How to use a symptom checker safely
Online symptom checkers are educational maps, not diagnoses. They're useful for two things: (1) deciding whether you need urgent care versus a routine appointment, and (2) preparing better questions for your doctor. Always trust an in-person evaluation over any online tool — especially for chest pain, neurological symptoms, severe pain, high fever, or anything in pregnancy.
When you should always see a doctor
- Any symptom lasting longer than 2 weeks without improvement
- Symptoms that interfere with sleep, work, or daily function
- Unexplained weight loss, fever, or night sweats
- Changes in moles, new lumps, or bleeding
- Any mental-health symptoms with thoughts of self-harm
What an emergency really looks like
Some symptoms always justify calling 911 (or 999 / 112), even if you think you might be overreacting: chest pain or pressure that lasts more than a few minutes; sudden severe headache (“worst of your life”); weakness or numbness on one side of the body; difficulty speaking; vision loss; severe shortness of breath; severe bleeding; loss of consciousness; or thoughts of suicide. The cost of calling is small. The cost of not calling can be everything.
Important note
This tool is intentionally simple — it surfaces likely causes for common symptoms, not exhaustive differential diagnoses. It cannot replace the judgment of a clinician who can examine you, hear the full story, and order tests. Use it as a starting point for conversations, not as a verdict.