You may qualify for a service animal if you have a disability as defined by the Americans with Disabilities Act (ADA), and a dog (or rarely, a miniature horse) can be trained to perform specific tasks that directly mitigate your disability.
Key qualification criteria:
You have a disability: A physical, sensory, psychiatric, intellectual, or mental impairment that substantially limits one or more major life activities (e.g., walking, seeing, hearing, thinking, concentrating, sleeping, working, or self-care). Mental health conditions like PTSD, severe anxiety, depression, or bipolar disorder can qualify if they meet this threshold.
Task-trained animal: The animal must perform specific work or tasks related to your disability (e.g., guiding the blind, alerting to seizures, deep pressure therapy for panic attacks, interrupting dissociative episodes, or retrieving medication). Mere emotional comfort or presence does not qualify—this distinguishes service animals from emotional support animals (ESAs).
No doctor's letter, certification, or registration is required under the ADA—qualification is based on your disability and the animal's trained tasks. You (or a trainer) can train the animal yourself; professional training isn't mandatory.