ICD-10-CM > S00-T88 > T51-T65 > T65 > T65.8 > T65.82 > T65.821 T65.821 Toxic effect of harmful algae and algae toxins, accidental (unintentional) Non-Billable/Non-Specific Applicable To Toxic effect of harmful algae and algae toxins NOS Codes T65.821A..., initial encounterT65.821D..., subsequent encounterT65.821S..., sequela