ICD-10 codes (International Classification of Diseases, 10th Revision) are alphanumeric codes that classify diseases, symptoms, and medical conditions for billing and clinical documentation. This searchable 2025 reference covers common diagnosis codes across all medical specialties — from pre-operative Z-codes and chronic disease codes to injury classifications — helping billers and coders reduce claim rejections caused by incorrect diagnosis coding.
| Code | Description | Category | Clinical Notes |
|---|---|---|---|
| A09 | Infectious gastroenteritis and colitis, unspecified | Infectious Disease | Stomach flu/viral gastroenteritis; specify organism when known. |
| B00.9 | Herpesviral infection, unspecified | Infectious Disease | HSV; use B00.1 for herpes simplex dermatitis, B00.2 for gingivostomatitis. |
| B34.9 | Viral infection, unspecified | Infectious Disease | General viral illness; use more specific codes when organism identified. |
| E03.9 | Hypothyroidism, unspecified | Endocrine | Common endocrine diagnosis; use E06.3 for autoimmune thyroiditis (Hashimoto's). |
| E11.65 | Type 2 diabetes mellitus with hyperglycemia | Endocrine | Indicates diabetes with documented hyperglycemia; important for demonstrating medical necessity of treatment adjustments. |
| E11.9 | Type 2 diabetes mellitus without complications | Endocrine | Use additional codes for specific complications: E11.65 (hyperglycemia), E11.21 (diabetic nephropathy), E11.40 (neuropathy). |
| E66.01 | Morbid (severe) obesity due to excess calories | Endocrine | BMI 40+; code BMI separately with Z68.4x codes. Often required for bariatric surgery authorization. |
| E78.5 | Hyperlipidemia, unspecified | Endocrine | General hyperlipidemia code; use E78.0 for pure hypercholesterolemia, E78.1 for hypertriglyceridemia. |
| F10.20 | Alcohol dependence, uncomplicated | Mental Health | Use additional codes for associated conditions; F10.21 for alcohol dependence in remission. |
| F32.1 | Major depressive disorder, single episode, moderate | Mental Health | Specify episode type and severity. F32.0 (mild), F32.2 (severe without psychotic), F33.x for recurrent episodes. |
| F41.1 | Generalized anxiety disorder | Mental Health | Common mental health diagnosis; distinguish from F41.0 (panic disorder), F41.9 (anxiety disorder, unspecified). |
| F90.0 | Attention-deficit hyperactivity disorder, predominantly inattentive type | Mental Health | ADHD-inattentive; F90.1 for predominantly hyperactive-impulsive, F90.2 for combined type. |
| G43.909 | Migraine, unspecified, not intractable, without status migrainosus | General | Use specific migraine codes when type is documented: G43.0 (without aura), G43.1 (with aura). |
| I10 | Essential (primary) hypertension | Cardiovascular | Most commonly billed diagnosis code; use for unspecified or primary hypertension. Do not use for hypertensive crisis (I16.x) or secondary hypertension. |
| I25.10 | Atherosclerotic heart disease of native coronary artery without angina pectoris | Cardiovascular | Coronary artery disease (CAD); use specific codes for bypass graft arteries or with angina. |
| I48.91 | Unspecified atrial fibrillation | Cardiovascular | Use more specific codes when type is known: I48.0 (paroxysmal), I48.1 (persistent), I48.2 (chronic/permanent). |
| I50.9 | Heart failure, unspecified | Cardiovascular | Use specific codes when type is known: I50.1 (left ventricular), I50.20-I50.23 (systolic), I50.30-I50.33 (diastolic). |
| J02.9 | Acute pharyngitis, unspecified | Respiratory | Sore throat; use J02.0 for streptococcal pharyngitis when confirmed by testing. |
| J06.9 | Acute upper respiratory infection, unspecified | Respiratory | Common cold/URI; one of the most frequently used diagnosis codes in primary care and urgent care settings. |
| J18.9 | Pneumonia, unspecified organism | Respiratory | Use when organism is unknown; code specific organism when identified (J13 for pneumococcal, J15.x for bacterial). |
| J44.1 | Chronic obstructive pulmonary disease with acute exacerbation | Respiratory | COPD exacerbation; J44.0 for COPD with acute lower respiratory infection, J44.9 for unspecified COPD. |
| J45.20 | Mild intermittent asthma, uncomplicated | Respiratory | Classify asthma severity: mild intermittent (J45.2x), mild persistent (J45.3x), moderate persistent (J45.4x), severe persistent (J45.5x). |
| K21.0 | Gastro-esophageal reflux disease with esophagitis | Gastrointestinal | GERD with esophagitis; K21.9 for GERD without esophagitis. |
| K58.9 | Irritable bowel syndrome without diarrhea | Gastrointestinal | IBS; K58.0 for IBS with diarrhea, K58.1 for IBS with constipation. |
| K80.20 | Calculus of gallbladder without cholecystitis | Gastrointestinal | Gallstones without inflammation; K80.00 with acute cholecystitis, K80.10 with chronic cholecystitis. |
| L50.9 | Urticaria, unspecified | General | Hives/allergic rash; specify L50.0 for allergic urticaria when allergy is documented. |
| M17.11 | Primary osteoarthritis, right knee | Musculoskeletal | Common in orthopedic and primary care; laterality required. M17.12 for left knee, M17.0 for bilateral. |
| M23.611 | Other spontaneous disruption of anterior cruciate ligament, right knee | Musculoskeletal | ACL tear; specify laterality and type of tear (partial vs. complete) when documented. |
| M25.511 | Pain in right shoulder | Musculoskeletal | Laterality must be specified for shoulder pain. Use M25.512 for left shoulder, M25.519 for unspecified. |
| M54.2 | Cervicalgia | Musculoskeletal | Neck pain; use M54.2 for pain without radiculopathy. Add M50.x codes for cervical disc disorders. |
| M54.5 | Low back pain | Musculoskeletal | One of the most common reasons for office visits; specify chronicity with M54.50 (unspecified) or laterality when known. |
| M79.3 | Panniculitis, unspecified | Musculoskeletal | Inflammation of subcutaneous fat; specify site when possible. |
| N39.0 | Urinary tract infection, site not specified | General | UTI unspecified; use B96.2x for specific organism. N30.0 for acute cystitis, N10 for acute pyelonephritis. |
| R05.9 | Cough, unspecified | Respiratory | Symptom code; link to underlying diagnosis when established. R05.1 for acute cough, R05.3 for chronic cough. |
| R10.9 | Unspecified abdominal pain | General | Use more specific codes when location is known: R10.0 (acute abdomen), R10.1 (upper), R10.3 (lower). |
| R51.9 | Headache, unspecified | General | Use as initial presentation; transition to specific diagnosis (migraine, tension) when confirmed. |
| Z00.00 | Encounter for general adult medical examination without abnormal findings | General | Annual physical exam; add Z-codes for screening services performed during the visit. |
| Z12.31 | Encounter for screening mammogram for malignant neoplasm of breast | General | Screening mammography; covered at 100% as preventive service under most plans. |
| Z23 | Encounter for immunization | General | Primary diagnosis for vaccine administration; add codes for specific vaccines given. |
| Z87.891 | Personal history of nicotine dependence | General | Former smoker/tobacco user; Z72.0 for current tobacco use, F17.2x for current nicotine dependence. |