Anxiety, and all its attendant symptoms, can last however long you perpetuate it.
Here are a list of behaviors that will keep you locked in the anxiety cycle:
Going to the doctor
Getting a medical test
Running to Google to look up symptoms
Interpreting your symptom as negative, dangerous, or the sign of a serious disease/disorder
Worrying about your disease
Coming on here and asking for reassurance
There are others. But basically, our bodies become symptomatic when our stress levels are high enough to become reactive. Again, you may not **FEEL** anxious, but your central nervous system can still be overtaxed. Period. Incidentally, your body can't tell the difference between real and perceived danger, so even if you worry about something as innocuous as dizziness, you're triggering the same response as if you were getting chased by a bear.
The best thing we can do for ourselves as anxiety sufferers is to try and refrain from interpreting our symptoms as harbingers of doom. When we do that, we keep our CNSs ramped up and give our bodies no time to relax, which then simply perpetuate the symptom/fear/symptom cycle. Hard to break? You betcha. But very necessary when it comes to true recovery.