ICD-10 Code A36.9 – Diphtheria, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A36.9 – Diphtheria, unspecified
What it is
A36.9 identifies diphtheria when the site or type is not documented. Use it for confirmed diphtheria infections when the record does not specify a more precise form.
Clinical signs
Clinical features vary; refer to documentation. Classic diphtheria may include sore throat, fever, and a gray pharyngeal membrane, but you should code only what is documented in the chart.
When to use this code
Use this code when the provider documents diphtheria without naming the throat, nasal, cutaneous, or other specific site. It also fits cases where the record confirms diphtheria but leaves the presentation unspecified.
Do not assume a more detailed code from symptoms alone. If the note is incomplete, you should code the unspecified diagnosis and query when clarification is needed.
Do not use for
Do not use A36.9 for suspected diphtheria, carrier status, or a different bacterial throat infection. Check documentation if the organism or anatomic site is identified elsewhere.
Coding tip
Assign the most specific diphtheria code available; use A36.9 only when the record truly lacks site or type detail.