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Understanding Blood Alcohol Level (BAC)

John Schaffer, LPCC

Medically reviewed by

John Schaffer, LPCC

February 25, 2019

Blood alcohol level is the measurement that determines the percentage of alcohol in an individual’s blood. The legal limit that a person can be at is .08 percent, anything above this causes the senses and abilities to perform common tasks to be greatly impaired.

Imagine this: You’ve been out to the bar for a couple of hours. After having a few drinks of wine and finishing them off with some shots, you realize that it is getting late and need to get going. Since your new boss has stepped into her position, work days are daunting, and you can use all the relaxation and rest you need: Drinks and sleep. Thankfully, your house is only a few miles away from the nearest watering hole.

On the way home you spot the headlights of vehicle approaching. It’s getting abnormally close. The next moment, lights are flashing, and realization hits: You’re being pulled over by what appears to be a county police vehicle.

Although you felt fine when leaving the bar, once talking to the officer, your senses seem foggy. You know that a sobriety test and breathalyzer are about to take place, and it’s not going to be good. You don’t even want to know your blood alcohol level.

Later, in the back of the cop car, you wonder: What exactly is blood alcohol level, and how is it accurately determined?

Blood Alcohol Concentration

People often refer to Blood Alcohol Concentration (BAC) as blood alcohol level. However, both forms of terminology have the same meaning: The amount of alcohol that is present in a person’s blood.

BAC is measured by the weight of alcohol per unit of volume of blood. This measurement is converted to a percentage form, such as 0.10 percent. In this example, a person’s blood would contain an alcohol level of one-tenth of a percent.

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Legal Limits

In order to drive in the United States, a person’s BAC must be under a certain percentage: 0.08 percent. Research has shown that once Blood Alcohol Concentration reaches .09 percent or higher, senses and ability to respond in common tasks (such as driving) are greatly hindered.

Since one of the ways that alcohol is released from the body is through breath, a breathalyzer can accurately determine the concentration of alcohol in a person’s blood.

How Alcohol Affects The Human Body

When a person drinks alcohol, it is absorbed into the bloodstream. Booze quickly affects many bodily functions:

  • Frequent Urination: The body recognizes alcohol as a toxin and tries to eliminate it from the system through urination.
  • Brain: Functions of the brain are inhibited when drinking.
    • This is why a person starts to behave differently, sometimes becoming more outgoing, forthcoming, and inappropriate.
    • Higher-order thinking is affected, and the abilities to make good decisions and effectively process information are limited.
    • Alcohol also affects the part of the brain associated with memory and emotion, causing exaggerated emotions and fragmentation of memories.
    • Coordination and movement are negatively affected, causing slurs in speech and disruptions in balance.
  • Liver: The liver attempts to remove alcohol from the body, which is recognized as a poison. A hard drinker’s liver can be damaged over time, causing Alcoholic Liver Disease.
  • Pancreas: When drinking, the pancreas secretes enzymes internally. Eventually this causes inflammation and can lead to pancreatitis.
  • Kidneys: Excessive consumption of alcohol can cause high blood pressure, which is the leading causing of kidney failure. Drinking alcohol also disrupts the kidney’s ability to efficiently balance the body’s fluids.

What This Means For A Person With Alcohol Dependency

It’s sometimes difficult to fully comprehend all of the ways that drinking too much alcohol wreaks havoc on the body. However, the effects of alcoholism are undeniable. A person who abuses alcohol:

  • Has a greater risk for cancer
  • Can suffer from alcohol poisoning
  • May become diabetic
  • Might have sleep disruptions
  • Can suffer from depression

In other words, a person dealing with dependency on alcohol has many mental, emotional, and physical health concerns to consider.

Get Yourself Back On Track

If you know someone who has been struggling with drinking too much, then you have probably recognized some of these signs or symptoms. The ways that alcoholism affects the health of a person can be shocking. This is why a person dealing with alcohol abuse needs opportunity for rehabilitation and recovery. Alcoholism is a challenge that should be addressed through quality treatment.

You or a loved one deserves to get help. Contact us right away at to speak with a professional about options that are available to start the process of detoxification in rehab.

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