ICD and CPT Codes: The Language of Healthcare Billing

Whether you’re billing for health care services through insurance or using a superbill, there are several key pieces of information that the payer will need in order to understand what you’re billing for and determine whether (and how much) to pay for it. Because larger payers receive millions of claims each year, this key information is usually provided in codes for efficiency. Two of the most important coding systems to understand in billing are ICD codes and CPT codes. 

Here we’ll go into more detail about these key billing codes and what they communicate, why they’re so important, and how to find the right code when you’re not sure.

What’s the Difference Between ICD and CPT Codes?

The difference between ICD and CPT codes is what they describe. CPT codes refer to the treatment being given, while ICD codes refer to the problem that the treatment is aiming to resolve. The two work hand-in-hand to quickly provide payors specific information about what service was performed (the CPT code) and why (the ICD code).

What’s the Importance of CPT Codes?

CPT codes—formally, Current Procedural Terminology codes— are the codes used to describe clinical procedures and activities in health care. In other words, they refer to what the health care provider did during an interaction with or on behalf of a client or patient. CPT codes are developed by the American Medical Association, and used among federal government programs like Medicare and Medicaid, and private payers like insurance companies. Simply put, they’re the standard procedural language used across health care in the US. New CPT codes are released several times each year, to keep up with new developments in health care services.

Most health care providers primarily use the five-digit CPT codes considered Category I. These are the codes most often used for billing purposes, as they identify specific, well-established procedures. With some meaningful exceptions, US insurers typically must pay for Category I procedures performed by a qualified health care professional when they are medically necessary to treat a client or patient’s condition. Category II codes are used to gather information about quality of care, while Category III codes are used for newer procedures and technologies. 

What’s the Importance of ICD Codes?

ICD codes, or International Classification of Disease codes, are used to describe the client’s diagnosis. In other words, they refer to the condition that’s being treated. ICD codes are developed by WHO, the World Health Organization, and used around the world. In addition to being used in the process of health care billing, ICD codes are also used to identify health and disease trends across countries. Simply put, they’re the standard diagnostic language used by health care providers, payers, researchers, and public health officials around the world. 

Updates to ICD codes are published on an irregular basis, with minor updates published every one to four years. Entirely new versions of the ICD, which typically include more significant changes in coding and structure, are published far less often. The current version, ICD-10, entered common use in 1994. The ICD-11 was formally adopted in May 2019 and takes effect January 1, 2022.

How to Look Up an ICD Code for Your Diagnosis

ICD codes are available online in a variety of formats. You can search the official ICD-10 online, or browse the official ICD-11 online. There are also a number of websites that index ICD codes in different ways, aiming to make it easier to find the code you need. 

If you’re a mental health care provider and looking to determine an ICD code on the basis of a DSM diagnosis, there are a number of online “crosswalks” you can use to find the right ICD code. Naturally, it’s important to review the language of that code on the official ICD site, as the diagnostic indicators and requirements of the DSM-5 don’t always line up perfectly with the diagnostic indicators and requirements in the ICD.

How to Look Up a CPT Code for Your Procedure

You can order the most current CPT manual in book form, but given how often codes are updated, you would need to regularly order newer versions. It’ll likely be easier to look up codes within your practice management software, or somewhere online. Many professional associations of health care providers publish lists of the most common CPT codes for their respective groups. For social workers, this list from NASW is an example of commonly used CPT codes within that profession. When there are new codes issued or other key developments, the AMA website has a subsite specific to CPT, with a number of resources freely available to ensure your coding knowledge is current.

Although it may seem overwhelming with the number of codes you might need to use, once you have a basic understanding of them,  you’ll have the foundation you need to start billing insurance in your private practice. Now you’ll have the opportunity to open up care to more clients, grow your practice—and your impact. 

Note: CPT is a registered trademark of the American Medical Association.


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