ICD 10 Cheat Sheet 2026

The 30 highest-yield ICD 10 facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. In the Alphabetic Index, what do brackets [ ] around a code or term typically enclose? → Synonyms, alternative wording, or explanatory phrases
2. Which placeholder character is used in ICD-10-CM to fill empty positions when a 7th character is required? → X
3. When coding diabetes mellitus with an associated condition, ICD-10-CM generally uses: → A combination code linking the diabetes and the manifestation
4. What is the maximum number of characters an ICD-10-CM diagnosis code can contain? → 7
5. Under ICD-10-CM guidelines, when a patient is admitted for treatment of a complication of surgery, how should the complication be coded? → As the principal diagnosis if it is the reason for admission
6. What is the most effective study strategy for this type of exam? → Consistent study over time using active recall, practice tests, and spaced repetition
7. A combination code in ICD-10-CM is best described as a single code that does what? → Classifies two diagnoses or a diagnosis with an associated complication
8. Which external cause code category covers accidental falls in ICD-10-CM? → W codes (W00-W19)
9. ICD-10-CM is primarily used in the United States for which purpose? → Diagnosis coding and reporting
10. During an assessment, a 'Use additional code' note is present. This instructs the coder to: → Add a secondary code to provide a fuller picture
11. When a code requires a 7th character but the code is only 5 characters long, what must be used in positions 6? → The letter 'X' as a placeholder
12. In the inpatient setting, the principal diagnosis is defined as the condition: → Established after study to be chiefly responsible for admission
13. A symptom NOT routinely associated with the confirmed diagnosis should be: → Coded as an additional diagnosis
14. The external cause status code Y99.8 (Other external cause status) is assigned when the patient: → Was performing work but not military, recreational, or student activity
15. The instructional note 'Use additional code' in ICD-10-CM tells the coder to: → Add a secondary code to fully describe the condition
16. For coding HIV-related encounters, a patient with an HIV-related illness should be assigned: → B20 followed by codes for the related conditions
17. Z codes in ICD-10-CM are used primarily to report: → Factors influencing health status and contact with health services
18. The instructional note 'Code first' in ICD-10-CM directs the coder to do what? → Sequence the underlying condition before the manifestation
19. The following ICD-10 codes are used: → All of the above
20. External cause codes (Chapter 20, V00–Y99) in ICD-10-CM are: → Never reported as a principal/first-listed diagnosis
21. Payment status indicator C in Medicare's Outpatient Prospective Payment System (OPPS) indicates that the HCPCS is: → Only performed in inpatient settings
22. For inpatient coding, a diagnosis documented as 'probable' or 'suspected' at discharge should be: → Coded as if it existed
23. When should you change an answer during exam review? → Only when you have a clear, specific reason to believe the original answer was wrong
24. For a subsequent encounter during the healing phase of a fracture, the seventh character assigned is: → D – Subsequent encounter
25. The guideline 'Use additional code' typically signals the need to: → Identify a secondary condition such as an infectious organism
26. Z codes for contact with and exposure to communicable diseases are found in which ICD-10-CM category? → Z20
27. Which character position in an ICD-10-CM code is reserved for the seventh-character extension such as encounter type? → Seventh
28. What is the difference between ICD-10-CM and ICD-10-PCS? → CM is for diagnosis coding; PCS is for inpatient procedure coding
29. When a residual condition (sequela) requires coding but no specific sequela code exists, the coder assigns the: → Residual condition code followed by the cause code with 7th character 'S'
30. The seventh-character 'A' in an injury code most commonly indicates which encounter type? → Initial encounter