The Science of Blood Alcohol Content

The Science of Blood Alcohol Content


If you don’t care about the legal damage or danger posed to others by excessive drinking, at least understand the medical facts of what you’re doing. 

We’ve heard a lot in the news lately about how people are reluctant to put anything into their bodies when they don’t know the short and long-term possible implications of it. So isn’t it odd that as a society, we regularly, unquestioningly pour alcohol into our bodies with no real understanding of what it does? Would it make a difference even if we knew? Probably not since we’re well aware of the legal dangers it poses but keep behaving recklessly and needing an experienced St. Augustine DUI attorney anyway.   

If it sounds hypocritical, it’s because it is. So, for those of you who are big fans of “follow the science” and who are sincere about knowing what you put into your body does to you, here’s a more clinical dive than what many of our other blog posts have offered.

Blood alcohol levels, and thus, degrees of intoxication, are measured in gram%. The legal limit is 0.08 gram%, which means 0.08 grams of alcohol per 100 ml. 

The BAC Factors

How do you get to .08? There are a number of factors involved. And frankly, because there are so many factors and because every human body is different, it’s incredibly easy to misjudge or make wrong assumptions about how you handle your alcohol. Eventually, this translates into the inevitable “I’m fine to drive” statement you make to yourself right before you call us from jail.


Your Tolerance

How often you drink, how much you usually drink, and how long you’ve been drinking.


Not So Happy Bubbles

Love those rum & Cokes? Pretty much any carbonated drink can increase BAC. That’s because the carbonation causes alcohol to pass through the stomach and get into the blood faster.


Did You Eat?

It’s not some old wives’ tale. If you drink on an empty stomach, you’re going to have a higher BAC than someone who’s eaten. If there’s food in the stomach, it keeps the alcohol there longer (delaying emptying from the stomach into the duodenum) and slows its absorption into the bloodstream. And it’s not so much what you eat, it’s how much you eat (caloric content). Those beer nuts might not be enough. Food also stimulates the elimination of alcohol through the liver and increases elimination of ethanol from the blood.


Are You Stressed?

There aren’t very many good things about being stressed, but this is one of them. Stress tends to pull blood away from the stomach and small intestines and give priority to the muscles. As a result, alcohol doesn’t absorb into the bloodstream as fast. We do not recommend a lifestyle of high stress since that may be one of the things causing you to over-drink in the first place. 


How Old Are You?

There may be some truth to the little old lady who gets tipsy after drinking a little cooking sherry. Turns out it takes more to make a young person drunk than someone who’s older. We’ll let you decide what age qualifies as “old.” But if your body is telling you it can’t drink like it used to, listen to it. 



Sorry ladies. For a 150 lb. male, 4 ounces of spirits, four glasses of wine, or four beers will put him at a too-high 0.10 gram% BAC. For a female of the same weight, drinking these same amounts will take you to a 0.12. Two reasons. Body fat is distributed differently in males and females, with more fat per kilogram (and thus less water) for females. Also, females have lower gastric levels of alcohol dehydrogenase, an alcohol-metabolizing enzyme.


Do You Know Your Metabolism?

You’ve heard it a million times, probably in the context of ability to lose weight. Different people have different metabolisms. And it’s true. Metabolism is the rate at which foods and liquids are processed in the body. A slow metabolism will keep alcohol in the body longer and the liver will process it slower, meaning keeping a low BAC is going to be a problem.  


How Fast Are You Drinking? 

At least give your body a fighting chance. If you lightly sip on a drink throughout the night, your body can probably absorb and process that. If you guzzle one huge stein of beer after another, or worse yet, find yourself in a chugging contest, you’re flooding your body with alcohol that it’s going to need much more time to deal with. 


Are You Pumped?

Again, fatty tissue has a much harder time absorbing alcohol than muscles do. There are many “big” guys who like to think that because they’re big, they can handle a lot of intense drinking. Well, that depends. Are they big because of fat or are they big because they’re ripped? Those who are overweight see more alcohol left in the bloodstream until it can be handled by the liver. But be warned, tall and skinny people will reach a higher BAC than a musclebound counterpart as well.


How Much Alcohol is in Your Drinks?

Check out the alcohol content of various popular drinks 


Are You on Drugs? 

We’ve talked before about how prescription and over-the-counter medications can affect a breathalyzer test, creating a false positive. But some can also increase your BAC by affecting how alcohol is absorbed. For instance, if you’re currently taking cold and allergy pills, that’s going to intensify the effects of alcohol.


The Science of Measuring BAC


Authorities can get BAC measurements from any number of body fluid or tissue samples. Hopefully you’ll get tested using methods for people who are still alive. 


The standard is a blood test. That best represents the effects of alcohol on the brain. But tests can also be run using urine, saliva, sweat, and breath. How tests are conducted often have the potential to open a line of defense your St. Augustine DUI lawyer might use. 


Fun With Chemistry. How Alcohol is Metabolized


  • Alcohol is first metabolized to acetaldehyde by an enzyme called alcohol dehydrogenase.
  • Then that same vital aldehyde dehydrogenase breaks the alcohol down into acetate. 
  • Acetate then breaks down into carbon dioxide and water. 
  • If there’s a lot of alcohol, the liver enzyme CYP2E1 also kicks in to help.


How to Look Stupid. What Different BACs Do to You


0.01–0.04% You feel relaxed and kind of euphoric. You’re more social.

0.05–0.07% Now you’re starting to lose your inhibitions. You’re very friendly and talkative. For some, this is when motor skills start breaking down. Cognitive impairment is similar to having been awake 24 hours.

0.08% Your driving skills are (legally) impaired.

0.08–0.12% Driving is significantly impaired. You’re not so in control of your emotions anymore.

0.12–0.15% You’re staggering, and your speech is slurred. You can no longer trust your judgment. And you definitely can’t drive safely.

0.15–0.2% You’re obviously drunk to anyone looking at you, and your vision could be severely impaired.

0.2–0.3% You’re vomiting and not so in control of your bowels. You’re showing symptoms of alcohol intoxication.

0.3–0.4% You may be in a stupor and unable to move without help. It’s getting clear you have severe alcohol intoxication and it’s here that you could pass out/blackout.

0.4–0.5% You could go into a coma, possibly die.

Above 0.5% You’re much more likely to die because this is a fatal blood alcohol level.


Wait, What? Death?


Yes death. And here’s how it happens.


A high level of alcohol drops blood pressure, slows respiration, and lowers body temperature. But it’s what happens in the brain that creates the real problems. 


The respiratory center in the brain could cause respiratory paralysis and respiratory/cardiac arrest. 


Damage to the brain part that regulates the glottic reflex increases the likelihood of aspiration of gastric contents and asphyxia (and death). The major airways and lungs get inflamed from direct contact with noxious material and the trachea, bronchi and alveoli are damaged. This kind of acute lung injury releases proinflammatory cytokines and inflammatory cell infiltration. 


When you die from alcohol poisoning, the thing that eventually takes you out will be hypoxaemia. Google it. 


Your body frankly doesn’t care why you drink or take any of your excuses for drinking into consideration. It just does what it does because…medical science, biology, and chemistry. Your health is your business, and we aren’t doctors. But legal problems you run into as a result of being charged with DUI, we can help with that. Put the name and number of Shoemaker Law, 904-872-SHOE in your phone today.