I realize that this is not an option with reference to breathalyzer tests with Pilots (I have had a couple myself) but as far as driving is concerned there is a blood test option in many states in the US.
In fact, in Florida the advice given to motorists concerned they may be over the limit when stopped by the Police is 'if you don't know, don't blow'
As mentioned, it is your option to have a blood test, if you are borderline close to the limit by the time they get you to a hospital or clinic and find someone to administer a blood test you may very well be legal.
Not endorsing drunk driving at, just thought I would point this out. Is this an option for a motorist in the UK ?