T78.2XXA — Anaphylactic shock, unspecified, initial encounter
T78.2XXA is a billable, specific ICD-10-CM code for anaphylactic shock, unspecified, initial encounter. It is valid for submission on a claim.
7th character "A" — initial encounter
The appropriate 7th character is to be added to each code from category T78
- A
- initial encounter
- D
- subsequent encounter
- S
- sequela
Excludes1 — never code together
These conditions cannot occur together. Billing both on the same encounter is a denial.
Inclusion terms
Alternative wordings a physician may use in the chart for this same code.
- Allergic shock
- Anaphylactic reaction
- Anaphylaxis
Excludes1 inherited from the categories above T78.2XXA
These are not written on T78.2XXA, but they bind it: a note on a category applies to every code beneath it. Billing T78.2XXA with anything listed here is a denial.
Excludes2 inherited from the categories above T78.2XXA
Also inherited, and the opposite of Excludes1: these conditions are not part of T78.2XXA, but a patient can have both, so you may code both.
Other codes that can never be billed with T78.2XXA
These codes carry an Excludes1 note pointing at T78.2XXA. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading T78.2XXA alone.
- T75Other and unspecified effects of other external causes
Risk adjustment
T78.2XXA 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
T78.2XXA is named in 8 Medicare coverage policies — 8 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.
- A56612Billing and Coding: CT of the Head
- A56730Billing and Coding: Respiratory Therapy and Oximetry Services
- A56844Billing and Coding: RAST Type Tests
- A57043Billing and Coding: RAST Type Tests
Code history
T78.2XXA has not changed since FY2024 — no addition, revision or deletion across the three most recent ICD-10-CM releases.
Related codes at this level
Codes that share T78.2. If T78.2XXA is not quite right, the correct code is usually one of these.
Questions about T78.2XXA
- Is T78.2XXA a billable ICD-10-CM code?
- Yes. T78.2XXA is a billable, specific ICD-10-CM code and is valid for submission on a claim.
- Where does T78.2XXA sit in the tabular list?
- Injury, poisoning and certain other consequences of external causes (S00-T88), in the block Other and unspecified effects of external causes (T66-T78).
- What cannot be coded together with T78.2XXA?
- T78.2XXA carries Excludes1 notes, which means the conditions they list can never be coded together with it on the same encounter. Some are written on the categories above T78.2XXA (T78.2) and apply to it just the same.