A "shy bladder" is when an employee cannot provide the required 45 mL of urine for a DOT drug test (49 CFR 40.193).

1. The collector discards the insufficient specimen (unless it was out of temperature range or shows signs of tampering) and starts the shy bladder procedure.
2. The employee may drink up to 40 ounces of fluid over a period of up to three hours while staying at the collection site.
3. If the employee still cannot provide enough urine, the collector stops the collection, and the DER arranges a medical evaluation within five days.
4. If the evaluating physician finds no medical condition that explains it, the MRO reports a refusal to test.

Leaving the site before the process is complete is a refusal.