ICD-10-CM Diagnosis Code T36.4X6A - Underdosing of tetracyclines, initial encounter (original) (raw)

ICD List 2025-2026 Edition

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6. 2026 ICD-10-CM Code T36.4X6A

Underdosing of tetracyclines, initial encounter

ICD-10-CM Code:

T36.4X6A

ICD-10 Code for:

Underdosing of tetracyclines, initial encounter

Is Billable?

Yes - Valid for Submission

Chronic Condition Indicator: [1]

Not chronic

Code Navigator:

T36.4X6A is a billable diagnosis code used to specify a medical diagnosis of underdosing of tetracyclines, initial encounter. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2025 through September 30, 2026.

This code describes a circumstance which influences the patient's health status but not a current illness or injury. The code is unacceptable as a principal diagnosis.

T36.4X6A is an initial encounter code, includes a 7th character and should be used while the patient is receiving active treatment for a condition like underdosing of tetracyclines. According to ICD-10-CM Guidelines an "initial encounter" doesn't necessarily means "initial visit". The 7th character should be used when the patient is undergoing active treatment regardless if new or different providers saw the patient over the course of a treatment. The appropriate 7th character codes should also be used even if the patient delayed seeking treatment for a condition.

1. Code Information
2. Clinical Classification
3. Clinical Information
4. Coding Guidelines
5. Tabular List of Diseases and Injuries
6. Code Edits
7. Convert to ICD-9 Code
8. Table of Drugs and Chemicals
9. Patient Education
10. Other Codes Used Similar Conditions
11. Code History

• Injury, poisoning and certain other consequences of external causes
  S00–T88
  • Poisoning by, adverse effect of and underdosing of drugs, medicaments and biological substances
    T36-T50
    * Poisoning by, adverse effect of and underdosing of systemic antibiotics
    T36

Clinical Classifications group individual ICD-10-CM diagnosis codes into broader, clinically meaningful categories. These categories help simplify complex data by organizing related conditions under common clinical themes.

They are especially useful for data analysis, reporting, and clinical decision-making. Even when diagnosis codes differ, similar conditions can be grouped together based on their clinical relevance. Each category is assigned a unique CCSR code that represents a specific clinical concept, often tied to a body system or medical specialty.

CCSR Code: INJ029

Inpatient Default: X - Not applicable.

Outpatient Default: X - Not applicable.

• Chlortetracycline

a tetracycline with a 7-chloro substitution.

• Demeclocycline

a tetracycline analog having a 7-chloro and a 6-methyl. because it is excreted more slowly than tetracycline, it maintains effective blood levels for longer periods of time.

• Doxycycline

a synthetic tetracycline derivative with similar antimicrobial activity.

• Lymecycline

a semisynthetic antibiotic related to tetracycline. it is more readily absorbed than tetracycline and can be used in lower doses.

• Methacycline

a broad-spectrum semisynthetic antibiotic related to tetracycline but excreted more slowly and maintaining effective blood levels for a more extended period.

• Minocycline

a tetracycline analog, having a 7-dimethylamino and lacking the 5 methyl and hydroxyl groups, which is effective against tetracycline-resistant staphylococcus infections.

• Oxytetracycline

a tetracycline analog isolated from the actinomycete streptomyces rimosus and used in a wide variety of clinical conditions.

• Rolitetracycline

a pyrrolidinylmethyl tetracycline.

• Tetracycline

a naphthacene antibiotic that inhibits amino acyl trna binding during protein synthesis.

• Tetracycline Resistance

nonsusceptibility of bacteria to the action of tetracycline which inhibits aminoacyl-trna binding to the 30s ribosomal subunit during protein synthesis.

• Tetracyclines

closely congeneric derivatives of the polycyclic naphthacenecarboxamide. (gilman et al., goodman and gilman's the pharmacological basis of therapeutics, 8th ed, p1117)

Underdosing refers to taking less of a medication than is prescribed by a provider or a manufacturer's instruction. Codes for underdosing should never be assigned as principal or first-listed codes. If a patient has a relapse or exacerbation of the medical condition for which the drug is prescribed because of the reduction in dose, then the medical condition itself should be coded.

The appropriate 7th character is to be added to each code from block Poisoning by, adverse effect of and underdosing of systemic antibiotics (T36). Use the following options for the aplicable episode of care:

• A - initial encounter
• D - subsequent encounter
• S - sequela

The Medicare Code Editor (MCE) detects errors and inconsistencies in ICD-10-CM diagnosis coding that can affect Medicare claim validity. These Medicare code edits help medical coders and billing professionals determine when a diagnosis code is not appropriate as a principal diagnosis, does not meet coverage criteria. Use this list to verify whether a code is valid for Medicare billing and to avoid claim rejections or denials due to diagnosis coding issues.

There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Below are the ICD-9 codes that most closely match this ICD-10 code, based on the General Equivalence Mappings (GEMs). This ICD-10 to ICD-9 crosswalk tool is helpful for coders who need to reference legacy diagnosis codes for audits, historical claims, or approximate code comparisons.

ICD-9-CM:

Approximate Flag - The approximate mapping means this ICD-10 code does not have an exact ICD-9 equivalent. The matched code is the closest available option, but it may not fully capture the original diagnosis or clinical intent.

The parent code T36.4X6 of the current diagnosis code is referenced in the Table of Drugs and Chemicals, this table contains a classification of drugs, industrial solvents, corrosive gases, noxious plants, pesticides, and other toxic agents.

According to ICD-10-CM coding guidelines it is advised to do not code directly from the Table of Drugs and Chemicals, instead always refer back to the Tabular List when doing the initial coding. Each substance in the table is assigned a code according to the poisoning classification and external causes of adverse effects. It is important to use as many codes as necessary to specify all reported drugs, medicinal or chemical substances. If the same diagnosis code describes the causative agent for more than one adverse reaction, poisoning, toxic effect or underdosing, utilize the code only once.

Filter table of drugs and chemicals:

Antibiotics

What are antibiotics?

Antibiotics are medicines that fight bacterial infections in people and animals. They work by killing the bacteria or by making it hard for the bacteria to grow and multiply.

Antibiotics can be taken in different ways:

• Orally (by mouth). This could be pills, capsules, or liquids.
• Topically. This might be a cream, spray, or ointment that you put on your skin. It could also be eye ointment, eye drops, or ear drops.
• Through an injection or intravenously (IV). This is usually for more serious infections.

What do antibiotics treat?

Antibiotics only treat certain bacterial infections, such as strep throat, urinary tract infections, and E. coli.

You may not need to take antibiotics for some bacterial infections. For example, you might not need them for many sinus infections or some ear infections. Taking antibiotics when they're not needed won't help you, and they can have side effects. Your health care provider can decide the best treatment for you when you're sick. Don't ask your provider to prescribe an antibiotic for you.

Do antibiotics treat viral infections?

Antibiotics do not work on viral infections. For example, you shouldn't take antibiotics for:

• Colds and runny noses, even if the mucus is thick, yellow, or green
• Most sore throats (except strep throat)
• Flu
• Most cases of bronchitis

What are the side effects of antibiotics?

The side effects of antibiotics range from minor to very severe. Some of the common side effects include:

• Rash
• Nausea
• Diarrhea
• Yeast infections

More serious side effects can include:

• C. diff infections, which cause diarrhea that can lead to severe colon damage and sometimes even death
• Severe and life-threatening allergic reactions
• Antibiotic resistance infections

Call your health care provider if you develop any side effects while taking your antibiotic.

Why is it important to take antibiotics only when they're needed?

You should only take antibiotics when they are needed because they can cause side effects and can contribute to antibiotic resistance. Antibiotic resistance happens when the bacteria change and become able to resist the effects of an antibiotic. This means that the bacteria continue to grow.

How do I use antibiotics correctly?

When you take antibiotics, it is important that you take them responsibly:

• Always follow the directions carefully. Finish your medicine even if you feel better. If you stop taking them too soon, some bacteria may survive and re-infect you.
• Don't save your antibiotics for later.
• Don't share your antibiotic with others.
• Don't take antibiotics prescribed for someone else. This may delay the best treatment for you, make you even sicker, or cause side effects.

Centers for Disease Control and Prevention

[Learn More in MedlinePlus]

• FY 2026 - No Change, effective from 10/1/2025 through 9/30/2026

• FY 2025 - No Change, effective from 10/1/2024 through 9/30/2025

• FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024

• FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023

• FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022

• FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021

• FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020

• FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019

• FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018

• FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017

• FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.

• Previous Code: T36.4X6

• Parent Code: T36.4X6

• Next Code: T36.4X6D