Adverse Effect

When coding an adverse effect of a drug that has been correctly prescribed and properly administered, assign the appropriate code for the nature of the adverse effect followed by the appropriate code for the adverse effect of the drug (T36-T50).


When coding a poisoning or reaction to the improper use of a medication (overdose, wrong substance given or taken in error, wrong route of administration), first assign the appropriate code from categories T36-T50. The poisoning codes have an associated intent as their 5th or 6th character (accidental, intentional self-harm, assault and undetermined. If the intent of the poisoning is unknown or unspecified, code the intent as accidental intent. The undetermined intent is only for use if the documentation in the record specifies that the intent cannot be determined.

Use additional code(s) for all manifestations of poisonings. If there is also a diagnosis of abuse or dependence of the substance, the abuse or dependence is assigned as an additional code.


Underdosing means that a patient has taken less of a medication than is prescribed by the provider or the manufacturer’s instruction. For underdosing, use a code from categories T36-T50 (fifth or sixth character “6”) Codes for noncompliance (Z91.12-, Z91.13-) or complication of care (Y63.6-Y63.9) codes are to be used with an underdosing code to indicate intent, if known.

Toxic Effects

When a harmful substance is ingested or comes in contact with a person, this is classified as a toxic effect. The toxic effect codes are in categories T51-T65. Toxic effect codes have an associated intent: accidental, intentional self-harm, assault and undetermined. Toxic effects are for nonmedicinal substances & should be sequenced first, followed by code(s) for all manifestations. When no intent is indicated, you should code as accidental.

Coding Scenario #1

A 43-year-old female presents to the ED with palpitations & dizziness. She states that she started taking a new medicine called hydrochlorothiazide for her hypertension two weeks ago. She says that she is taking the medication as directed. She does admit to having 2 martinis with her dinner this evening.

Final Impression:
Palpitations and dizziness secondary to Hydrochlorothiazide reaction
Condition: Good
Disposition: Home
Counseled: Patient, Regarding diagnosis and medication. Patient indicated understanding of instructions.

How should this be coded?

T50.2X1A Poisoning by carbonic-anhydrase inhibitors, benzothiadiazides and other diuretics, accidental (unintentional)
R00.2 Palpitations
R42 Dizziness
I10 Hypertension

Coding Scenario #2

A 76 year old female presents to the ED with complaints of edema and SOB. She states that she has chronic CHF and is currently on Lasix. Over the weekend she went to Branson, Missouri on a guided tour with several friends. She admittedly reports that she did not take her Lasix the day she left for Missouri or on the day she returned home. She states that she was worried that she would need to make several stops to use the restroom and did not want to be a burden.

Final Impression:
Acute exacerbation of systolic heart failure
Condition: Stable
Disposition: Admit to observation unit
Counseled: Patient, Regarding diagnosis and medication. Patient indicated understanding of instructions.

How should this be coded?

T50.1X6A Underdosing of loop [high-ceiling] diuretics
I50.23 Acute on chronic systolic (congestive) heart failure
Z91.128 Patient’s intentional underdosing of medication regimen for other reason


2017 ICD-10-CM & CPT Coding guidelines
Clintegrity 360 Encoder


Apply for a Job with MedPartners

Looking for a New Career? We’d love to hear from you. Please click “apply” to submit a cover letter and resume.
  • * All indicated fields must be completed.
    Please include non-medical questions and correspondence only.

    By providing your mobile phone number, you are consenting to receive text messages from AMN Healthcare. You can unsubscribe at any time by texting “STOP”. Texts are free, though standard text message fees from your cell phone provider may apply. See privacy policy for details.

    By clicking “SUBMIT”, I agree to receive emails, automated text messages and phone calls (including calls that contain prerecorded content) from and on behalf of AMN Healthcare Revenue Cycle Solutions (formerly MedPartners), its parent, AMN Healthcare, and affiliates. I understand these messages will be to the email or phone number provided, and will be about employment opportunities, positions in which I’ve been placed, and my employment with AMN companies. See privacy policy for details.