What’s The Main Difference Between ICD-9 and ICD-10?

Touseef Riaz

June 3, 2022

What is ICD-9 code for diabetes

The International Classification of Diseases (ICD) is an internationally used and recognized coding tool. It provides crucial knowledge and has several uses around the world. The ICD coding system classifies various conditions, diseases, injuries, and causes of death. The International Classification of Diseases (ICD) is published by the World Health Organisation (WHO). ICD 9 is the 9th revision of the ICD coding system; however, both ICD-10-CM & ICD-10-PCS came into effect on 1st October 2015. There are various differences between ICD 9 and ICD 10 revisions of the ICD coding system.

difference between icd 9 and icd 10

ICD 9 vs ICD 10: What are ICD 9 and CPT coding?

The International Classification of Diseases (ICD) codes and CPT codes are one of the most commonly used coding systems. ICD 9 is the 9th revision of ICD coding assigned to a patient’s diagnosis. This coding system helps the insurance payers, healthcare providers, and patients to understand the condition being treated. For instance, the ICD 9 code for diabetes is 250.00. It is used to report Diabetes mellitus without mention of complication, type II or unspecified type, not stated as uncontrolled. However, this code has been a non-billable code since 1st October 2015.

ICD 9 consists of

  • A tabular list containing a numerical list of disease code numbers in a tabular form
  • An alphabetical index to disease entries
  • A surgical, diagnostic, and therapeutic procedures classification system (both tabular list and alphabetic index).

On the other hand, Current Procedural Terminology (CPT) codes are used to report the healthcare procedures and services performed by the physician. It includes the treatment as well as the diagnostic services. 

ICD 10 Codes:

ICD 10 coding system comprises two medical code sets:


  • International Classification of Diseases, Tenth Revision, Clinical Modification


  • International Classification of Diseases, Tenth Revision, Procedure Coding System

There is a significant difference between the two types of ICD 10 codes:

  • ICD-10-CM — diagnosis code set used for all healthcare settings
  • ICD-10-PCS — procedure code set used only in hospital inpatient settings 

ICD 9 Vs. ICD 10 coding system:

Note that any challenges that were faced with ICD 9 have been addressed with ICD 10 codes. One of the major challenges involved was the lack of specificity with ICD 9 codes. Along with this, adding new codes to address this challenge was also an issue as some chapters were full. However, ICD 10 codes extended the length of characters in the code – expanding the number of codes. And with this increase in the number of codes, the capacity of chapters also increased. The table below consists of major differences among ICD-9-CM & ICD-10-CM codes.

Factors ICD 9 CM ICD 10 CM
No. of codes 13,000 Over 70,000
No. of chapters 17 chapters 22 chapters (order is different than ICD-9-CM)
Supplemental Classification “V” & “E” separate codes; Supplemental Classification for Health Encounters and Injuries/Poisonings Incorporated into the main classification of codes
Reassignment To appropriate body system E.g., Gout/Endocrine Reassigned to the most appropriate chapter

E.g., Gout/Musculoskeletal

Classification of Injuries By type By site and then by type
Post-op complications Separate section Moved to chapter with procedure-specific body system
Character length Three to five Three to seven (Alphanumeric)
4th & 5th character Some codes require the 4th or 5th digit. Full code titles, no 4th and 5th digits

In some chapters: The addition of 6th character

For injuries and external causes of injury: Addition of code extensions via 7th character

 Addition of a placeholder (x)

Greater specificity and laterality (right and left)

Aetiology or manifestations Coded separately Codes combined


The difference in the structure of ICD 9 & ICD 10 codes:

When it comes to the structure of ICD 9 vs ICD 10, they are quite different. ICD-10 codes are alphanumeric; however, ICD 9 codes aren’t. Not only this, but the length of the codes also differs between the two, i.eThere are more characters in ICD 10 codes.

Following are some of the key structural differences between ICD 9 and ICD 10 codes:

The number of digits/characters used:

ICD 10 codes contain a greater number of digits or characters than that of ICD 9. The 9th revision of ICD codes contains 3 to 5 digits/characters (V or E). However, ICD 10 codes contain 3 to 7 characters (alphanumeric). This increase in characters creates and adds more specificity to the ICD codes. ICD 10 codes cover all the diseases and conditions that aren’t covered in ICD 9. The expandability of ICD 10 allows higher specificity so that anatomic site, disease aetiology, and severity can be identified.

For instance:

The ICD-10-CM code for subluxation and dislocation of wrist and hand joints is S63.0. This code is further categorised into the following:

  • S63.0 Subluxation and dislocation of wrist and hand joints
  •  S63.00 Unspecified subluxation and dislocation of wrist and hand
  •  S63.001 Unspecified subluxation of right wrist and hand
  •  S63.001A …… initial encounter
  •  S63.001D …… subsequent encounter
  •  S63.001S …… sequela

 First character:

ICD 9 code starts with either a digit or an alpha (E & V) character (for supplemental classification). However, ICD 10 codes start with an alpha character.

What is an example of ICD 9 CM code and ICD 10 CM code?

V01: Contact with or exposure to communicable diseases – Non-billable code

V01.0: Contact with or exposure to cholera – Billable code

H60.1 Cellulitis of external ear

H60.10 Cellulitis of the external ear, unspecified ear


Diabetes mellitus without mention of complication, type II or unspecified type, not stated as uncontrolled


Type 2 diabetes mellitus without complications


E805 Hit by rolling stock Specific code 

E805.0 Railway employee hit by rolling stock


R00 Abnormalities of heartbeat

R00.0 Tachycardia, unspecified


Second character:

There is no change when it comes to the second digit of ICD 9 and ICD 10 codes. The second character of both revisions is numeric.

Third and other characters:

ICD 9 codes (three to five) are mostly numeric (exception: V & E characters). However, for ICD 10, the third to seventh characters can be either digits or alphabets.

For instance:

ICD-9 Code:

001.0 Cholera due to Vibrio cholerae
241.0  Nontoxic uninodular goiter
E882 Accidental fall from or out of the building or other structure

ICD-10 Code:

F01.51 Vascular dementia with behavioral disturbance
S62.001B Unspecified fracture of the navicular [scaphoid] bone of the right wrist, initial encounter for open fracture

Other differences among ICD 9 vs ICD 10:

Adding new codes:

The ability to add new codes in ICD 9 was limited and one of the major reasons behind the revision to ICD 10. The 10th revision of ICD codes provides a higher level of specificity and detail and flexibility, making it easier to add newly discovered diseases. ICD 9 coding system contained approx. 13,000 codes however, ICD 10 contains over 70,000 codes. Moreover, new codes can also be added to ICD 10 codes. 

Level of specificity:

Higher specificity in ICD 9 vs ICD 10 leads to lesser claim denials, increased accuracy, and improved patient safety. ICD-10 codes provide more specificity than the ICD 9 codes. According to many, this increased specificity also leads to;

  • More detailed diagnoses
  • Lesser requests for documentation to support the diagnosis
  • And lesser claim denials due to lack of medical necessity.

ICD 10 codes can:

  • Measure the efficacy and safety of patient care
  • Assess healthcare expenses and costs
  • Avoid any coding abuse and errors
  • Investigating coding abuse or errors
  • Provider’s performance can also be determined and improved
  • Ability to expand

Combination codes:

Combination codes comprise more than one characteristic of the diagnosis in a single code. They can also be used to report more than two diagnoses. The use of combination codes is allowed in ICD 10; however, ICD 9 doesn’t support the use of combination codes. For instance, the association of diabetic neuropathy with diabetes mellitus type 2 can be coded using a single ICD 10 code, i.e., E11. 40.

Codes for modern technology:

ICD 9 codes don’t emphasize modern technology devices and equipment. And with its expansion limits, new codes couldn’t be added, making it difficult to report and accommodate new technology and procedures. However, new codes can be added to ICD 10 codes, making it easier to keep up with the new technology and procedures.

Key changes in ICD-10 codes:

ICD-10 codes come with several benefits over ICD 9 codes. Some of the key changes include

  • The increased number of codes.
  • And the use of alphabets as well as numbers, therefore, increases the specificity of the code.
  • Code laterality is included in ICD 10 codes (5th and 6th characters), meaning the code indicates that the condition occurred at the left, right, or was bilateral.
  • High level of detail aiding physicians, providers, and payers with
  • Appropriate reimbursement rates
  • Service and resource utilization can be monitored effectively.
  • Offers increased classification, including the risk factors that may be encountered in the primary care setting.
  • Since the last update of ICD 9, diagnoses discovered since then are included in ICD 10.
  • New grouping now:
  • By site
  • Then by the type of the wound.
  • Updated terminology and codes that are consistent with present clinical practice as well as new technology advancements.
  • Offers combination codes
  • ICD 10 also offers expandability, i.e., the ability to add new codes and procedures to keep up with new technology and illnesses.

Advantages of ICD 10 codes:

  • Increased specificity in codes has allowed healthcare providers to accurately report the procedures and services performed.
  • Reduced fraudulent and exaggerated medical claims. Detailed and increased specificity of the codes results in higher reimbursements for providers.
  • Along with higher reimbursements, ICD 10 increases the quality of patient care and improves healthcare functions.
  • With more specificity and detail, providers can monitor their services and outcomes and measure their performance more effectively.
  • Accurate ICD 10 coding requires detailed and accurate documentation, which is why the quality of documentation eventually improves.

Frequently Asked Questions (FAQs)

1. What is ICD 9 & ICD 10 in medical coding?

The International Classification of Diseases (ICD) is one of the most commonly used coding systems. This coding system provides a method of reporting diagnoses and classifying diseases, causes of death, and injuries. ICD 9 is the 9th revision of ICD coding, whereas ICD 10 is the 10th revision of ICD coding.

2. What are common ICD 9 coding errors?

There were various challenges faced in using ICD 9 coding with lesser space to add new codes and the lack of specificity on top of all. ICD-9-CM codes didn’t provide enough information and specificity related to the disease and condition of the patient. 

3. What are common ICD 10 coding errors?

Errors in medical coding results in late payments and lost revenues. Some of the most common coding errors in ICD 10 coding include:

  • Use of outdated codes
  • Using the diagnosis code but forgetting the procedure code
  • Using incorrect code; wrong number, or alphabet
  • Leaving out laterality and specificity

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