How to Use the ICD-10-CM Guidelines as a Beginner

If you’re new to medical coding, the ICD-10-CM guidelines can feel overwhelming at first glance. With hundreds of pages, rules, conventions, and coding instructions, it’s easy to get confused. But here’s the good news: once you understand how the guidelines are structured and how to apply them, coding becomes much easier—and far more accurate.

In this beginner-friendly guide, we’ll break down how to use the ICD-10-CM Official Guidelines step by step, so you can confidently code diagnoses in any clinical setting. Know More

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What Are the ICD-10-CM Guidelines?

The ICD-10-CM Official Guidelines for Coding and Reporting are a set of rules developed by the CDC and CMS. They explain how to assign diagnosis codes correctly, how to interpret code descriptions, and how to apply coding conventions.

You should use the guidelines every time you code. They ensure:

• Accuracy
• Consistency
• Compliance
• Proper reimbursement

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Why Beginners Need the Guidelines

Many new coders rely only on the code book index and forget the rules that accompany them—which leads to errors like:

• Using the wrong laterality
• Missing combination codes
• Overcoding or undercoding
• Misinterpreting symptoms vs. confirmed diagnoses

The guidelines act as your instruction manual for coding correctly.

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How the ICD-10-CM Guidelines Are Organized

To use the guidelines effectively, it’s important to understand their structure. They are divided into four main sections:

Section I – Conventions, General Coding Guidelines & Chapter-Specific Guidelines

This section covers:

• Basic notations (NEC, NOS, “code first,” “use additional code”)
• How to use the Index and Tabular List
• Chapter-specific rules (e.g., diabetes, pregnancy, injuries)

Section II – Selection of Principal Diagnosis

Used mainly for inpatient coding. It explains how to choose the main diagnosis after study.

Section III – Reporting Additional Diagnoses

Clarifies when you can and cannot assign secondary diagnoses.

Section IV – Diagnostic Coding for Outpatient Services

Rules specific to office visits, urgent care, ED, etc.

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Step-by-Step Guide: How to Use ICD-10-CM Guidelines as a Beginner

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Step 1: Always Start With the Provider’s Documentation

The guidelines emphasize one thing repeatedly:

Code only what is documented by the provider.

Before touching the code book:

• Identify the chief complaint
• Look for diagnoses, signs, symptoms
• Review lab/imaging results only if the provider interprets them

Never make assumptions.

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Step 2: Start With the Index, Not the Tabular List

Beginners often jump straight to the Tabular List, but the guidelines state:

Always begin in the Alphabetic Index.

Here’s how:

1. Look up the main term (e.g., “Diabetes,” “Fracture,” “Asthma”)
2. Follow the subterms for specificity
3. Note the suggested code

This is only the first step—the Tabular List will confirm.

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Step 3: Verify the Code in the Tabular List

The Tabular List contains:

• Code descriptions
• Notes and instructions
• Excludes1 and Excludes2 rules
• “Includes,” “Use Additional Code,” and “Code First” notes
• Laterality and severity details

Never assign a code without checking it in the Tabular List.

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Step 4: Apply Conventions and Notes

This is where accuracy comes in.

Important conventions include:

Excludes1

Two conditions cannot be coded together.

Excludes2

Both conditions may be coded if present.

Code First

Some conditions must be sequenced first.

Use Additional Code

Another code is required for full classification (e.g., drug use, organism type, complications).

Combination Codes

One code may describe:

• The condition
• Its manifestation
• Its complications

Conventions are a major part of accurate coding—don’t skip them.

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Step 5: Follow Chapter-Specific Guidelines

Each ICD-10-CM chapter has rules unique to that type of condition.

Examples:

Endocrine (E00–E89) – Diabetes

• Requires severity
• Body system affected
• Complications
• Type of diabetes

Infectious Diseases (A00–B99)

• Sequence the causal organism if known
• Use additional codes for drug resistance

Pregnancy, Childbirth & Puerperium (O00–O9A)

• Always code from Chapter 15 first
• Use trimester-specific codes

Each chapter has its own rules—these are essential.

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Step 6: Pay Attention to Laterality and Specificity

ICD-10-CM demands specificity. Look for:

• Left, right, bilateral
• Episode of care
• Severity
• Anatomical site

If documentation lacks detail, query the provider (if allowed in your role).

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Step 7: Never Code Probable, Suspected, or Rule-Out Diagnoses (Outpatient)

Per Section IV:

Outpatient coding uses signs and symptoms when diagnoses are not confirmed.

For example:
“Rule out pneumonia” → Code cough, fever, shortness of breath, etc.

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Step 8: Update Your Guidelines Every Year

ICD-10-CM is updated every October 1.

New coders must get into the habit of:

• Downloading new guidelines
• Reviewing code changes
• Retiring outdated codes

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Tips for Beginners to Master the Guidelines

• Practice on real clinical scenarios
• Highlight important conventions
• Create a cheat sheet for common notes
• Study one chapter at a time
• Use official sources: CMS, CDC, AAPC, AHIMA

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Conclusion

The ICD-10-CM guidelines are the backbone of accurate medical coding. As a beginner, mastering them will build your confidence, reduce errors, and set you up for success in any coding role.

With consistent practice and a solid understanding of how the guidelines work, you’ll quickly become a more accurate, reliable, and professional medical coder.