Master ICD-10-CM Codes by the Chapter Letters

This post was revised on 12/16/2022 to reflect the ICD-10-CM code changes for FY 2023.

master ICD-10-CM codes by the chapter letters

Did you know there is a way to master ICD-10-CM codes by the chapter letters? Obviously, there is no way to remember all of the codes in ICD-10-CM, especially since there are 73,207 of them. There is a strategy, however, that you can use that will get you into the right ballpark, so to speak.

In another post, I covered the highlights of the coding changes for FY 2023 that took effect on October 1, 2022.

In this article, I explain how to master ICD-10-CM codes by the chapter letters and provide you with a fantastic cheat sheet for quick reference. You will love it!

ICD-10-CM Codes (FY 2023)

The ICD-10-CM coding updates for the fiscal year 2023 took effect on October 1, 2022, and are valid until September 30, 2023, according to the Centers for Disease Control and Prevention (CDC).

The new code set includes 1,176 new codes, 28 revised codes, and 287 deleted codes. The biggest changes are associated with motorcycle and electric bike accidents, maternal care for fetal disorders, endometriosis, head injuries (including concussions), and dementia.

Be sure to review the ICD-10-CM Official Guidelines for Coding and Reporting, as they were also updated for FY 2023.


Although it is impossible for a medical coder to memorize all the ICD-10-CM codes, there is a way to get you close. That’s what Laurie Johnson states, and I agree. It’s called mnemonics.

Mnemonics is a strategy used to help improve your memory and learn important information.

Let me explain:

In ICD-10-CM, the first digit of each code is an alpha character. By using mnemonics, you can connect the first letter of a diagnosis code with the corresponding ICD-10-CM chapter. This will not only make it easier for you to find the first letter of the ICD-10-CM code, but it will also make it quicker.

And time is critical when you are taking a medical coding exam!

That’s why I have created an ICD-10-CM Chapter Cheat Sheet, which you can sign up for down below.

Chapters in ICD-10-CM

There are currently 22 chapters in ICD-10-CM for FY 2023. The codes range from A00 to Z99 and are described below. 

list of 22 chapters of ICD-10-CM, their chapter titles and code ranges
22 Chapters in ICD-10-CM for FY 2023.

Things to Keep in Mind – ICD-10-CM

Some things to note as it relates to the codes in ICD-10-CM:

  • Each code starts with a letter.
  • Each letter is associated with a specific chapter in ICD-10-CM.
  • Some chapters have more than one letter, such as Chapters 1 (A, B), 2 (C, D), 19 (S, T), and 20 (V, W, X, Y).
  • Some chapters share beginning letters, such as Chapters 2 and 3 (D) and Chapters 7 and 8 (H).

Once you learn the associated mnemonic for each chapter, you will be able to determine the appropriate chapter for a given code.

The mnemonic for each chapter is listed on the ICD-10-CM Chapter Cheat Sheet that I am providing through the signup form.

For additional information about the specific types of codes that can be found in each chapter, refer to your current ICD-10-CM coding manual.

Mnemonic Examples

Here are some examples to help you better understand how mnemonics will help you determine the first letter and chapter for each code.

Example #1

The mnemonic for Chapter 9, Diseases of the circulatory system (I00-I99), is “Infarction.” Think myocardial infarction or heart attack. This relates to the circulatory system. Therefore, a code related to the circulatory system begins with the letter “I.”

Taken from a different angle, if we see code I10, we immediately know that this code relates to the circulatory system. How do we know this? We know this based on the first letter “I.” And if we look up I10 in the ICD-10-CM coding manual, I10 refers to Essential (primary) hypertension. Hypertension is high blood pressure, and it pertains to the heart, or circulatory system (Chapter 9).

Example #2

The mnemonic for Chapter 4, Endocrine, nutritional and metabolic diseases (E00-E89), is “Endocrine.” If we see an exam question with E11.65 as one of the possible answers, we can see from the first letter “E” that it relates to the endocrine system. When looking up E11.65, it takes us to Type 2 diabetes mellitus with hyperglycemia.

Type 2 diabetes mellitus is a disorder of the endocrine system, and hyperglycemia is a complication of diabetes. Therefore, it makes sense that the first letter is “E“.

Example #3

A patient is diagnosed with major depressive disorder, recurrent, mild.

If I know my mnemonics, even before I look up the code for this diagnosis, I know that the first letter of the code is an “F“. The reason I know this is because the mnemonic for Chapter 5, Mental, behavioral, and neurodevelopmental disorders (F01-F99), is “Feelings of hopelessness.” The first letter is “F,” and depression codes are located in Chapter 5.

I can verify this by looking up the code in the Alphabetic Index under disorder, depressive, major, recurrent, F33 Major depressive disorder, recurrent. In the Tabular, F33.0 can be verified as Major depressive disorder, recurrent, mild.

Download the Free Cheat Sheet

Hopefully, now you get the idea of how mnemonics work for mastering ICD-10-CM codes by the chapter letters. And once you have the ICD-10-CM Chapter Cheat Sheet with all of the mnemonics listed, it should be even more clear and make things much easier.

To download the free cheat sheet, complete the form below. And if you like it — and I believe you will — please let me know down below in the comments and share it with others who may benefit from it.

Note: This Chapter Cheat Sheet is the same one I offered for FY 2022. No changes have been made.

How mnemonics make it quicker and easier to save time on the next medical coding exam.

That’s not all! After you have reviewed this information and downloaded the chapter cheat sheet, be sure and take the short quiz to find out if you are a true ICD-10-CM Medical Coding Expert!

If you like this article, please share it.


      1. Hi Marcheri,

        I understand that it can be hard to retain new information, especially when there may be a lot coming at you at once. Some things that have helped me, no matter what I’ve been learning, are to try to pick a designated place in my home that is quiet without distractions and I only focus on one topic at a time; study at a time of day or night that I am my sharpest (if my schedule allows); take notes and write things in my own words to help retain it better; take plenty of breaks; get plenty of sleep.

        Depending on your learning style, you may prefer to read and see images, listen to others explain, or you may prefer to learn by doing hands-on activities. I am a combination of all of these, so I appreciate a variety of ways to learn and retain information.

        As far as specific tips as they relate to your medical coding education, I would say the main thing is to know your coding guidelines and know where to find the information in your coding manuals. You can’t memorize everything. Tab your books, write any notes in the margins, and use highlighters to emphasize the important information.

        I kind of looked at my manuals like my bible when I was learning and preparing for the certification exam. And practice, practice, practice. Apply what you have learned to as many coding quizzes as you can take.

        When you do sit for the certification exam, remember it is timed. You are not expected to code as you would do in a real-world situation. You will be given multiple-choice questions.

        As an example, a coding scenario reads that a patient has been diagnosed with external hemorrhoids, and the choices are A) K64.4; B) J44.9; C) J18.9; D) K64.1, K57.30. If we know our chapters based on the first letter, we know that we can quickly eliminate B and C because those two codes are located in the respiratory system chapter (think “J” for junk in the lungs), and codes for hemorrhoids are located in the digestive system chapter (think “K” for Kaopectate).

        I hope this helps.

        1. My suggestion is to use flash cards,also my best time to study was alway just before I went to sleep because you can sleep on what study. It always helped me.

          1. Hey Teresa. Great suggestions. Flashcards always helped me too, and going to sleep with things fresh may work for a lot of people too.

            Thank you for your great feedback.

          1. Lisa, there is no particular way you have to tab your books. It really is a matter of preference. But just make sure that you use plastic tabs and not paper tabs, because paper tabs are not allowed during the certification exam. The purpose of the tabs is to help you find the information quickly during the exam, so know your books inside and out. Add pre-printed tabs or create your own. Some people prefer to add the tabs to the right-hand side of the pages, some like to add them to the top or bottom of the pages, and some use a combination of placement. So do whatever you feel most comfortable with. I used some on the sides and some on the top. Also, I found that using too many tabs would just slow me down, so be somewhat strategic about it. Between the tabs and highlighting certain information that I knew I would need to know on the exam really helped. Good luck on the exam!

  1. Do you have any suggestions for specific things that we should include in the notes inside our ICD-10-CM manual? Do you have a list for that also? That is something that I would be very interested in.

    1. Hi Cheryl,

      It would be difficult for me to list here specifically what all I wrote in my manuals to prepare for the CPC exam. However, at the time, I enrolled in CCO’s (CertificationCoachingOrg) Review Blitz course. It not only taught me how to bubble and highlight in my manuals, but it also included the types of notes to add throughout. I recommend their course without hesitation.

        1. Pamela, I currently have the AAPC coding manual for ICD-10-CM, but there are others. They will all give you this same information. The course you are taking now probably has a particular manual they are using that you will need to buy. I would check with them. As far as sitting for the CPC certification exam, you are allowed to bring the ICD-10-CM coding manual of your choice, but you want to have the current year.

  2. Thank you so much for this! I am starting all over again and learning this coding and billing is fun but alot of information! This really helped me! You’re awesome!

    1. Hi Pamela.

      You are so welcome! I’m glad it’s helping you. There is a lot to learn in this field, for sure. I think that’s why you have to really love it to stick with it.

      Have a great night!

  3. This is really helpful Debbie. You are right knowing Mnemonics, helps you save a lot of your time coding.

  4. Thanks for the updates!!!…I’m a newbie,currently studying to take CPC early 2021.I appreciate all the information that will help me pass.

  5. hi debbie i am new for coding how to find correct code from chart please explain simple method

    thanks & regards,

    1. Hi Chiranjeevi,

      I provided some examples in my post on how to determine the right Chapter where the code would be found. To find the exact code, however, you would need to look it up in the Alphabetic Index first and then verify it in the Tabular List. I hope this helps.

  6. Hi Debbie Jones,

    I am studying the Text book 21 Chapters of ICD-10. It is 730 pages, so many information. How can i memorize? How can I study it fast? especially the theory.

    1. Hi Alex,
      I don’t think there is a fast way to study ICD-10-CM, but I’ll try to tell you some things to focus on based on what I did. Read the first pages in the coding manual. Know the code structure; the layout of the manual and chapter structure; key words, medical terms, and abbreviations related to ICD-10-CM coding; coding guidelines and conventions; and the process for looking up and verifying main terms and subterms. Highlight important details in your manual. Practice (and practice some more) abstracting pertinent information from provider’s documentation and assign the correct codes in the right sequence. Doing this over and over is what will help you learn and code quicker. I hope this helps.

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