What Causes Frequent Unquenchable Thirst For Cold Liquid With Frequent Urination?

I have been having frequent unquenchable thirst for cold water or cold beverage, rarely urinary retention after drinking water, but more often than not, always followed by intense frequency urination, dry mouth, deep sighing. My spidey sense is a viral basis that's affected the hypothalamus. What tests do I request from my doctor to rule out diabetes insipidus? And can I ask for a regular x-ray for thymus?