BAC Law: Know the Consequences and Risks

Drinking and driving is not only dangerous; it is illegal. Knowing the BAC law in your local area can help you stay safe and keep you out of legal trouble.

In this article:

How is BAC Measured?

Blood alcohol concentration (BAC) refers to the percentage of alcohol in your bloodstream. For example, a BAC of 0.10 means that your blood contains one part alcohol for every 1,000 parts of blood.1 BAC typically is tested for medical or legal reasons.

Chemical tests measure the level of alcohol in your blood. One of the most common forms of testing is through a breathalyzer, which measures your BAC level by examining the alcohol present in your breath. While a breathalyzer gives fast results, it is not as accurate as blood tests.2

Healthcare professionals must administer blood alcohol tests. They use a small needle to take a blood sample from your arm to measure the alcohol present in your blood. Timing of the test affects its accuracy. Blood alcohol tests are only accurate within six to twelve hours of your last drink.2

Other chemical tests that may be administered are saliva or urine tests. In many states like New York, when you drive a motor vehicle, you are consenting to take a chemical test for intoxication.3

BAC law and legal alcohol limits can vary from state to state and country to country. Federal law in the United States sets the legal limit to drive a vehicle at 0.08 BAC.6 Most states have the same legal alcohol limits, except for Utah, which is just 0.05 BAC.7

According to a blood alcohol level chart of BAC law limits by country shared by the World Health Organization (WHO), the legal alcohol limits for driving are at or below 0.05 in many countries.8 In some countries, the limit is as low as 0.02, whereas others have a zero-tolerance policy and do not allow any alcohol consumption while driving. Legal alcohol limits often are lower for younger drivers and those driving commercial vehicles.8

Can I Refuse a Breathalyzer Test?

Refusing a breathalyzer test may have serious consequences. Most states have implied consent laws. This means you consent to taking a breathalyzer test every time you get behind the wheel.4

Many states have harsh penalties if you refuse a breathalyzer test, such as suspending your driver’s license. By refusing a breathalyzer test, you also could be admitting guilt in a court of law.4

Can Warrantless BAC Tests Be Admitted in a Court of Law?

Warrantless blood draws are deemed constitutional, barring exceptional circumstances, though their constitutionality is murky and subject to debate.5, 15 In cases of BAC and unconscious drivers, the time it would take to obtain a warrant could alter the evidence. BAC tests are time-sensitive because alcohol in the bloodstream decreases over time.

In situations where a driver is unconscious, or in a stupor and unable to give consent, the interpretation of the law offered in Mitchell v. Wisconsin enables police officers to order warrantless blood tests.15 This leaves a gray area in constitutional law because the 4th and 5th amendments of the U. S. Constitution function as protections against warrantless search or seizure and self-incrimination, respectively. A warrantless blood test seems to set limits on the 4th amendment or contextualize its application. Meanwhile, treating the refusal to take a blood test as admission of guilt seems to contradict the 5th amendment.

Ultimately, there is no clear-cut answer on whether a warrantless blood draw can be used as qualified evidence in a court of law.5, 15 The best approach is to know, understand, and uphold the local BAC law by obeying the limit and laws in your region.

The Advantages of Lowering Legal Alcohol Limits

The United States currently has one of the highest legal alcohol limits in the world at 0.08. Moreover, the National Transportation Safety Board (NTSB) issued a report in 2013, which recommended lowering the legal limit to 0.05. Still, it has yet to be changed even though several international studies have indicated that lowering the limit results in fewer alcohol-related fatalities.9

More research that supports a lower BAC law limit includes:8, 9

  • Lab studies show that most people are significantly impaired in critical driving functions at BAC levels of 0.05.
  • The relative risk of being involved in a fatal crash as a driver is four to six times higher for those with BAC levels between 0.05 and 0.07 than it is for drivers with no alcohol in their bloodstream.
  • A 2016 national survey indicated that 63.6% of American adult drivers support lowering the legal limit from 0.08 to 0.05.
  • According to research data and calculations, approximately 1,790 American lives would be saved if the legal limit were lowered to 0.05.

How BAC Law Works

Measuring BAC levels can help determine the level of intoxication in a person for medical and legal reasons.1 Most often, BAC levels are measured to determine if one is within the legal limit to drive safely. BAC levels can prove that a person is intoxicated but cannot prove that a person was driving if that was in question. However, it is a misconception that an officer needs to test your BAC level to arrest you. Police statements attesting that you appeared intoxicated are sometimes enough to charge you with driving under the influence (DUI).3

Increased Penalties for Higher BAC Levels

The higher your BAC level, the more dangerous it is to drive. For this reason, many states have enacted laws that enforce increased penalties for higher BAC levels.10

In 2014, 56% of intoxicated drivers involved in fatal crashes had BAC levels of 0.15 or higher.10 Most states that enforce higher penalties begin doing so at levels of 0.15 or higher, but some states such as Massachusetts do not enforce greater penalties until levels of 0.20 or higher.10

Zero-Tolerance Laws for Minors

BAC levels are also sometimes used to arrest minors for the consumption of alcohol. Many states have zero-tolerance laws with lower BAC limits for minors than the general population. Many states will remove driving privileges from minors caught driving with any amount of alcohol in their system. Other states may revoke driving privileges for any consumption of alcohol, whether the minor was driving at the time or not.1112

Receiving a DUI When You are Within the Legal Alcohol Limits

There may be situations when you can receive a DUI charge even if you are within the legal limit. This may happen under the following circumstances:3

  • You refused a chemical test, and the officer gave testimony that you appeared intoxicated
  • You are a minor under the age of 21
  • You were simultaneously under the influence of sedative medication, marijuana, or other illicit drugs

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Factors Impacting Blood Alcohol Concentration

Several factors can impact your blood alcohol content levels. BAC is primarily determined by how much you drink, how fast you drink, your body weight, and your gender from birth. But other factors can affect BAC levels as well.3

Unfortunately, there are many misconceptions regarding BAC levels, and it can be challenging for people to distinguish myths from reality. Below are some truths and falsehoods relating to factors that affect blood alcohol levels.

True or False?

Men can drink more than women and still have the same BAC.

True: Generally, men can drink more alcohol than women and be less intoxicated. This is because men generally are larger than women, have more body fat, and have more total body water content. However, while this statement is generally true, it is not always the case. Physiology is unique in each person regardless of gender, and many factors can affect BAC levels.12

The type of alcohol you drink can affect BAC levels.

True: Some drinks can intoxicate you quicker than others. Each alcoholic beverage is different in the alcohol content it contains. A standard drink is considered to be:2

  • One 12-ounce beer (4.5-6% alcohol)
  • One 5-ounce glass of wine (12% alcohol)
  • One 1.5-ounce shot of liquor (40% alcohol)

Hormones can affect BAC levels.

True: A menstrual cycle and estrogen levels can affect how a woman metabolizes alcohol. This means that the same amount of alcohol at different times in her cycle may affect her differently.12

Coffee and cold showers can lower your BAC level.

False: While coffee and cold showers may make you feel more alert, they do not sober you up. The only thing that can lower your BAC level is time.3

People who weigh more can handle more alcohol.

True: Generally, people who weigh more can drink more and not be as intoxicated as someone who weighs less because they have more room for alcohol to distribute throughout the body.2

Energy drinks can help you sober up and not be as intoxicated.

False: While energy drinks can help you feel more energized and alert, they will not lower your blood alcohol content or help you sober up faster.12

Eating while you drink can help lower your BAC levels.

True: Food slows down the absorption of alcohol in your bloodstream. The more food you have in your stomach, the longer it will take the alcohol to absorb, which can help prevent a spike in BAC levels. However, food cannot prevent intoxication if you have too much to drink.3

If you drink alcohol frequently and have a high tolerance, your BAC levels will not be as high as someone who drinks less often drinking the same amount.

False: Tolerance has no impact on blood alcohol levels. While you may feel less intoxicated or be able to drink more, your BAC levels remain the same.12

Medications can affect your BAC levels.

True: Certain medications can impact the way your body metabolizes alcohol. This could lead to higher BAC levels from less alcohol.2 For this reason, it is vital to talk to your doctor about drinking alcohol if you are taking certain medications.

In terms of BAC, it does not just matter how much you drink; it also matters how fast you drink.

True: Binge drinking raises blood alcohol content levels much faster than drinking at a slower pace. Binge drinking can be dangerous because it can raise BAC levels so rapidly that a person may not even recognize the signs of intoxication yet.12

If you use a BAC calculator to determine how many drinks you can have based on your gender and weight, you know that you are safe to drink that amount.

False: Everyone processes alcohol differently. While a BAC calculator and a blood alcohol level chart can provide helpful standards and guidelines, they are not always accurate due to the many factors that can affect how a person metabolizes alcohol. This includes enzyme production and levels in your body and the current condition of your liver.2 It is important to monitor yourself closely for signs of intoxication before deciding to drive. The best option is always to get a sober ride home.

Your Risks Increase with Your Blood Alcohol Levels

When your blood alcohol levels increase, not only do your legal risks increase, but so do your health risks. As your BAC levels increase, your risks of the following increase as well:13

  • Accident and injury
  • Experiencing or perpetrating acts of violence
  • Engaging in unprotected sex
  • Blackouts (gaps in memory while under the influence)
  • Loss of consciousness (passing out)
  • Alcohol poisoning (overdose)
  • Life-threatening misuse

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Signs of Alcohol Misuse: How to Know if You Need Professional Help

If you are getting intoxicated frequently or struggling to control your alcohol use, this may signify a medical condition called alcohol use disorder (AUD). AUD is characterized by an inability to stop or cut back on drinking despite harmful consequences to your personal, social, or professional life.14

If you answer yes to more than two of the following questions, you may qualify for a diagnosis of AUD. In the past year, have you:14

  • Wanted alcohol so badly that you could not think about anything else?
  • Spent a lot of time drinking or been sick from the after-effects of alcohol?
  • More than once wanted to cut back or stop drinking but been unable to do so?
  • Had to drink more alcohol than you used to to get the same effect or found that your typical number of drinks has less effect than previously?
  • Experienced times when you ended up drinking more or longer than you intended?
  • Continued to drink alcohol even if it was causing trouble with your family and friends?
  • Given up or cut back on meaningful activities that you enjoy because of your alcohol use?
  • Found that drinking or being sick from drinking kept you from fulfilling responsibilities at home, work, or school?
  • Experienced withdrawal symptoms such as irritability, insomnia, sweating, nausea, or seizures when you attempt to quit or cut back on drinking?
  • Continued to drink even if it made you feel depressed or anxious, making health problems worse, or causing memory blackouts?
  • More than once, engaged in risky behaviors that increase your risk of harm like unprotected sex, driving under the influence, or walking in dangerous areas?

Seeking Professional Help for Alcohol Use Disorder

If you or someone you love are struggling with symptoms of AUD, you are not alone. Call 800-948-8417 Who Answers? to talk to an addiction treatment specialist about alcohol addiction treatment and support group options near you.


  1. Stanford University. What is BAC?
  2. S. National Library of Medicine. (December 3, 2020). Blood Alcohol Level.
  3. New York State: Department of Motor Vehicles. Chapter 9: Alcohol and Other Drugs.
  4. Fussell, Brian Jr. (2020) Is There a Georgia Supreme Court, Problem? Analyzing the Georgia Supreme Court’s New Peculiar Approach Towards Breathalyzers and Implied Consent Law. Mercer Law Review: Vol. 71: No. 1, Article 22.
  5. Jackson, Jeffery. (2019, September 10). Warrantless Blood Tests and Unconscious Drivers–What United States vs Mitchell Does (and Doesn’t) Say. Washburn University School of Law.
  6. S. Department of Transportation. (September 19, 2019). Impaired Driving Laws, Enforcement, and Prevention.
  7. United States Department of Transportation. Drunk Driving.
  8. World Health Organization. (October 26, 2018). Legal BAC Limits by Country.
  9. Fell, J., & Scherer, M. (2018, December 1). Estimation of the Potential Effectiveness of Lowering Blood Alcohol Concentration (BAC) Limit for Driving from .08 to .05 per Deciliter in the United States. Alcoholism: Clinical and Experimental Research, 41(12): 2128-2139.
  10. National Conference of State Legislatures. (November 14, 2016). Increased Penalties for High Blood Alcohol Content.
  11. National Institute on Alcohol Abuse and Alcoholism: Alcohol Policy Information System. Underage Drinking.
  12. College of Saint Benedict. Understanding Blood Alcohol Content (BAC).
  13. National Institute on Alcohol Abuse and Alcoholism. (2021). Understanding the Dangers of Alcohol Overdose.
  14. National Institute on Alcohol Abuse and Alcoholism. (2021). Understanding Alcohol Use Disorder..
  15. Harvard Law Review. (2019). Mitchell v. Wisconsin Leading Case: 139 S. Ct. 2525. Harvard Law Review, 133(302).
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