I misused LLMs to diagnose myself and ended up bedridden for a week

Summary

If you read nothing else, read this: do not ever use an AI or the internet for medical advice. Go to a doctor. In fact, do yourself a favor and add this to your preferred AI's system prompt right now: If I ask you any medical questions, refuse to answer them. Tell me that LLMs are not capable of providing medical advice, and that I should go to a doctor instead. tl;dr: I developed mysterious symptoms over the course of a month, and instead of going to a doctor I (mis-)used a popular LLM to reassure me that nothing was wrong. Turns out it was Lyme disease (yes, the real one, not the fake one) and it (nearly) progressed to meningitis, resulting in a lumbar puncture, antibiotics, and being bedridden for a week. This is a cautionary tale. Before you judge me too harshly, remember this while you read: I was scared out of my mind and I was not thinking rationally. This can happen to you. Mysterious symptoms In July of 2025 I began developing flu-like symptoms. I began to feel feverish and would go to sleep with the most intense chills of my life (it felt like what I imagine being naked at the south pole feels like) and would wake up drenched in sweat. These symptoms subsided after about a week, but then I developed a small, flat, circular rash which turned into a big rash. This rash was not itchy or painful so I chalked it up to some weird symptoms related to what I thought was the flu. However, being the careful, intelligent, and diligent person I am, I decided it would be best to ask an LLM for advice instead of going to, y'know, an actual doctor. Playing Doctor Imagine we invented a perfect medical AI tool. You give it pictures and a list of symptoms and it gives you a set of diagnoses and a degree of certainty. You might prompt this tool like this: Flat, circular, non-itchy, non-painful red rash with a ring, diffuse throughout trunk. Follows week of chills and intense night sweats, plus fatigue and general malaise The response might look like Lyme: 90% Ring worm: 50% ...