Billable / Specific Code
ICD-10-CM T65.821 is the diagnosis code for Toxic effect of harmful algae and algae toxins, accidental (unintentional). This code falls under the section "Toxic effects of substances chiefly nonmedicinal as to source" within Chapter 19 — Injury, poisoning and certain other consequences of external causes (S00-T88). It is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes. Medical coders and healthcare providers use this code to document and classify diagnoses in electronic health records, insurance claims, and clinical databases.
Understanding where T65.821 sits in the ICD-10-CM classification helps ensure proper coding:
Yes, T65.821 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
T65.821 is the ICD-10-CM diagnosis code for "Toxic effect of harmful algae and algae toxins, accidental (unintentional)". It is used by healthcare providers to classify and document this condition in medical records and insurance claims.
The parent code of T65.821 is T65.82 ("Toxic effect of harmful algae and algae toxins"). T65.821 provides a more specific classification within this category.
T65.821 is located in Section T51-T65 — "Toxic effects of substances chiefly nonmedicinal as to source" within Chapter 19 of the ICD-10-CM Tabular List.
Use T65.821 when the patients documented diagnosis matches "Toxic effect of harmful algae and algae toxins, accidental (unintentional)" and the clinical documentation supports this level of specificity. Always verify with the latest ICD-10-CM guidelines and payer requirements.
The ICD-10-CM code for Toxic effect of harmful algae and algae toxins, accidental (unintentional) is T65.821.
Yes, T65.821 can be used as a primary diagnosis code since it is billable and specific.
T65.821 is in Chapter 19 of the ICD-10-CM Tabular List.
Yes, T65.821 is a valid ICD-10-CM code for the 2026 fiscal year, subject to official CMS updates.