Venomous Insect Sting or Bite: A T63 Toxic-Effect Code, Not an Injury Code — and No W57

The Alphabetic Index does not list venomous stings under “Bite” or “Sting” with a code. Both entries redirect: “Sting (venomous) (with allergic or anaphylactic shock) — see Table of Drugs and Chemicals, by animal or substance, poisoning,” and “Venom, venomous — see Table of Drugs and Chemicals, by animal or substance, poisoning.” In the Table, each animal has its own row, and the four filled columns are the four intents:

The adverse-effect and underdosing columns are empty for every venom row — a sting is never “correctly administered.” Each code then takes the 7th character for the encounter (A, D, S). Category T63’s Includes note is the definition: “bite or touch of venomous animal,” “pricked or stuck by thorn or leaf.”

The counterpart is the ordinary insect bite. The Index entry “Bite, insect” sends the coder to “Bite, by site, superficial, insect,” which lands in the injury chapter — for example S30.861A, Insect bite (nonvenomous) of abdominal wall — and that injury takes an external cause code, W57, “Bitten or stung by nonvenomous insect and other nonvenomous arthropods.” The record’s word decides the path: venomous goes to the Table, nonvenomous goes by site.

Section I.C.19.e.5.d sets the order: “When coding a toxic effect, assign the toxic effect code first, followed by codes for all associated manifestations of the toxic effect.” The T51–T65 section repeats it as a Use Additional Code note for “all associated manifestations,” and T63.4 names the one that matters most: “Use additional code, if applicable, for anaphylactic shock (T78.2).”

What must not be added is an external cause code from W50–W64. Two notes say so, and so does the guideline. The W50–W64 section carries an Excludes1 for “Toxic effect of contact with venomous animals and plants (T63.-)”; W57 carries its own Excludes1 for “contact with venomous insects and arthropods (T63.2-, T63.3-, T63.4-)”; and Section I.C.19.e states that T36–T65 “are combination codes that include the substance that was taken as well as the intent. No additional external cause code is required for poisonings, toxic effects, adverse effects and underdosing codes.” A T63 code with a W57 code beside it is the single most common way this family is miscoded — the intent the W code would add is already the T63 code’s 6th character.

1. Bee sting while gardening; anaphylactic shock documented; emergency treatment.T63.441A, Toxic effect of venom of bees, accidental, initial encounter — first — then T78.2XXA, Anaphylactic shock, unspecified, initial encounter, per T63.4’s Use Additional Code note. No W code.
2. Mosquito bites on the abdomen, itching, no envenomation documented. Nonvenomous: S30.861A, Insect bite (nonvenomous) of abdominal wall, initial encounter, with W57.XXXA as the external cause. No T63 code.
3. “Stung by something venomous,” insect not identified. The Table’s unspecified row: T63.91XA, Toxic effect of contact with unspecified venomous animal, accidental, initial encounter — or T63.481A if the record says a venomous insect or arthropod without naming it.

1. Determine whether the record says venomous. Venomous → the Table of Drugs row for the animal (bee, wasp, insect, venom NOS) → T63.4-/T63.9- with the intent character; nonvenomous → a superficial injury code by site.
2. Verify the T63 code in the Tabular and add the 7th character for the encounter.
3. Add codes for the manifestations after the T63 code — T78.2 for anaphylactic shock per T63.4’s Use Additional Code note.
4. Do not add a W50–W64 external cause code to a T63 code; add W57 only to a nonvenomous bite injury.

• W57 beside a T63 code.
• An S-code insect bite for a documented venomous sting.
• T63.4- for a mosquito bite with no envenomation documented.
• Sequencing anaphylactic shock before the venom code.

• The word “venomous,” and the animal, which selects the Table row.
• Anaphylactic shock or other manifestations.
• The site, for a nonvenomous bite.
• Intent, for the rare non-accidental case.