Hypothyroidism shows up in almost every primary care, endocrinology and internal medicine claim queue. Yet coders still lose money on it every week. One wrong character turns E03.9 into a denial, a Z-code on an active patient triggers an audit, and a secondary hypothyroidism claim bounces between two conflicting codes. This guide fixes that. You get every hypothyroidism ICD 10 code, the rules for choosing between them, and billing tips verified against the FY2027 code set.
TL;DR
- The ICD 10 code for hypothyroidism, unspecified, is E03.9. It is billable and can be the principal diagnosis.
- Acquired hypothyroidism with no stated cause also codes to E03.9. Acquired thyroid atrophy codes to E03.4.
- Secondary, central and tertiary hypothyroidism code to E03.8. Add E23.0 when the provider documents hypopituitarism.
- Congenital hypothyroidism codes to E03.0 (with goiter) or E03.1 (without goiter).
- Hashimoto’s codes to E06.3, post-surgical hypothyroidism to E89.0, and drug-induced hypothyroidism to E03.2 plus a T-code.
- History of hypothyroidism is Z86.39 (resolved cases only). Family history is Z83.49.
- The FY2027 update, effective October 1, 2026, made no changes to category E03.
What Is the ICD 10 Code for Hypothyroidism?
The ICD-10-CM code for hypothyroidism is E03.9, Hypothyroidism, unspecified. This code also covers myxedema NOS. Coders assign it when the provider confirms hypothyroidism but does not document the cause.
E03.9 sits in Chapter 4, Endocrine, nutritional and metabolic diseases (E00–E89). Within that chapter, it falls under Disorders of thyroid gland (E00–E07) and then category E03, Other hypothyroidism.
Category E03 carries two Excludes1 notes. You cannot report E03 codes together with iodine-deficiency hypothyroidism (E00–E02) or postprocedural hypothyroidism (E89.0). Those conditions have their own codes, and the Excludes1 rule blocks dual coding.
You will also see this code written as “E039” or “dx E03.9” in search queries and some EHR exports. These dotless variants all refer to the same ICD-10-CM code for hypothyroidism unspecified. Finally, if you are a patient who found E03.9 on a chart, it simply means your provider confirmed an underactive thyroid without naming a specific cause.
Is E03.9 Billable, and Can It Be a Primary Diagnosis?
Yes. E03.9 is a billable, specific ICD-10-CM code, and you can report it as the principal or first-listed diagnosis when hypothyroidism drives the visit. Payers accept it on both professional and facility claims.
For inpatient claims, E03.9 groups to MS-DRG 643 through 645 (Endocrine disorders with MCC, with CC, or without CC/MCC). On the risk-adjustment side, it maps to RxHCC 44, Thyroid and Parathyroid Disorders, which matters for Medicare Advantage plans.
However, auditors watch unspecified codes closely. When the chart supports a more specific code, such as E06.3 for Hashimoto’s, you should use it instead. Defaulting to E03.9 on every thyroid patient is the most common over-coding pattern in primary care.
Complete List of Hypothyroidism ICD-10 Codes (E03.0–E03.9)
Category E03 contains eight billable codes. Each one describes a different cause or presentation, so review the documentation before you pick one.
| Code | Description | Use when |
|---|---|---|
| E03.0 | Congenital hypothyroidism with diffuse goiter | Present at birth, goiter confirmed on exam or imaging |
| E03.1 | Congenital hypothyroidism without goiter | Present at birth, thyroid normal size, absent or ectopic |
| E03.2 | Hypothyroidism due to medicaments and other exogenous substances | Caused by a drug or external agent |
| E03.3 | Postinfectious hypothyroidism | Follows a documented infection of the thyroid |
| E03.4 | Atrophy of thyroid (acquired) | Provider documents acquired thyroid atrophy |
| E03.5 | Myxedema coma | Life-threatening decompensated hypothyroidism |
| E03.8 | Other specified hypothyroidism | Secondary, central or tertiary hypothyroidism |
| E03.9 | Hypothyroidism, unspecified | Cause not documented |
One quick warning: several online guides list E03.5 as thyroid atrophy. That is wrong. E03.5 is myxedema coma, and E03.4 is atrophy. Always verify against the current Tabular List rather than a third-party summary.
ICD 10 Code for Acquired Hypothyroidism
There is no separate ICD 10 code for acquired hypothyroidism. The Alphabetic Index routes “Hypothyroidism (acquired)” directly to E03.9, so acquired hypothyroidism with no stated cause uses the same unspecified code.
The one exception is acquired thyroid atrophy. When the provider documents that the gland has shrunk and the atrophy was not present at birth, assign E03.4 instead.
The word “acquired” simply tells you the condition developed after birth. It separates the diagnosis from the congenital codes (E03.0 and E03.1), but it does not add specificity on its own. Therefore, before you settle on E03.9, ask the provider whether the cause is autoimmune, surgical or drug-related. Each of those answers moves you to a more specific and more defensible code.
Primary vs Secondary Hypothyroidism ICD-10 Codes
Primary hypothyroidism without a stated cause codes to E03.9. Secondary, central and tertiary hypothyroidism code to E03.8, and you add E23.0 when the provider documents hypopituitarism. The site of failure decides the code.
| Type | Where the failure occurs | Typical labs | ICD-10-CM code |
|---|---|---|---|
| Primary | Thyroid gland | High TSH, low free T4 | E03.9 (or E06.3, E89.0, E03.2 if cause known) |
| Secondary | Pituitary gland | Low or normal TSH, low free T4 | E03.8 (+ E23.0) |
| Tertiary | Hypothalamus | Low or normal TSH, low free T4 | E03.8 |
You will find conflicting advice on secondary hypothyroidism across the web. Some sources send it to E23.0 alone, while others use E03.8 alone. The Tabular List settles this. The inclusion terms under E03.8 specifically list secondary, central and tertiary hypothyroidism, so E03.8 is the code for the thyroid condition itself.
E23.0 describes hypopituitarism, which is the pituitary disorder causing the problem. As a result, when the provider documents both, you report E23.0 for the pituitary failure and E03.8 for the resulting hypothyroidism. Sequence them according to the reason for the encounter.
For primary hypothyroidism, the lab pattern tells the story. A high TSH with a low free T4 confirms the thyroid gland failed on its own. If the provider names the cause, skip E03.9 and code the cause.
Congenital Hypothyroidism ICD-10 (E03.0 vs E03.1 vs P72.2)
Congenital hypothyroidism codes to E03.1 when there is no goiter and E03.0 when a diffuse goiter is present. The National Library of Medicine’s newborn screening guide maps primary congenital hypothyroidism to E03.1, which also carries the inclusion term “Congenital hypothyroidism NOS.” (NLM Newborn Screening Coding and Terminology Guide)
Transient neonatal hypothyroidism is a different condition. It resolves on its own and codes to P72.2, Other transitory neonatal disorders of thyroid function. Codes from Chapter 16 (P00–P96) belong only on the newborn’s record, never the mother’s.
P72 carries an Excludes1 note for E03.0 and E03.1, so you cannot report transient and permanent congenital hypothyroidism together. To support either code, document the newborn screening result, confirmatory TSH and T4 values, and any thyroid imaging.
Related Codes Coders Confuse With E03.9
Many hypothyroidism claims fail because the coder chose E03.9 when a different category applied. The table below covers the scenarios that cause the most rework.
| Scenario | Correct code(s) |
|---|---|
| Hashimoto’s or autoimmune thyroiditis | E06.3 |
| Hypothyroidism after thyroidectomy or radioactive iodine | E89.0 |
| Drug-induced (amiodarone, lithium, checkpoint inhibitors) | E03.2 plus the adverse-effect T-code |
| Iodine-deficiency hypothyroidism | E01.8, or E02 for subclinical iodine-deficiency cases |
| Subclinical hypothyroidism, non-iodine | E03.9 if the provider diagnoses hypothyroidism; R94.6 if only “abnormal TSH” is documented |
| Hypothyroidism in pregnancy | O99.28- first, then E03.9 |
| “Thyroid disorder” with no further detail | E07.9 (not for confirmed hypothyroidism) |
Two of these trip coders constantly. First, E02 applies only to subclinical hypothyroidism caused by iodine deficiency, which is rare in the United States. For the usual mildly elevated TSH with normal free T4, code E03.9 if the provider diagnoses hypothyroidism, or R94.6 if the note only says the test was abnormal.
Second, drug-induced cases need two codes. Report E03.2 for the hypothyroidism, then add the T-code with a fifth or sixth character of 5 for adverse effect in therapeutic use, such as T46.2X5- for amiodarone. The Official Guidelines require the T-code as an additional code, never as the principal diagnosis.
History of Hypothyroidism ICD-10 (Z86.39) and Family History (Z83.49)
A personal history of hypothyroidism codes to Z86.39, and a family history codes to Z83.49. However, a patient who still takes levothyroxine has active hypothyroidism, so you must code E03.9, not Z86.39.
This is the single most common Z-code error on thyroid claims. Z86.39 belongs to Chapter 21, Personal history of other endocrine, nutritional and metabolic disease, and it applies only when the condition has resolved and the patient no longer receives treatment. Because most hypothyroidism is lifelong, Z86.39 rarely fits.
For the typical stable patient on replacement therapy, report E03.9 with Z79.899, Other long term (current) drug therapy. This combination tells the payer the condition is active and managed.
Family history works differently. Z83.49, Family history of other endocrine, nutritional and metabolic diseases, covers a parent or sibling with hypothyroidism or Hashimoto’s. You will sometimes see Z83.1 suggested for thyroid family history. That is incorrect, because Z83.1 covers family history of infectious and parasitic diseases.
Both Z-codes work as additional diagnoses. Z83.49 can also support medical necessity for TSH screening in a patient without symptoms.
Hypothyroidism Coding Decision Flowchart
Use this sequence whenever a hypothyroidism diagnosis lands in your queue.
- Did the provider document a cause? If no, assign E03.9.
- Autoimmune or Hashimoto’s? Assign E06.3.
- Surgery or radioactive iodine? Assign E89.0.
- Medication or external substance? Assign E03.2 plus the T-code.
- Pituitary or hypothalamic failure? Assign E03.8, and add E23.0 for hypopituitarism.
- Present at birth? Assign E03.0 with goiter or E03.1 without.
- Documented acquired atrophy? Assign E03.4.
- Myxedema coma? Assign E03.5.
CPT Codes That Pair With E03.9 and Billing Tips
E03.9 most commonly supports CPT 84443 (TSH), 84439 (free T4), 84436 (total T4), 84480 (T3, total) and 86376 (thyroid peroxidase antibodies). The diagnosis must link to each lab line on the claim.
| CPT code | Test | Medical-necessity note |
|---|---|---|
| 84443 | TSH | Most payers allow routine monitoring; check frequency limits |
| 84439 | Free T4 | Pair with TSH when dose adjustment is documented |
| 84436 | Total T4 | Less common; justify why free T4 was not used |
| 84480 | T3, total | Needs documented clinical reason |
| 86376 | TPO antibodies | Supports work-up for E06.3, usually once |
Four denial triggers account for most thyroid rejections. First, payers reject E03.9 when the chart clearly supports a specific code. Second, repeated TSH testing can exceed frequency limits, so document why the provider rechecked it. Third, Z86.39 on a patient taking levothyroxine signals an inactive condition and voids medical necessity. Fourth, missing diagnosis pointers leave lab lines unlinked.
Your documentation should include five elements: the diagnosis statement, the etiology when known, lab values with dates, the current medication and dose, and the status of the condition. If you bill thyroid labs as a panel, the bundling logic in our CPT Code 80061 lipid panel guide applies the same way.
Worked Coding Examples
Example 1: Stable hypothyroidism on levothyroxine, no cause stated. The provider documents “hypothyroidism, well controlled on levothyroxine 75 mcg.” Report E03.9 and Z79.899. If this is a new patient visit, pair it with the right E/M level from our 99203 CPT code guide.
Example 2: Hashimoto’s thyroiditis with hypothyroidism. Positive TPO antibodies and the provider names Hashimoto’s. Report E06.3 alone. Do not add E03.9, because the Excludes notes and specificity rules make it redundant.
Example 3: Hypothyroidism after total thyroidectomy for papillary cancer. Report E89.0 for the postprocedural hypothyroidism, then Z85.850 for personal history of malignant neoplasm of thyroid. For established follow-up visits, our 99214 CPT code guide covers the E/M requirements.
Example 4: Panhypopituitarism with central hypothyroidism. Report E23.0 for the hypopituitarism and E03.8 for the resulting hypothyroidism. Sequence E23.0 first when the pituitary disease drives the visit.
FY2027 ICD-10-CM Update: What Changed for Hypothyroidism?
Nothing changed. The FY2027 ICD-10-CM update took effect on October 1, 2026, and every code in category E03 remains exactly as it was. CMS confirms the new files apply to encounters and discharges from October 1, 2026 through September 30, 2027. (CMS ICD-10 Codes)
Chapter 4 received only two new codes this cycle, E89.830 and E89.838 for postprocedural hypoglycemia, and neither affects thyroid coding. The FY2027 Official Guidelines for Coding and Reporting also carry no new thyroid-specific instructions. (FY2027 ICD-10-CM Official Guidelines, PDF)
Remember the date-of-service rule. Any visit on or after October 1, 2026 must use the FY2027 set, even if your software has not refreshed yet.
Final Thoughts
Reserve E03.9 for cases where the provider truly did not document a cause, and query the provider whenever the labs or history point to something more specific. Review your thyroid code set every October 1 and April 1, because the annual update and the mid-year guideline revisions can shift the rules. Cure MD Billers will keep this guide current with each cycle.
Related Guides and Resources
More from Cure MD Billers
- CPT Code 80061: Complete Lipid Panel Billing Guide
- 99203 CPT Code: Billing, Time & Reimbursement Guide
- 99214 CPT Code Guide
- CPT Code for Renal Ultrasound: 76770 vs 76775
Frequently Asked Questions
What is the ICD-10 code for hypothyroidism unspecified?
E03.9, Hypothyroidism, unspecified. It also includes myxedema NOS.
Is E03.9 a billable code?
Yes. E03.9 is a billable, specific ICD-10-CM code and can serve as the principal diagnosis.
What is the ICD-10 code for acquired hypothyroidism?
E03.9, because the Alphabetic Index routes “Hypothyroidism (acquired)” there. Use E03.4 only for documented acquired thyroid atrophy.
What is the ICD-10 code for secondary hypothyroidism?
E03.8, Other specified hypothyroidism. Add E23.0 when the provider documents hypopituitarism.
What is the ICD-10 code for primary hypothyroidism?
E03.9 when no cause is stated. Code the cause instead when it is documented, such as E06.3 for Hashimoto’s.
What is the ICD-10 code for congenital hypothyroidism?
E03.1 without goiter or E03.0 with diffuse goiter. Transient neonatal cases use P72.2.
What is the ICD-10 code for history of hypothyroidism?
Z86.39, but only for resolved cases with no current treatment. Patients on levothyroxine stay on E03.9.
What is the ICD-10 code for family history of hypothyroidism?
Z83.49, Family history of other endocrine, nutritional and metabolic diseases.
What is the ICD-10 code for Hashimoto’s hypothyroidism?
E06.3, Autoimmune thyroiditis.
What is the ICD-10 code for hypothyroidism after thyroidectomy?
E89.0, Postprocedural hypothyroidism.
What is the ICD-9 equivalent of E03.9?
ICD-9-CM 244.9, Unspecified hypothyroidism. In ICD-11, hypothyroidism falls under 5A00.
Did E03.9 change in the FY2027 update?
No. All E03 codes remain unchanged for October 1, 2026 through September 30, 2027.
