ICD-10 Code E03.3 – Postinfectious Hypothyroidism (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code E03.3 – Postinfectious hypothyroidism
What it is
E03.3 identifies hypothyroidism that develops after an infection. Use it when the record shows thyroid underactivity linked to a prior infectious process.
Clinical signs
Clinical features vary; refer to documentation. Common hypothyroid findings may include fatigue, cold intolerance, weight gain, constipation, and slowed thinking, but the postinfectious cause should be documented.
When to use this code
Use E03.3 when the clinician clearly documents postinfectious hypothyroidism or thyroid dysfunction following infection. It is appropriate when the note links the condition to a prior infectious illness rather than to surgery, medication, or autoimmune disease.
If the chart only says hypothyroidism without a cause, do not assume this code. Check documentation for the specific postinfectious relationship before assigning E03.3.
Do not use for
Do not use this code for unspecified hypothyroidism, congenital hypothyroidism, or hypothyroidism caused by thyroid surgery, radiation, or drugs. Check documentation if the etiology is unclear.
Coding tip
Code E03.3 only when the postinfectious cause is explicitly documented; otherwise, select the documented hypothyroidism code.