2027 ICD-10-CM Diagnosis Code S00.521DBlister (nonthermal) of lip, subsequent encounter
S00.521D is a billable ICD-10-CM diagnosis code for blister (nonthermal) of lip, subsequent encounter. The 7th character D marks it as a subsequent encounter code, used during routine care in the healing or recovery phase. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 949 through 950. The code is exempt from POA reporting. Coders also document this condition as blister of face with infection. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Superficial injury; contusion, subsequent encounter.
Code Identity
Code Classification
Present on Admission (POA)Billing
S00.521D is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Injuries to the head (S00-S09).
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Blister of face with infection
- Blister of face without infection
- Blister of lip
- Blister of lip with infection
- Blister of lip without infection
- Superficial injury of lip
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Superficial injury of head (S00). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to S00.521D: its own notes plus those printed at S00, block S00-S09, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- injuries of ear
- injuries of eye
- injuries of face [any part]
- injuries of gum
- injuries of jaw
- injuries of oral cavity
- injuries of palate
- injuries of periocular area
- injuries of scalp
- injuries of temporomandibular joint area
- injuries of tongue
- injuries of tooth
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- burns and corrosions (T20-T32)
- effects of foreign body in ear (T16)
- effects of foreign body in larynx (T17.3)
- effects of foreign body in mouth NOS (T18.0)
- effects of foreign body in nose (T17.0-T17.1)
- effects of foreign body in pharynx (T17.2)
- effects of foreign body on external eye (T15.-)
- frostbite (T33-T34)
- insect bite or sting, venomous (T63.4)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify any retained foreign body, if applicable (Z18.-)
Code Also
A second code may be needed to fully describe the condition; the note gives no sequencing direction.
- for any associated infection
Notes
General instructions on how these codes are used.
- Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
- The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.
7th Character
Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.
- The appropriate 7th character is to be added to each code from category S00
- Ainitial encounter
- Dsubsequent encounter this code
- Ssequela
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Blisters
Blisters are fluid-filled sacs on the outer layer of your skin. They form because of rubbing, heat, or diseases of the skin. They are most common on your hands and feet.
The full article covers:
- What are blisters?
- What causes blisters?
- What are the treatments for blisters?
- Can blisters be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert S00.521D to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About S00.521DOverview
What is the ICD-10 code for blister (nonthermal) of lip, subsequent encounter?
The ICD-10-CM code for blister (nonthermal) of lip, subsequent encounter is S00.521D (sometimes written as S00521D). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is S00.521D (Blister (nonthermal) of lip) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report blister (nonthermal) of lip, subsequent encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character D in S00.521D mean?
The final character D marks a subsequent encounter: use it for routine care while the blister (nonthermal) of lip is healing, after active treatment has ended.
What MS-DRG does S00.521D group to?
When blister (nonthermal) of lip, subsequent encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 950, 949, with relative weights from 0.7661 to 1.1231 depending on complications. Higher weights mean higher Medicare reimbursement.
Is S00.521D exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for blister (nonthermal) of lip, subsequent encounter on inpatient claims. The code appears in the Injuries to the head (S00-S09) range of the CMS exempt list.
