International Classification of Diseases (ICD) codes are found on patient paperwork, including hospital records, medical charts, visit summaries, and bills. These codes ensure that you get proper treatment and are charged correctly for any medical services you receive.
The 10th version of the code, in use since 2015, is called the ICD-10 and contains more than 70,000 disease codes.1 The ICD is maintained by the World Health Organization (WHO) and distributed in countries across the globe.
How ICD Codes Are Used.
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.
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.
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.
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.2
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.
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.3
ICD codes are also used in clinical trials to recruit and track subjects and are sometimes, though not always, included on death certificates.
ICD Code Updates.
The 2015 revision to the ICD involved a number of changes. As a result, ICD-10 codes are approached differently from their ICD-9 counterparts.
While phased out in 2015, ICD-9 codes still appear on older documents. Most ICD-9 codes are three digits to the left of a decimal point and one or two digits to the right of one. For example:
250.0 is diabetes with no complications.
530.81 is gastroesophageal reflux disease (GERD).
079.99 is a virus.
Some ICD-9 codes have a “V” or “E” in front of them. A “V” code is used for health services (usually preventive) that don’t require a diagnosis. An “E” code describes an environmental cause of a health problem, such as an injury or poisoning.
The ICD-10 update completely overhauled the coding system. The new codes—more than 14,000 in all—are broken down into chapters and subchapters and include a letter plus two digits to the left of the decimal point, then one digit to the right.
The new system allows for a more specific diagnosis. For example:
E10.9 is type 1 diabetes and E11.9 is type 2 diabetes.
K21.9 is GERD.
B97.89 is a virus as a cause of disease classified elsewhere.
The letters group diseases together and describe a specific condition, organ system, or characteristic of a condition. This may cause initial confusion because “E” no longer stands for an environmental cause but rather endocrine disorders.4
ICD-10 Diagnostic Codes From A to Z
A: Infectious and parasitic diseases
B: Infectious and parasitic diseases
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
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
How ICD Codes Work.
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 0.5
Where to Find ICD Codes
When you leave a healthcare provider’s appointment, therapy appointment, or hospital, you are given a visit summary that should include different codes. Your ICD codes are listed under “diagnosis” or “Dx,” while other codes are typically CPT codes for services rendered.
When you receive an explanation of benefits (EOB) from your insurance company, Medicare, or another payer, it also contains ICD codes.
If a claim is being disputed or is not being paid, it may be because the ICD code does not align with the CPT code. If this occurs, speak with someone in the billing department of your healthcare provider.
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 searchable database of the current ICD-10 codes.
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.