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E03.9 Hypothyroidism ICD 10: Diagnosis

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Unspecified Hypothyroidism ICD 10 code E03.9. E03.9 is a billable ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes, and it remains valid in the 2027 edition that took effect on October 1, 2026.

ICD-10 is the World Health Organization's International Classification of Diseases, 10th revision. ICD-10-CM (Clinical Modification) is the version used in the United States to code diagnoses. Physicians and other health care providers use these codes to record a diagnosis; the code itself does not diagnose the disease. ICD-10 replaced ICD-9 because it allows more detail and specificity.

For Hypothyroidism, unspecified, E03.9 is the code used when the type of hypothyroidism is not specified. Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone. Causes include autoimmune thyroiditis (Hashimoto thyroiditis), thyroid surgery, radioactive iodine treatment, radiation to the neck, certain medicines, and thyroid problems present from birth.

MedlinePlus lists common symptoms such as feeling cold, weight gain, constipation, fatigue, dry skin, brittle hair or nails, joint or muscle pain, depression, and heavier or irregular periods. In infants and children, untreated hypothyroidism can slow growth and development.

In the United States, the most common cause of hypothyroidism is Hashimoto thyroiditis, an autoimmune disorder in which the immune system gradually damages the thyroid. Many other causes exist. Approximate synonyms that map to the E03 codes include:

  • Hypothyroidism in pregnancy
  • Hypothyroidism in childbirth
  • Hypothyroidism (low thyroid)
  • Hypothyroidism postpartum
  • Acquired hypothyroidism
  • Hypothyroidism (low thyroid), acquired
  • Cerebral degeneration due to hypothyroidism
  • Cerebral degeneration in hypothyroidism
  • Hypothyroidism
  • Hypothyroid (low level of thyroid hormone) in childbirth
  • Hypothyroid (low thyroid) in pregnancy
  • Myxedema
  • Subclinical hypothyroidism
  • Postpartum (after childbirth) hypothyroidism
  • BILLABLE: Yes E03.9 is a billable hypothyroidism ICD 10 code and is applicable to Myxedema NOS

Note that autoimmune thyroiditis has its own code, E06.3, not E03.9. The following terms are coded to E06.3:

  • Fibrous autoimmune thyroiditis
  • Hashimoto thyroiditis
  • Thyroiditis (inflammation of the thyroid), Hashimoto
  • Thyroiditis, autoimmune
  • Thyroiditis, fibrous autoimmune
  • Hashimoto’s thyroiditis
  • Hashitoxicosis (transient)
  • Lymphocytic thyroiditis
  • Lymphadenoid goiter
  • Struma lymphomatosa

Hypothyroidism Icd 10 Code Tree

E03.9 is a specific ICD-10-CM code for hypothyroidism, unspecified. Other codes are

  • E00-E07 – Disorders of the thyroid gland
  • E03 – Other hypothyroidism
  • Excludes1: iodine-deficiency related hypothyroidism (E00-E02) and postprocedural hypothyroidism (E89.0)
  • E03.0 – Congenital hypothyroidism with diffuse goiter

Exclude: Transitory Congenital Goiter with Normal Function

  • E03.1 – Congenital hypothyroidism without goiter
  • E03.2 – Hypothyroidism due to medicaments and other exogenous substances
  • E03.3 – Postinfectious hypothyroidism
  • E03.4 – Atrophy of thyroid (acquired)

Exclude: Congenital Atrophy of Thyroid

  • E03.5 – Myxedema coma
  • E03.8 – Other specified hypothyroidism
  • E03.9 Hypothyroidism, unspecified

Always confirm the final code against the current ICD-10-CM code set, and see a clinician for diagnosis and treatment of thyroid problems.

HP Thoughts: Headaches also have their own diagnosis codes. View them here: Headache ICD 10.

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