My white blood cells are 17500. what exactly does that mean?

Get it worked up,,: This can be an infection in your body somewhere, but it might be something else. If it is infectious in nature, you would likely have other symptoms like fever and chills and a general feeling of malaise or being tired. Otherwise, a possible blood disorder should be ruled out. The first best step is to see your doctor for an initial work-up/evaluation to get an accurate idea. Best of luck.