacerbation ✓
K21.9 Gastro-esophageal reflux disease without esophagitis ✓
I25.10 Atherosclerotic heart disease of native coronary artery without angina ✓
N18.3 Chronic kidney disease, stage 3 (moderate) ✓
I50.9 Heart failure, unspecified ✓
R73.09 Other abnormal glucose (prediabetes) ✓
E03.9 Hypothyroidism, unspecified ✓
M54.5 Low back pain ✓
F41.1 Generalized anxiety disorder ✓
Z87.891 Personal history of nicotine dependence ✓
R05 Cough ✓
Z00.00 Encounter for general adult medical examination without abnormal findings ✓
E11.65 Type 2 diabetes mellitus with hyperglycemia ✓
E11.40 Type 2 diabetes mellitus with diabetic neuropathy, unspecified ✓
E11.319 Type 2 diabetes mellitus with unspecified diabetic retinopathy without macular edema ✓
E13.9 Other specified diabetes mellitus without complications ✓
I48.91 Unspecified atrial fibrillation ✓
I48.0 Paroxysmal atrial fibrillation ✓
I11.9 Hypertensive heart disease without heart failure ✓
I12.9 Hypertensive chronic kidney disease with stage 1 through stage 4 or unspecified CKD ✓
N18.4 Chronic kidney disease, stage 4 (severe) ✓
N18.5 Chronic kidney disease, stage 5 ✓
J45.20 Mild intermittent asthma, uncomplicated ✓
J44.0 Chronic obstructive pulmonary disease with (acute) lower respiratory infection ✓
E66.01 Morbid (severe) obesity due to excess calories ✓
E66.9 Obesity, unspecified ✓
K57.30 Diverticulosis of large intestine without perforation or abscess without bleeding ✓
K58.9 Irritable bowel syndrome without diarrhea ✓
K76.0 Fatty (change of) liver, not elsewhere classified ✓
K70.10 Alcoholic hepatitis without ascites ✓
M81.0 Age-related osteoporosis without current pathological fracture ✓
E28.319 Polycystic ovary syndrome, unspecified ✓
D64.9 Anemia, unspecified ✓
D50.9 Iron deficiency anemia, unspecified ✓
F32.1 Major depressive disorder, single episode, moderate ✓
G47.33 Obstructive sleep apnea (adult) (pediatric) ✓
R53.83 Other fatigue ✓
Z13.6 Encounter for screening for cardiovascular disorders ✓

Source: CMS ICD-10-CM Official Code Set FY 2026

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Common CPT Codes for Internal Medicine Billing

CPT Code Description Medicare Rate* Common Modifiers
99202 New patient office visit, straightforward complexity ~$76 -25, -57
99203 New patient office visit, low complexity ~$112 -25, -57
99204 New patient office visit, moderate complexity ~$167 -25, -57
99205 New patient office visit, high complexity ~$207 -25, -57
99211 Office visit, established patient, minimal complexity (nurse visit) ~$24 -25
99212 Office visit, established patient, straightforward complexity ~$58 -25
99213 Office visit, established patient, low complexity ~$93 -25, -57
99214 Office visit, established patient, moderate complexity ~$133 -25, -57
99215 Office visit, established patient, high complexity ~$167 -25, -57
99417 Prolonged office visit, each additional 15 minutes beyond minimum time ~$35 -25
93000 Electrocardiogram, routine ECG with interpretation and report ~$18 -26, -TC
96372 Therapeutic, prophylactic, or diagnostic injection; subcutaneous or intramuscular ~$25 -59
99490 Chronic care management services, at least 20 minutes per calendar month ~$62 N/A
99483 Assessment of and care planning for patient with cognitive impairment ~$282 -25
G0438 Annual wellness visit (AWV), initial ~$173 N/A
G0439 Annual wellness visit (AWV), subsequent ~$116 N/A
99495 Transitional care management, moderate medical decision-making complexity, 30 days ~$165 -25

*Approximate 2025 CMS national non-facility rate. Rates vary by geography, setting, and payer contract. Refer to the CMS Physician Fee Schedule for official rates.

Top Denial Reasons for Internal Medicine Claims

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Medical Necessity Not Documented

Payers deny claims when the visit note does not clearly link the diagnosis to the service rendered or fails to document why a higher-complexity level was required. Ensure every chronic condition managed at the encounter is coded and supported by documentation of assessment and plan.

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Missing or Incorrect Modifier -25 for Same-Day Procedures

When an E/M visit (99213-99215) is billed on the same date as a procedure such as an ECG (93000) or injection (96372), modifier -25 must be appended to the E/M code to indicate a significant, separately identifiable service. Omitting -25 routinely triggers automatic bundling denials.

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Unspecified or Non-Specific Diagnosis Codes

Using unspecified codes such as E11.9 (Type 2 diabetes without complications) when the record documents complications (e.g., neuropathy, retinopathy, or CKD) results in downcoding and lost reimbursement under HCC risk adjustment. Code to the highest level of specificity supported by documentation.

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Prior Authorization Not Obtained for Chronic Care Management

Services billed under CCM codes (99490, 99491) and transitional care management (99495) are frequently denied when the patient enrollment consent, time documentation, or plan of care is missing from the record. Confirm payer-specific authorization requirements before billing these codes monthly.

Internal Medicine Billing & Coding Tips

  • Chronic conditions managed at the encounter should always be coded even if they are not the primary reason for the visit.
  • N18.3 (CKD stage 3) through N18.6 (ESRD) require documentation of the GFR stage from lab values — query the physician if the stage is undocumented.
  • Use I12.x or I13.x when hypertension and CKD coexist, replacing a simple I10 — CMS assumes a causal relationship.
  • Code tobacco use (Z72.0) and tobacco dependence (F17.2×0) accurately; they affect HCC risk adjustment under value-based contracts.

Frequently Asked Questions

When do I use I12 vs I10 for hypertension with CKD?

When a patient has both hypertension and CKD, ICD-10 assumes a causal relationship. Use I12.9 (Hypertensive chronic kidney disease with stage 1–4 CKD) instead of coding I10 and N18.x separately. Add the appropriate N18.x code to indicate the CKD stage.

What is R73.09 used for?

R73.09 (Other abnormal glucose) is the correct code for prediabetes or impaired fasting glucose. It is preferable to E11.9 when diabetes has not been diagnosed. Document it alongside lab values to support medical necessity for monitoring services.

How many chronic conditions can I list per encounter?

There is no limit. CMS and most commercial payers expect all chronic conditions managed or addressed at the encounter to be coded. This also impacts HCC risk adjustment scores for value-based payment models.

What is the correct code for GERD?

K21.9 is GERD without esophagitis (most common). K21.0 is GERD with esophagitis. Use K21.0 only when endoscopy or biopsy has confirmed esophagitis. The distinction matters for medical necessity review of PPI prescribing.

How does OmniMD support internal medicine documentation?

OmniMD’s Internal Medicine EHR features chronic disease management protocols, HEDIS measure tracking, and smart ICD-10 suggestions based on the patient’s active problem list.

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