How i know if my back ache is dangerous?

Good question: This is a very good question and it is not easy to answer. The best way to answer is to see a doctor. Some concepts to consider- 1) serious back aches interfere with walking, sensation to touch, or control of the urinary or bowel function 2) serious back aches occur with trauma, a history of cancer, or infection 3) serious back aches tend to become rapidly worse Hope that helps!