By driving a motor vehicle in Arizona, you give your "implied consent" to submit to a chemical test for alcohol or drug content if suspected by a police officer of driving under the influence. The officer gets to decide which test he/she wants to request, and if you refuse, you will lose your license. The test is usually of either breath or blood, but can be other bodily substances as well.
If you refuse to take a test, the prosecutor can later argue that you refused out of a "consciousness of guilt." If you refuse to take a test, the officer can still obtain chemical evidence from you by obtaining a search warrant. When the cops get a warrant during a DUI arrest, they almost always will force you to take a blood test. This is because it would be very difficult to force somebody to blow into a tube. With a search warrant, they can strap you down and forcibly take your blood.
There is much confusion surrounding whether it is best to take a test or to refuse the test. There is also much confusion as to when to submit to the test. For a first time DUI arrest, it is usually best to take a test. This is because the punishments for taking and failing a test are usually less than refusing the test. If you refuse (and it's your first DUI) you will lose your license for one year. If you fail the test (i.e., it reads above a 0.08), you will lose your license for a maximum of 90 days from the MVD. This must be weighed against the possible criminal punishments for refusing versus taking the test. If it is your first DUI and you register above a 0.08, but under a 0.150, you are eligible for the minimum DUI punishment available in Arizona (AZ). However, if you register a BAC of 0.150 or above, you may be convicted of "extreme DUI," which carries a stiffer jail sentence than you would necessarily get had you refused and been convicted of an "affected by" DUI.
When Arizona (AZ) DUI law talks about "Alcohol Content" or BAC, it refers to the number of grams of alcohol present per 100 milliliters of blood in the person's system. A BAC of 0.10 would mean that the person has 1/10 of a gram of alcohol per every 100 milliliters of blood. So when it comes to the legal limit of 0.08, we are not talking about a whole lot of measurable alcohol.