Detailed physical exam to evaluate for alternative diagnoses
Urinalysis and urine culture (typically patients will have a normal UA and sterile urine culture)
Sexually transmitted infection testing may be considered if patient is at risk for these
Postvoid residual
Cystoscopy may be considered
Diagnosis is made if the patient meets has “an unpleasant sensation (pain, pressure, discomfort) perceieved to be related to the urinary bladder, associated with lower urinary tract symptoms of more than 6 weeks duration, in the absence of infection or other identifiable causes”
Interstitial cystitis
Bladder, urethral, or genital tract cancer
Acute cystitis
Urinary Tract Infection 
Pyelonephritis
STI
Prostatitis
Benign pelvic mass