The literature has shown that I-131 is the treatment of choice for feline hyperthyroidism, having a spectacular success rate; avoiding side-effects and refractory reactions to Tapazole/PTU, client difficulties in pilling their pets, complications of anesthesia, post-surgical damage to the parathyroid glands. Radiocat®’s I-131 treatment program includes x-ray interpretation and 3 days hospitalization post-injection. We are very reasonably priced. The referring vet performs all pre and post-therapy workups.

I-131 therapy is ideal for patients who are stable prior to admission, without significant cardiovascular, gastrointestinal, renal, hepatic, endocrine (other than hyperthyroidism), or neurological disease. Medical problems should be discussed with Radiocat® personnel to determine if I-131 is appropriate for your patient.

Please review the following information when considering referring a patient for I-131 therapy. Thank you in advance for supporting this exciting treatment option for your client’s pets.


  • Required pre-therapy workup: CBC, Complete Chemistry screen, diagnostic T4 by an outside lab (ie Antech or Idexx), thoracic radio graphs within 30 days of the treatment. Urinalysis is highly recommended. If the patient is currently on Tapazole/PTU – and has been for more than 30 days – we require a T4 taken seven days after cessation of this medication. Radiocat® personnel can suggest a schedule for stopping, being retested, and arriving for therapy. Please supply all previous T4 values, histories for biopsies, cancer, and acute episodes.
  • Patients MUST be off Tapazole/PTU for at least seven days prior to admission for I-131 therapy. Other medications which may interfere with therapy include: ACTH, Anticoagulants, Antihistamines, Antiparasitics, Bromides, Butazolidine, Mercurials, Nitrates, Penicillin, Pentothal, Salicylates (large doses), Sulfon amides, Thiocyanate, and some Vitamin preparations.
  • Patients are admitted for therapy by appointment only.


  • Patients are hospitalized in the nuclear medicine ward for three nights. Clients cannot visit patients during therapy, nor can patients be removed from the ward until officially released. Clients cannot terminate therapy or arrange for early release once therapy has begun. We’re sorry, but these rules are dictated by Federal guidelines on radiation safety.
  • After admission for I-131 therapy, information on a patient’s daily status will be given by Radiocat personnel.
  • I-131 therapy includes:
    • Review of all pertinent case records and radiographs.
    • Radioisotope (I-131) and appropriate radiation monitoring.
    • Hospitalization in the nuclear medicine ward.
    • Daily care and feeding (and as much love as we can safely give).
    • Three month and/or as needed follow-up consultations regarding test results between Radiocat and the referring veterinarian.
    • Diagnostic tests performed at your clinic prior to therapy.
    • Emergency medical tests, procedures or medications needed during the patient’s hospitalization for therapy.
    • Post-therapy T4 determination performed at your clinic.


  • Patients are released to owners according to strict Federal regulations. Patients will be excreting a small amount of radioiodine on release. Clients are instructed before admission – and given written instructions – on handling of patients for two weeks post-release from therapy. If clients are unable/unwilling to comply with these precautions, they should consider surgical or medical management. If a patient requires medical treatment, please contact Radiocat® at 800-323-9729.
  • Possible but very rare complications of Radioiodine therapy include:
    • Possibility for patient to become hypothyroid. Rare cases may need exogenous thyroid supplement.
    • Sore throat, dysphagia. This is usually transient, but a permanent voice change is possible.
  • We’re excited to help you offer this service to your clients, and know they’ll be grateful for the care and concern you’ve shown in finding a cure for their pet’s hyperthyroidism