# How to Use the Alphabetic Index and Tabular List in ICD-10-CM

URL: https://icdcodefinder.com/blog/how-to-use-the-alphabetic-index-icd-10-cm  
Published: 2026-11-02  
Updated: 2026-11-02  
Author: Priya Raman, CPC, CCS-P — Code Set & Tools Editor (ICD Code Finder editorial pen name)  
Category: Coding Tools & Tips  
ICD-10-CM codes: E11, E11.65, I10, I11.0, I50, I50.9, J18.9, T36, T65, V00, Y99, Z79.4  

> A step-by-step ICD-10-CM lookup workflow: find the main term in the Alphabetic Index, read subterms and cross-references, then verify every code and note in the Tabular List.

## Key takeaways

- Every ICD-10-CM lookup starts with the documented condition as a main term in the Alphabetic Index, not the anatomic site.
- Nonessential modifiers in parentheses do not change the code, but indented subterms do, so read every subterm level carefully.
- Follow "see" instructions every time and check "see also" when the original main term does not lead to a specific code.
- Section I.B.1 of the Official Guidelines requires verifying every Index code in the Tabular List, where laterality, 7th characters and instructional notes live.
- Tabular notes such as Excludes1, Code first, Use additional code and Code also can change or add to the final code set you report.
- Use the current fiscal year Index and Tabular List, which for FY2027 took effect October 1, 2026.

If you are learning how to use the Alphabetic Index, the core rule is simple. Look up the documented condition as a main term in the ICD-10-CM Alphabetic Index, follow its subterms and cross-references to a tentative code, then verify that code in the Tabular List before you assign it. The Index points you to a code; the Tabular List confirms it and adds the instructions the Index leaves out.

This guide walks through that workflow step by step for the FY2027 code set, which took effect October 1, 2026. It is written for coding students and newer coders, but it also works as a refresher for CDI and billing staff. It is educational content, not billing-compliance advice, so always follow the official guidelines, payer policies and provider documentation.

## Why does ICD-10-CM coding start in the Alphabetic Index?

ICD-10-CM has tens of thousands of codes. Nobody can scan the Tabular List chapter by chapter to find the right one. The Alphabetic Index solves that problem by listing diagnostic terms in alphabetical order, each with a code or a pointer to one.

The ICD-10-CM Official Guidelines for Coding and Reporting make the sequence explicit. Section I.B.1 says to first locate the term in the Alphabetic Index and then verify the code in the Tabular List. It also states that it is essential to use both, because the Index does not always provide the full code.

Think of the two parts this way:

- **Alphabetic Index:** a search tool organized by condition names, eponyms and reasons for encounter.
- **Tabular List:** the authoritative classification, organized by chapter and category, with all instructional notes.

You can browse both in ICD Code Finder: the [ICD-10-CM Alphabetic Index](/index) and the [Tabular List by chapter](/chapters).

## How do you find the right main term for a diagnosis?

Main terms in the Index are mostly conditions, not body sites. Look up "Pneumonia," "Fracture" or "Disease," not "Lung," "Femur" or "Kidney." The anatomic site usually appears as a subterm beneath the condition.

Use these rules of thumb to pick the main term:

1. **Identify the condition word.** In "acute bacterial pneumonia," the condition is pneumonia.
2. **Try the noun form first.** Look up "Hypertension," then read the subterms for "heart," "kidney" and so on.
3. **Check eponyms.** Many syndromes and diseases named for a person are main terms under the eponym.
4. **Use encounter terms for Z codes.** Main terms such as "History," "Status," "Screening," "Examination," "Encounter" and "Admission" lead to factors influencing health status.
5. **Try a synonym if the first term fails.** If "Insufficiency" does not get you there, try "Failure" or "Disease."

When documentation uses a vague phrase, the default code applies. Under Section I.A.18, the code listed next to a main term is the default for that condition when no further detail is documented. For example, the main term "Pneumonia" defaults to [J18.9](/icd10/J18.9) (Pneumonia, unspecified organism).

## What do nonessential modifiers, subterms and cross-references mean?

This is the heart of how to use the Alphabetic Index well. Index entries have a layered structure, and each layer tells you something different.

### What are nonessential modifiers?

Nonessential modifiers are words in parentheses right after a term. They may be present or absent in the diagnostic statement without changing the code.

Hypertension is the classic example. The main term lists modifiers such as (accelerated) (benign) (essential) (malignant) and points to [I10](/icd10/I10), Essential (primary) hypertension. Whether the provider writes "benign hypertension" or just "hypertension," the code is the same.

### What are subterms?

Subterms are indented under a main term. Unlike nonessential modifiers, they are essential: they describe a type, site, cause or circumstance that changes the code.

Read every indentation level. A second-level subterm under "type 2" under "Diabetes" means something different from a subterm sitting directly under "Diabetes."

### How do "with" and "in" work in the Index?

Section I.A.15 explains that "with" or "in" means "associated with" or "due to" in the Index and Tabular List. The classification presumes a causal link between conditions connected by these terms, unless the documentation clearly states they are unrelated or another guideline requires explicit linkage.

Note that the "with" subterm appears immediately under the main term, not in alphabetical order. New coders often miss it because they expect strict alphabetization.

### What do "see" and "see also" instructions mean?

Section I.A.16 covers these cross-references:

- **"See"** is mandatory. It tells you to go to another main term because the term you used does not hold the code.
- **"See also"** is optional. It tells you another main term may offer additional entries. You do not have to follow it if the original main term already gives you the code you need.

### Quick reference: Index conventions

| Index element | What it looks like | What it means | What you do |
|---|---|---|---|
| Main term | Bold, flush left | The condition or reason for encounter | Start your lookup here |
| Nonessential modifier | Words in parentheses | Does not affect the code | Ignore for code selection |
| Subterm | Indented under main term | Changes the code | Match it to documentation |
| "With" / "in" | Listed first under the main term | Presumed causal link | Check before other subterms |
| "See" | Cross-reference | Required redirection | Always follow it |
| "See also" | Cross-reference | Possible extra entries | Follow when needed |
| Dash (-) at end of code | Incomplete code | More characters required | Finish the code in the Tabular List |
| NEC | "Not elsewhere classifiable" | No specific code for the documented detail | Verify the "other" code |

## How do you use the Neoplasm Table, Table of Drugs and External Cause Index?

The ICD-10-CM Index includes more than the main alphabetic list. Knowing how to use the Alphabetic Index also means knowing when to jump to its tables.

### Neoplasm Table

The Neoplasm Table lists anatomic sites down the rows. Columns show behavior: malignant primary, malignant secondary, carcinoma in situ, benign, uncertain behavior and unspecified behavior.

Do not go to the table first if the documentation names a histologic type. Look up the morphology term, such as "Adenoma" or "Carcinoma," in the main Index. It will tell you which column to use or point to a specific code. Then go to the site in the table.

### Table of Drugs and Chemicals

This table lists substances alphabetically. Columns cover poisoning (accidental, intentional self-harm, assault, undetermined), adverse effect and underdosing. The codes fall in categories T36 through T65.

These codes require a 7th character for the encounter (initial, subsequent or sequela). The table does not supply it. You must add it from the Tabular List, along with any placeholder X.

### External Cause of Injuries Index

External cause codes (V00-Y99) have their own separate index. Use it to find how an injury happened, the place of occurrence, the activity and the external cause status. As with every other part of the Index, verify each code in the Tabular List.

## Why must every Index code be verified in the Tabular List?

The Index is a pointer, not a final answer. Section I.B.1 says selection of the full code, including laterality and any applicable 7th character, can only be done in the Tabular List. It also notes that a dash at the end of an Index entry means additional characters are required.

Verification catches problems the Index cannot show:

- **Incomplete codes.** The Index may list only a category or subcategory.
- **Billable status.** Only codes at the highest level of detail can be reported.
- **Exclusions.** Excludes1 and Excludes2 notes appear only in the Tabular List.
- **Sequencing instructions.** Code first and Use additional code notes live in the Tabular List.
- **Context.** Seeing nearby codes may reveal a more specific option the documentation supports.

To verify code in tabular list entries quickly, open the code page in ICD Code Finder, for example [E11.65](/icd10/E11.65). Each page shows the full title, billable status, Excludes notes, Code first / Use additional code / Code also notes and 7th-character rules.

### Worked example: type 2 diabetes with hyperglycemia

Documentation: "Type 2 diabetes mellitus with hyperglycemia. Patient on long-term insulin."

1. **Index:** Look up the main term "Diabetes, diabetic." Go to the subterm "type 2," then "with," then "hyperglycemia." The Index points to E11.65.
2. **Tabular:** Confirm [E11.65](/icd10/E11.65) is Type 2 diabetes mellitus with hyperglycemia and that it is billable.
3. **Read the category notes:** Category E11 instructs you to use an additional code to identify control, including insulin.
4. **Add the code:** Report [Z79.4](/icd10/Z79.4), Long term (current) use of insulin, as the documentation supports it.

If you had stopped at the Index, you would have missed the second code.

## Which Tabular notes change the final code you assign?

Several instructional notes in the Tabular List can change, add to or block the code you found in the Index. Check notes at the code, subcategory, category, block and chapter levels, because notes at a higher level apply to everything beneath them.

| Tabular note | What it tells you | Effect on your final codes |
|---|---|---|
| Excludes1 | The two conditions are never coded together (with limited exceptions in Section I.A.12.a) | May force a different code |
| Excludes2 | The excluded condition is not part of this code | You may report both if both exist |
| Code first | Underlying condition must be sequenced first | Adds a code and sets order |
| Use additional code | Another code adds needed detail | Adds a code |
| Code also | Another code may be needed; sequencing depends on circumstances | May add a code |
| 7th character | Required extension for the category | Completes the code |
| Placeholder X | Fills empty character positions | Needed before the 7th character |

### Worked example: hypertensive heart disease with heart failure

Documentation: "Hypertensive heart disease with chronic heart failure."

The Index entries under "Hypertension" lead to [I11.0](/icd10/I11.0), Hypertensive heart disease with heart failure. In the Tabular List, I11.0 carries a note to use an additional code to identify the type of heart failure (I50.-). You then return to the documentation to choose the most specific heart failure code it supports. If the type is not documented, that may be [I50.9](/icd10/I50.9), Heart failure, unspecified, or a CDI query opportunity.

For a deeper look at specificity gaps, see [heart failure documentation specificity and CDI queries](/blog/heart-failure-documentation-specificity-cdi-query). For exclusion notes, read [Excludes1 vs Excludes2 explained](/blog/excludes1-vs-excludes2-icd-10-cm-exclusion-notes).

## How to use the Alphabetic Index: a repeatable lookup workflow

Here are the ICD-10 code lookup steps in one checklist you can keep at your desk:

1. **Read the full documentation** and identify the condition, site, type, cause and encounter details.
2. **Choose the main term** for the condition, not the body site.
3. **Scan nonessential modifiers** but do not let them drive code selection.
4. **Read the "with" subterms first**, then work down the indented subterms that match the documentation.
5. **Follow every "see" instruction** and check "see also" when needed.
6. **Use the correct table** for neoplasms, drugs and chemicals or external causes.
7. **Go to the Tabular List** and confirm the code title matches the documentation.
8. **Complete the code** with any required characters, placeholder X and 7th character.
9. **Read all instructional notes** at every level and apply them.
10. **Check the guidelines** for chapter-specific rules before finalizing.

If you want a fast second opinion on a guideline question, the [guidelines chat tool](/ai/guidelines-chat) lets you ask about the Official Guidelines using your own AI key. AI answers must still be checked against the official text by a qualified coder.

## What common Index lookup mistakes should coders avoid?

Most lookup errors come from skipping a step, not from a lack of knowledge. Watch for these:

- **Coding from the Index alone.** This is the most common and most serious error. Always verify.
- **Coding from memory.** Codes and notes change each fiscal year. Check the [FY2027 new, revised and deleted codes](/updates) before relying on a familiar code.
- **Starting with the anatomic site.** Look up the condition, then find the site as a subterm.
- **Confusing modifiers with subterms.** Parenthetical words do not change the code; indented subterms do.
- **Skipping "with."** It sits at the top of the subterm list and is easy to overlook.
- **Ignoring "see" instructions.** If the Index says "see," the code is not under your current term.
- **Going straight to the Neoplasm Table.** Check the morphology term in the main Index first.
- **Dropping the 7th character.** Injury, poisoning and many other codes are invalid without it.
- **Missing category-level notes.** A Use additional code note at the category applies to every code under it.
- **Using an outdated code book.** For dates of service on or after October 1, 2026, use the FY2027 files.

CDI teams who find documentation gaps during lookup can draft compliant questions with the [CDI query builder](/ai/query-builder). For wording ideas, see these [compliant physician query examples](/blog/compliant-physician-query-examples-cdi-templates).

## How do digital tools fit into Index and Tabular lookups?

Digital lookup tools speed up the same workflow. They do not replace it. The official ICD-10-CM files from the [CDC National Center for Health Statistics](https://www.cdc.gov/nchs/icd/icd-10-cm/index.html) remain the source of truth, alongside payer policies and provider documentation.

In ICD Code Finder you can search terms on the [free ICD-10-CM code search](/search), browse the Index and Tabular List, and save frequently used codes with the [Code Set Builder](/code-sets). The [Note to Codes tool](/ai/note-to-codes) can suggest candidate codes from a clinical note with your own AI key. Treat every suggestion as a starting point to verify in the Index and Tabular List, never as a final answer.

## Next steps

Practice the workflow on a few real cases this week. Start with the main term, work through the subterms, then confirm every code and note in the Tabular List.

- [Look up codes free](/search) and open each code page to check its notes.
- Browse the [Alphabetic Index](/index) and the [Tabular List chapters](/chapters) side by side.
- Review the [FY2027 code updates](/updates) so your lookups reflect the current year.
- Find more practical guides in [Coding Tools & Tips](/blog/category/coding-tools-and-tips).

## Frequently asked questions

**Can I assign a code directly from the ICD-10-CM Alphabetic Index?**

No. The Official Guidelines require you to locate the term in the Alphabetic Index and then verify the code in the Tabular List. The Index does not always give the full code, and it does not show Excludes notes, Code first instructions or 7th-character requirements.

**What is the difference between a nonessential modifier and a subterm?**

A nonessential modifier appears in parentheses after a term and does not affect the code, whether or not it is documented. A subterm is indented under the main term and describes a different type, site or circumstance, so it usually changes the code assigned.

**What does a dash at the end of an Alphabetic Index entry mean?**

A dash means the code shown is incomplete and additional characters are required. You must go to the Tabular List to select the remaining characters, such as laterality, episode of care or other specificity.

**Do I always have to follow a "see also" instruction?**

Not always. A "see also" note tells you another main term may provide additional useful entries. If the original main term already leads you to a specific, supported code, following the "see also" reference is not required, though checking it is good practice.

**Are the Neoplasm Table and Table of Drugs and Chemicals part of the Alphabetic Index?**

Yes. Both tables are part of the ICD-10-CM Index, along with the separate External Cause of Injuries Index. Codes found in the tables must still be verified in the Tabular List like any other Index entry.

**Does the Alphabetic Index change every year?**

Yes. The Index is updated with each fiscal year release alongside the Tabular List, so new terms, revised paths and new codes appear annually. For dates of service on or after October 1, 2026, use the FY2027 Index and Tabular List.

**Can AI coding tools replace the Index-to-Tabular lookup?**

No. AI tools can suggest candidate codes and speed up research, but the suggestions must be reviewed by a qualified coder. You still need to confirm each code against the Index, Tabular List, Official Guidelines and provider documentation.

---

Disclaimer: ICD Code Finder is an informational tool and is not a substitute for professional coding judgment, payer policy, or the official ICD-10-CM classification and guidelines. Not affiliated with, endorsed by, or sponsored by CMS, NCHS, or the World Health Organization. AI suggestions require review by a qualified coder.