T65.821A Toxic effect of harmful algae and algae toxins, accidental (unintentional), initial encounter

Billable ICD-10-CM code, FY2026.

Built from T65.821 with 7th character A (initial encounter).

Applies from T65 Toxic effect of other and unspecified substances

7th character note

• The appropriate 7th character is to be added to each code from category T65

7th character required

• A — initial encounter
• D — subsequent encounter
• S — sequela

Applies from T65.82 Toxic effect of harmful algae and algae toxins

Applicable to

• Toxic effect of (harmful) algae bloom NOS
• Toxic effect of blue-green algae bloom
• Toxic effect of brown tide
• Toxic effect of cyanobacteria bloom
• Toxic effect of Florida red tide
• Toxic effect of pfiesteria piscicida
• Toxic effect of red tide

Applies from T65.821 Toxic effect of harmful algae and algae toxins, accidental (unintentional)

Applicable to

• Toxic effect of harmful algae and algae toxins NOS

Code annotations containing back-references to T65.821A

Back-references to T65.82

• Type 1 Excludes: T61 Toxic effect of noxious substances eaten as seafood ("toxic effect of harmful algae bloom (T65.82-)")
• Type 1 Excludes: T61 Toxic effect of noxious substances eaten as seafood ("toxic effect of red tide (T65.82-)")

Back-references to T65

• Code First: D61.2 Aplastic anemia due to other external agents (", if applicable, toxic effects of substances chiefly nonmedicinal as to source (T51-T65)")
• Code First: D64.2 Secondary sideroblastic anemia due to drugs and toxins ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: E03.2 Hypothyroidism due to medicaments and other exogenous substances ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: E09 Drug or chemical induced diabetes mellitus ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: F02 Dementia in other diseases classified elsewhere ("intoxications (T36-T65)")
• Code First: G21.2 Secondary parkinsonism due to other external agents ("(T51-T65) to identify external agent")
• Code First: G62.2 Polyneuropathy due to other toxic agents ("(T51-T65) to identify toxic agent")
• Code First: G70.1 Toxic myoneural disorders ("(T51-T65) to identify toxic agent")
• Code First: G72.2 Myopathy due to other toxic agents ("(T51-T65) to identify toxic agent")
• Code First: G92.8 Other toxic encephalopathy ("poisoning due to drug or toxin, if applicable, (T36-T65 with fifth or sixth character 1-4)")
• Code First: G92.9 Unspecified toxic encephalopathy ("poisoning due to drug or toxin, if applicable, (T36-T65 with fifth or sixth character 1-4)")
• Code First: H10.21 Acute toxic conjunctivitis ("(T51-T65) to identify chemical and intent")
• Code First: H35.38 Toxic maculopathy ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: H46.3 Toxic optic neuropathy ("(T51-T65) to identify cause")
• Code First: H91.0 Ototoxic hearing loss ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: I42.7 Cardiomyopathy due to drug and external agent ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: J68 Respiratory conditions due to inhalation of chemicals, gases, fumes and vapors ("(T51-T65) to identify cause")
• Code First: J69.1 Pneumonitis due to inhalation of oils and essences ("(T51-T65) to identify substance")
• Code First: J69.8 Pneumonitis due to inhalation of other solids and liquids ("(T51-T65) to identify substance")
• Code First: J70.8 Respiratory conditions due to other specified external agents ("(T51-T65) to identify the external agent")
• Code First: J70.9 Respiratory conditions due to unspecified external agent ("(T51-T65) to identify the external agent")
• Code First: J84.89 Other specified interstitial pulmonary diseases ("poisoning due to drug or toxin (T51-T65 with fifth or sixth character to indicate intent), for toxic pneumonopathy")
• Code First: K22.1 Ulcer of esophagus ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: K52.1 Toxic gastroenteritis and colitis ("(T51-T65) to identify toxic agent")
• Code First: K59.3 Megacolon, not elsewhere classified (", if applicable (T51-T65) to identify toxic agent")
• Code First: K71 Toxic liver disease ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: L53.0 Toxic erythema ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: M34.2 Systemic sclerosis induced by drug and chemical ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: N14 Drug- and heavy-metal-induced tubulo-interstitial and tubular conditions ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: P58.4 Neonatal jaundice due to drugs or toxins transmitted from mother or given to newborn ("poisoning due to drug or toxin, if applicable (T36-T65 with fifth or sixth character 1-4)")
• Code First: T20.4 Corrosion of unspecified degree of head, face, and neck ("(T51-T65) to identify chemical and intent")
• Code First: T20.5 Corrosion of first degree of head, face, and neck ("(T51-T65) to identify chemical and intent")
• Code First: T20.6 Corrosion of second degree of head, face, and neck ("(T51-T65) to identify chemical and intent")
• Code First: T20.7 Corrosion of third degree of head, face, and neck ("(T51-T65) to identify chemical and intent")
• Code First: T21.4 Corrosion of unspecified degree of trunk ("(T51-T65) to identify chemical and intent")
• Code First: T21.5 Corrosion of first degree of trunk ("(T51-T65) to identify chemical and intent")
• Code First: T21.6 Corrosion of second degree of trunk ("(T51-T65) to identify chemical and intent")
• Code First: T21.7 Corrosion of third degree of trunk ("(T51-T65) to identify chemical and intent")
• Code First: T22.4 Corrosion of unspecified degree of shoulder and upper limb, except wrist and hand ("(T51-T65) to identify chemical and intent")
• Code First: T22.5 Corrosion of first degree of shoulder and upper limb, except wrist and hand ("(T51-T65) to identify chemical and intent")
• Code First: T22.6 Corrosion of second degree of shoulder and upper limb, except wrist and hand ("(T51-T65) to identify chemical and intent")
• Code First: T22.7 Corrosion of third degree of shoulder and upper limb, except wrist and hand ("(T51-T65) to identify chemical and intent")
• Code First: T23.4 Corrosion of unspecified degree of wrist and hand ("(T51-T65) to identify chemical and intent")
• Code First: T23.5 Corrosion of first degree of wrist and hand ("(T51-T65) to identify chemical and intent")
• Code First: T23.6 Corrosion of second degree of wrist and hand ("(T51-T65) to identify chemical and intent")
• Code First: T23.7 Corrosion of third degree of wrist and hand ("(T51-T65) to identify chemical and intent")
• Code First: T24.4 Corrosion of unspecified degree of lower limb, except ankle and foot ("(T51-T65) to identify chemical and intent")
• Code First: T24.5 Corrosion of first degree of lower limb, except ankle and foot ("(T51-T65) to identify chemical and intent")
• Code First: T24.6 Corrosion of second degree of lower limb, except ankle and foot ("(T51-T65) to identify chemical and intent")
• Code First: T24.7 Corrosion of third degree of lower limb, except ankle and foot ("(T51-T65) to identify chemical and intent")
• Code First: T25.4 Corrosion of unspecified degree of ankle and foot ("(T51-T65) to identify chemical and intent")
• Code First: T25.5 Corrosion of first degree of ankle and foot ("(T51-T65) to identify chemical and intent")
• Code First: T25.6 Corrosion of second degree of ankle and foot ("(T51-T65) to identify chemical and intent")
• Code First: T25.7 Corrosion of third degree of ankle and foot ("(T51-T65) to identify chemical and intent")
• Code First: T26.5 Corrosion of eyelid and periocular area ("(T51-T65) to identify chemical and intent")
• Code First: T26.6 Corrosion of cornea and conjunctival sac ("(T51-T65) to identify chemical and intent")
• Code First: T26.7 Corrosion with resulting rupture and destruction of eyeball ("(T51-T65) to identify chemical and intent")
• Code First: T26.8 Corrosions of other specified parts of eye and adnexa ("(T51-T65) to identify chemical and intent")
• Code First: T26.9 Corrosion of eye and adnexa, part unspecified ("(T51-T65) to identify chemical and intent")
• Code First: T27.4 Corrosion of larynx and trachea ("(T51-T65) to identify chemical and intent")
• Code First: T27.5 Corrosion involving larynx and trachea with lung ("(T51-T65) to identify chemical and intent")
• Code First: T27.6 Corrosion of other parts of respiratory tract ("(T51-T65) to identify chemical and intent")
• Code First: T27.7 Corrosion of respiratory tract, part unspecified ("(T51-T65) to identify chemical and intent")
• Code First: T28.5 Corrosion of mouth and pharynx ("(T51-T65) to identify chemical and intent")
• Code First: T28.6 Corrosion of esophagus ("(T51-T65) to identify chemical and intent")
• Code First: T28.7 Corrosion of other parts of alimentary tract ("(T51-T65) to identify chemical and intent")
• Code First: T28.8 Corrosion of internal genitourinary organs ("(T51-T65) to identify chemical and intent")
• Code First: T28.9 Corrosions of other and unspecified internal organs ("(T51-T65) to identify chemical and intent")
• Type 2 Excludes: T81 Complications of procedures, not elsewhere classified ("poisoning and toxic effects of drugs and chemicals (T36-T65 with fifth or sixth character 1-4)")
• Type 2 Excludes: T88 Other complications of surgical and medical care, not elsewhere classified ("poisoning and toxic effects of drugs and chemicals (T36-T65 with fifth or sixth character 1-4)")
• Type 2 Excludes: Z77 Other contact with and (suspected) exposures hazardous to health ("toxic effects of substances chiefly nonmedicinal as to source (T51-T65)")

Nearby codes

• T65.814A Toxic effect of latex, undetermined, initial encounter
• T65.814D Toxic effect of latex, undetermined, subsequent encounter
• T65.814S Toxic effect of latex, undetermined, sequela
• T65.82 Toxic effect of harmful algae and algae toxins
• T65.821 Toxic effect of harmful algae and algae toxins, accidental (unintentional)
• T65.821A Toxic effect of harmful algae and algae toxins, accidental (unintentional), initial encounter (this code)
• T65.821D Toxic effect of harmful algae and algae toxins, accidental (unintentional), subsequent encounter
• T65.821S Toxic effect of harmful algae and algae toxins, accidental (unintentional), sequela
• T65.822 Toxic effect of harmful algae and algae toxins, intentional self-harm
• T65.822A Toxic effect of harmful algae and algae toxins, intentional self-harm, initial encounter
• T65.822D Toxic effect of harmful algae and algae toxins, intentional self-harm, subsequent encounter