How to tell if someone is high functioning autistic?

The term high functioning autistic is not an official diagnostic term and is no longer used in the DSM-5, which now uses autism spectrum disorder with levels of support needs, but it is still used informally to describe autistic people who speak fluently and have average or above average intellectual abilities and need less daily support. Some common patterns that may be noticed include fluent language with differences in pragmatic communication, such as taking things literally, missing sarcasm, or having difficulty with unwritten social rules and small talk, intense and deep interests in specific subjects, preference for routine and predictability and distress when plans change suddenly, sensory sensitivities to noise, lights, textures, or crowds, and a tendency to mask by consciously copying social behaviors which can lead to exhaustion. They may be successful at school or work but struggle with social burnout, executive function like organization and time management, and maintaining friendships. It is not possible to tell if someone is autistic from observation alone, and functioning labels can be misleading because support needs vary by situation. If you are concerned about yourself or someone else, a referral to a psychologist, psychiatrist, or neuropsychologist experienced in adult autism evaluation can provide a more accurate and respectful assessment.