T33.821A (Superficial frostbite of right foot, initial encounter) compared with T33.821S (Superficial frostbite of right foot, sequela), from the official CMS tabular data. T33.821A and T33.821S code the same injury at a different phase of treatment.
Same underlying diagnosis, different encounter phase.
The 7th character records the phase of care for the encounter being coded, so a single encounter takes one of these characters, not several. Review whether both phases belong on the same episode of care.
Source: ICD-10-CM Official Guidelines, Section I.C.19.a
Same injury, other encounter phase. T33.821A and T33.821S code the same injury at a different phase of treatment, set by the 7th character.
The 7th character records the type of care given at the encounter being coded (ICD-10-CM Official Guidelines, Section I.C.19.a), so one encounter takes one of these, not both.
| T33.821ASuperficial frostbite of right foot, initial encounter | T33.821SSuperficial frostbite of right foot, sequela | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) |
| Definition | Superficial frostbite of right foot, initial encounter is a billable ICD-10-CM diagnosis code (T33.821A). | Superficial frostbite of right foot, sequela is a billable ICD-10-CM diagnosis code (T33.821S). |
| 7th character | The appropriate 7th character is to be added to each code from category T33 | The appropriate 7th character is to be added to each code from category T33 |
| Includes | frostbite with partial thickness skin loss | frostbite with partial thickness skin loss |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources