Poisoning, Adverse Effects, and Underdosing ICD-10-CM codes

Every code in T36 through T50 identifies the drug in the fourth and fifth characters and then reports the circumstance in the sixth: 1 accidental (unintentional) poisoning, 2 intentional self-harm, 3 assault, 4 undetermined, 5 adverse effect, 6 underdosing. When the drug subcategory has only four characters, X fills the fifth, as in T39.1X1A (acetaminophen poisoning, accidental) or T42.4X1A (benzodiazepines). The seventh character is A initial, D subsequent, or S sequela. Undetermined intent (4) is used only when the record states the intent could not be determined; when intent is simply not documented, the default is accidental.

Poisoning means the drug was taken in error, in overdose, by the wrong person, or with alcohol or another drug it should not be combined with. The T code is sequenced first, followed by the manifestations. Opioid overdoses illustrate the drug axis: T40.2X1A other opioids such as oxycodone and hydrocodone, T40.411A fentanyl, T40.1X1A heroin, T40.601A unspecified narcotic; add the F11 code for opioid use, abuse, or dependence (F11.20) when documented. T50.901A is the accidental poisoning code for an unspecified drug.

An adverse effect is a reaction to a drug that was correctly prescribed and properly taken. The manifestation is sequenced first (for example L27.0 for a drug eruption), followed by the T code with the character 5 (T36.0X5A penicillins, T39.395A other NSAIDs, T50.905A unspecified drug). T88.7XXA is the unspecified adverse effect of a drug, and T88.6XXA is anaphylaxis from a correctly administered drug. Underdosing (character 6) means the patient took less than prescribed; it is never a principal diagnosis. Code the condition that worsened first, then the underdosing code, then a Z91.12- or Z91.13- code for the reason (Z91.120 intentional due to financial hardship, Z91.128 other intentional, Z91.130 unintentional due to age-related debility).