Is R21 a billable ICD-10-CM code?

Yes. R21 is a billable, specific ICD-10-CM code and is valid for submission on a claim.

Where does R21 sit in the tabular list?

Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99), in the block Symptoms and signs involving the skin and subcutaneous tissue (R20-R23).

What cannot be coded together with R21?

R21 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.

R21

R21 — Rash and other nonspecific skin eruption

Billable / specific codeICD-10-CM

R21 is a billable, specific ICD-10-CM code for rash and other nonspecific skin eruption. It is valid for submission on a claim.

Excludes1 — never code together

These conditions cannot occur together. Billing both on the same encounter is a denial.

specified type of rash- code to condition
vesicular eruption (R23.8)

Includes

Conditions this code covers.

rash NOS

Risk adjustment

R21 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.

Medicare coverage

R21 is named in 17 Medicare coverage policies — 17 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.

A55326Billing and Coding: Zika Virus Testing by PCR and ELISA Methods
A56587Billing and Coding: Cosmetic and Reconstructive Surgery
A56658Billing and Coding: Cosmetic and Reconstructive Surgery
A56837Billing and Coding: Reduction Mammaplasty

How R21 is indexed

Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to R21.

Rash(toxic)
Eruption›skin(nonspecific)
Rash›rose
Rose›rash

Questions about R21

Is R21 a billable ICD-10-CM code?: Yes. R21 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
Where does R21 sit in the tabular list?: Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99), in the block Symptoms and signs involving the skin and subcutaneous tissue (R20-R23).
What cannot be coded together with R21?: R21 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.