ICD 10 Codes and How to Look Them Up

The right code ensures you're correctly treated and billed

International Classification of Diseases (ICD) codes are a set of designations used by healthcare staff to communicate diseases, symptoms, abnormal findings, and other elements of a patient's diagnosis in a way that is universally accepted by those in the medical and insurance fields. The tenth and most recent edition is known as ICD-10.

ICD-10 codes are passed to insurance companies to establish the medical necessity of the services a provider is asking to be paid for. There are more than 70,000 of them, and their highly specific definitions are understood by all who use them.

While ICD-10 codes often appear on patient paperwork and bills, they don't always. Looking up these codes can become quite important if you're trying to sort out a medical pre-approval or billing issue with your insurance provider. An incorrect code can mean that coverage of practitioner visits and treatments gets denied.

This article explains how medical professionals use ICD codes, why they matter to you, and how you can find an ICD-10 when you need it.

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How to Look Up ICD-10 Codes

You may want to look up an ICD code because:

  • Your insurance claim is being disputed
  • Your insurance claim has not been paid
  • You have submitted for pre-approval for a certain treatment or specialist visit and were denied

This sometimes happens when an ICD code does not align with a CPT code, which is similar designation that identifies the services rendered or being requested.

You may be able to find ICD-10 codes for a recent visit by checking out the summary given to you by your healthcare provider or hospital. ICD codes should be listed under "diagnosis" or "Dx."

Explanation of benefits (EOB) statements from your insurance company, Medicare, or another payer may also contain ICD codes.

If you need to look up the ICD code for a particular diagnosis or confirm what an ICD code stands for, visit the Centers for Disease Control and Prevention (CDC) website to use their free searchable database of current ICD-10 codes.

Having ICD-10 codes on-hand—both the correct ones for your situation and those that were filed in your case, if different—can help you have a more productive conversation with your provider, their billing department, and your insurance company.

How ICD Codes Are Used

ICD codes are used in billing, treatments, and statistics collection. Having the right code is important to ensure that standardized treatment for a medical issue is delivered and that medical expenses are reimbursed.

In the United States, ICD codes are overseen by the Centers for Medicare and Medicaid Services (CMS) and the National Center for Health Statistics (NCHS). 

The ICD receives annual updates in between revisions, which is sometimes reflected in the code title. For example, the 2020 updated version was the ICD-10-CM. The ICD-11 was approved by the WHO in 2019 so it can go into effect in 2022.

The ICD is maintained by the World Health Organization (WHO) and used across the globe, with some country-specific modifications.

Insurance Reimbursement

When your healthcare provider submits a bill to an insurance company for reimbursement, each service is described by a common procedural technology (CPT) code. It is matched to an ICD code. If the two codes don't align correctly with each other, the company may deny payment.

In other words, if the service isn't one that would typically be provided for someone with that diagnosis, an insurance company will not pay.

For example, your healthcare provider should not submit a bill for an X-ray if you come in complaining of a rash since imaging is not indicated for that concern.

Disease Management

An ICD code is assigned to every disease. If you have a chronic illness, such as diabetes or heart disease, your ICD code will typically follow your medical records.

In a hospital setting, this can be lifesaving. But for patients with chronic conditions who come to the hospital for an unrelated issue, this can cause frustration.

When you meet a new healthcare provider, they may ask questions about the chronic illness first instead of focusing on your reason for being in the hospital. However, while a condition may seem unrelated to you, there may be a connection known only to the physician.

This process makes sense when you consider that about 80% of "older adults" have at least one chronic health condition while 50% have two or more.

Still, this reality sometimes results in a provider ordering unnecessary tests and treatments that are indicated for the chronic condition rather than focusing on the concern that caused you to seek treatment.

Other Uses

ICD codes are used globally to track health statistics and causes of death. This is helpful for gathering data on chronic illnesses as well as new ones. For example, a new code was added to the ICD-10 in 2020 to track vaping-related illnesses.

ICD codes are also used in clinical trials to recruit and track subjects and are sometimes, though not always, included on death certificates.

Elements of ICD-10 Codes

The ICD is maintained by the World Health Organization (WHO) and used across the globe, with some country-specific modifications.

The ICD-10 update in 2015 completely overhauled the coding system. The new codes are broken down into chapters and subchapters. They include a letter plus two digits to the left of the decimal point, then one or two digits to the right.

The letters group diseases together and describe a specific condition, organ system, or characteristic of a condition. The numbers further refine that definition.

For example, E10.9 stands for type 1 diabetes and E11.9 is type 2 diabetes.

The letter is determined by the nature of the diagnosis:

  • A: Infectious and parasitic diseases
  • B: Infectious and parasitic diseases
  • C: Cancer
  • D: Neoplasms, blood, and blood-forming organs
  • E: Endocrine, nutritional, or metabolic
  • F: Mental and behavioral disorders
  • G: Nervous system
  • H: Eyes, ears, nose, and throat
  • I: Circulatory system
  • J: Respiratory system
  • K: Digestive system
  • L: Skin
  • M: Musculoskeletal system
  • N: Genitourinary system
  • O: Pregnancy and childbirth
  • P: Perinatal conditions
  • Q: Congenital and chromosomal abnormalities
  • R: Abnormal clinical and lab findings
  • S: Injury, poisoning, and other external causes
  • T: Injury, poisoning, and other external causes
  • U: Used for emergency designation
  • V: External causes of morbidity
  • W: External causes of morbidity
  • X: External causes of morbidity
  • Y: External causes of morbidity
  • Z: Factors influencing health status and contact with health services

Updating ICD-10 Codes

In 2022, the ICD codes will change again with the addition of two numbers—one that precedes the letter and one that comes at the end. For example, X98.6 (ICD-10 code) will become 0X98.60.

The updated code also does not use letters "I" or "O" to avoid confusion with 1 and 0.

This new edition will be called ICD-11.


The International Classification of Diseases (ICD) is a tool that assigns codes—a kind of medical shorthand—for diseases, signs and symptoms, abnormal findings, circumstances, and external causes of diseases or injury. Insurance companies expect the codes to be consistent between a condition and the treatment rendered. Otherwise, they may balk at paying. This is reason enough to learn how to look them up for yourself.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. International classification of diseases, tenth revision, clinical modification (ICD-10-CM).

  2. Centers for Disease Control and Prevention. Depression is not a normal part of growing older.

  3. Centers for Disease Control and Prevention. New ICD-10-CM code for vaping-related disorder to be implemented April 1, 2020.

  4. Cartwright DJ. ICD-9-CM to ICD-10-CM codes: What? why? how? Adv Wound Care (New Rochelle). 2013;2(10):588–592. doi:10.1089/wound.2013.0478

  5. World Health Organization. ICD-11 reference guide.

By Trisha Torrey
 Trisha Torrey is a patient empowerment and advocacy consultant. She has written several books about patient advocacy and how to best navigate the healthcare system.