How Is Blood Alcohol Concentration (BAC) Measured?

Blood alcohol concentration, or BAC for short, is an essential metric for establishing whether someone was drunk driving or not (or even otherwise inebriated). The police can ask a suspected drunk driver to submit to a Breathalyzer test, followed by other sobriety tests, if needed, to ascertain if they are inebriated.

If you are facing DUI charges, don’t hesitate to contact a qualified criminal defense attorney in Spartanburg, South Carolina, from the Bateman Law Firm, for help. We can help you build a strong defense against the charges and ensure the best possible favorable outcome.

However, this article will discuss how BAC is measured and why it matters to you.

What Is The Definition Of Blood Alcohol Concentration (BAC)?

The amount of alcohol in your blood is measured by your BAC, or blood alcohol concentration. It is calculated by dividing the weight of the alcohol in grams by the volume of blood in liters. For example, a BAC of 0.05% indicates that you have 0.05 grams of alcohol in every 100 mL of blood.

The legal limit for BAC varies by country, but it is usually between 0.05% and 0.08% (the latter is true for most of the USA states, including South Carolina). If your BAC exceeds the legal limit, you are considered impaired and may face fines or other penalties.

There are several ways to measure your BAC, these include breathalyzers, urine tests, and blood tests. The most accurate way to measure your BAC is with a blood test, but this is only sometimes practical or possible.

Many factors can affect your BAC, including your weight, gender, how much alcohol you’ve consumed, and how fast you were drinking it.

Ways To Measure BAC

No matter which method is selected for measuring your BAC, some factors will affect the outcome. First, your BAC will change over time as your body metabolizes the alcohol. If a measurement is taken immediately after drinking, your BAC will be higher than an hour or two later.

Second, different people metabolize alcohol differently. This means that two people with the same BAC could have very different levels of intoxication.

Here are some of the most common ways to measure BAC.

Breathalyzer Test

First up is the breathalyzer test. A breathalyzer test measures the amount of alcohol in your breath and then uses that number to estimate your BAC. This test is the most common way to measure BAC and is typically used by law enforcement officers when pulling someone over on suspicion of DUI/DWI.

if you are pulled over for DUI, the police will check your BAC

Urine Test

Urine tests can also measure BAC but are less accurate than breathalyzers or blood tests. They are sometimes used as a preliminary test before administering a more accurate test, such as a blood test.

Blood Test

Another less common way to measure BAC is through a blood test. A blood test can be more accurate than a breathalyzer test but is also more invasive and expensive. This is typically performed in a hospital or medical facility.


The last method (and the least practical one in drunk driving cases) is to mathematically calculate the BAC based on how much alcohol you’ve consumed and how long it’s been since you’ve drunk. This method is less accurate but can be used without a breathalyzer or blood test.

The Breathalyzer test is the most commonly used method and is the most relevant one too when it comes to establishing bases for drunk driving charges.

How Does Age, Weight, And Gender Affect BAC Levels?

Age, weight, and gender can all affect blood alcohol concentration (BAC) levels. Generally, the older a person is, the more slowly their body metabolizes alcohol. This means that older people may have higher BAC levels than younger people after drinking the same amount of alcohol.

Similarly, people who are overweight or obese may also have higher BAC levels because alcohol is not metabolized as quickly in individuals with more body fat. Gender can also affect BAC levels; women generally have higher BAC levels than men after drinking the same amount of alcohol due to differences in metabolism and body composition.

Legal Implications Of High BAC Levels

In most states, including South Carolina, it is illegal to drive with a blood alcohol concentration (BAC) level of .08% or higher. If caught driving with a BAC above the legal limit, you could be facing serious penalties, including jail time, fines, and the loss of your driver’s license. In some states, you may also be required to install an ignition interlock device in your vehicle.

If you are involved in a car accident while under the influence of alcohol, you could be liable for any property damage or injuries that occur as a result. You may also be sued by the other party involved in the accident. If someone is killed due to the accident, you could be charged with vehicular homicide.

It is important to note that even if your BAC is below the legal limit, you can still be charged with driving under the influence (DUI) if your ability to operate a vehicle is impaired by alcohol. If convicted of DUI in such a case, you will face similar penalties as if your BAC was over the legal limit.

If you’re facing charges for driving with a high BAC level, it is important to seek legal help immediately. An experienced criminal defense attorney in Spartanburg, South Carolina will know how to best defend against these charges and help you avoid severe penalties.

Seek Help From A Qualified Criminal Defense Attorney In Spartanburg, South Carolina

If you are facing DUI charges in Spartanburg, South Carolina, it is important to get legal support from the best DUI lawyer in Spartanburg, South Carolina as soon as possible. A DUI conviction can result in significant penalties, including jail time, fines, and losing your driver’s license.

Our experienced attorneys, at the Bateman Law Firm, will review your case’s facts and help you build a strong defense, ensuring the best (or the least severe) outcome.

Don’t drink and drive, but if you do, don’t waste any time making an already bad situation worse; contact us immediately to get started on your legal defense!