Blood Alcohol Level

How is Blood Alcohol Level Calculated?

Drunk Driving has been a problem for a long time in the United States. Every year, thousands of people are killed in motor vehicle accidents that involve drunk driving.

Other words that most people are familiar with that relate to the problem of Drinking and Driving are DUI (Driving Under the Influence) and DWI (Driving While Intoxicated). In many states these two terms mean the same thing. They are used interchangeably. In some states DUI and DWI are used a little differently, but however they are used, DUI Penalties and consequences are a serious matter.

Blood Alcohol Concentration and its Effects

Minutes after consuming alcohol, it is absorbed into the bloodstream and the alcohol will accumulate in the blood (if the drinker’s liver is unable to oxidize it quickly enough). The liver can oxidize approximately one drink per hour. The alcohol which is not oxidized is distributed to different parts of the body and eventually reaches the brain. Alcohol absorption is a slow process and cannot be increased by exercise, cold showers or consuming coffee.

What does it mean if you have a blood alcohol concentration of 0.08%? It means that for every 10,000 drops of blood in your body, you have 8 drops of alcohol. Blood alcohol concentration can be affected by several factors including your body weight, the amount of alcohol you have consumed, your absorption rate, the amount of food you have eaten, your hydration levels, your age and your sex.

Chronic and heavy drinkers may damage virtually every organ in their body by consuming large amount of alcohol for extended periods of time. Liver damage is prevalent in alcoholics, because the liver oxidizes approximately 90% of the alcohol consumed. Alcoholism frequently leads to cirrhosis of the liver or hepatitis.


If you are stopped by the police and placed under arrest on DUI charges, two of the main things that will probably be used against you as evidence are breathalyzer and blood tests. Many people think that a breathalyzer and BAC (blood alcohol content) are the same thing. The truth is there is a very important difference. A breathalyzer does not read your BAC. A breathalyzer estimates it.

You may ask, “What exactly is a breathalyzer?” It is a breath analyzer. A breathalyzer is a device that is used to estimate your (BAC) from a breath sample. Breathalyzers can detect and measure your current alcohol levels. You blow into a breathalyzer and the results are given as a number. This is known as the Blood Alcohol Concentration (BAC). This shows the level of alcohol in your blood at the time the test is taken. (Check out our BAC Calculator for a demonstration of how BAC works.)

Breathalyzer Testing Problems

It is extremely important to remember that a breathalyzer estimates rather than reads your BAC. You may ask, “But what does this difference really mean to me and my DUI arrest?” This means that breathalyzer test results are far from being 100% certain and can often be challenged in court.

There are several problems with breathalyzers that can result in an inaccurate estimation of your BAC. Some of these are:

  • Breathalyzers assume a specific ratio between BAC and breath alcohol content in order to make their estimations. This is a 2100:1 ratio. However, this ratio may actually range between 1700:1 and 2400:1. This variation could make a huge difference in your case. For example, if the breathalyzer estimates your BAC at 0.08% then your true BAC could vary between 0.065% (legal) and 0.09% (illegal). If your BAC was 0.065%, proof of impairment would be needed.
  • BAC levels can be affected by physical activity. There was a study that showed running up and down the stairs right before a breath test could decrease your BAC up to 25%.
  • Breathalyzer machines can be confused by other substances which lead to an inaccurate estimation of your BAC. Examples of this are acetone, adhesives and paint.

It is interesting to note that urine tests also make estimations on an assumed ratio of 1.3:1. This is a ratio that may not apply to every person.

Defending Against The Breathalyzer

So, what does this mean to you if you are facing DUI Charges? If your DUI arrest was made and your DUI charges issued based on a breathalyzer or urine test, a good DUI Lawyer may be able to help you challenge the results of these tests.

The other main evidence that will probably be used against you for DUI charges is blood tests. Blood tests are the most accurate method of determining your BAC. This usually involves blood being drawn from you by a doctor or other qualified medical professional. This is typically done when you are taken to the police station after a DUI Arrest.

Once again, there are three ways of determining your blood alcohol content (BAC). These are by breath (breathalyzer), urine or blood tests. The most accurate is a blood test. The least accurate is a urine test. Thus, if you are given a choice as to which test you would like to take, a blood test is probably the wisest choice if you are sure that you are sober. A urine test, which as the least accurate is easiest to challenge, would be the right choice if you believe your BAC is above the legal limit.

DUI Lawyer

Facing DUI charges and DUI Penalties is a serious matter. Your DUI defense is not something that you can handle by yourself. You are going to need the help of an attorney.

Who is the right attorney for you? Choosing the right DUI Lawyer may be one of the most important decisions you will ever make. General or family attorneys are great, but are they the right ones in this type of case?

You need a lawyer who handles drunk driving cases. You need a DUI lawyer who specializes in this type of case.

A determined DUI Attorney may be able to minimize the fines and damages you face. An established DUI lawyer may even be able to have the DUI charges against you dropped.

The penalties and consequences of a DUI arrest and conviction can last for the rest of your life. You are going to need a DUI Defense that is provided by a DUI lawyer who knows and is experienced in dealing with DUI charges, DUI laws and DUI penalties and consequences.

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