Pets and humans can both suffer from over or under active thyroid glands, and therefore be prescribed a thyroid medication. When given for a chronic thyroid condition, these medications are generally very safe. In fact, dogs often require a higher dose of medication to correct a thyroid problem than humans do. This means that, unlike most medications used in both human and veterinary medicine, there is a much wider margin of safety if pets get into a human prescription accidentally or if they accidentally receive an extra dose. However, if a large acute overdose is suspected, elevated heart rate, nervousness, panting, severe agitation or aggression, tremors, and seizures may be seen.