ICD-10 Code E07.81 – Sick-euthyroid syndrome (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code E07.81 – Sick-euthyroid syndrome
What it is
Sick-euthyroid syndrome, also called nonthyroidal illness syndrome, describes abnormal thyroid function tests during another acute or chronic illness without primary thyroid disease. The thyroid gland is usually not the main problem.
Clinical signs
Clinical features vary; refer to documentation. You may see low T3, sometimes low T4, and thyroid-stimulating hormone that is not appropriately elevated for the illness context.
When to use this code
Use this code when the provider documents sick-euthyroid syndrome, euthyroid sick syndrome, or nonthyroidal illness syndrome. It fits cases where thyroid lab abnormalities are attributed to systemic illness rather than intrinsic thyroid dysfunction. Check the note for the exact diagnosis.
Do not use for
Do not use it for confirmed hypothyroidism, hyperthyroidism, or other primary thyroid disorders. If the record only shows abnormal thyroid tests without a documented syndrome, check documentation.
Coding tip
Code E07.81 only when the clinician links the thyroid test pattern to the patient’s illness, not just to an isolated lab result.