{"id":286635,"date":"2016-04-04T10:45:05","date_gmt":"2016-04-04T15:45:05","guid":{"rendered":"https:\/\/content.findlaw-admin.com\/ability-law\/dui\/arrests\/bac-test-faqs.html"},"modified":"2026-04-06T16:18:33","modified_gmt":"2026-04-06T21:18:33","slug":"bac-test-faqs","status":"publish","type":"page","link":"https:\/\/www.findlaw.com\/dui\/arrests\/bac-test-faqs.html","title":{"rendered":"How the Police Test BAC: FAQ"},"content":{"rendered":"\n
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How the Police Test BAC: FAQ<\/h1>\n\n
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\n By Lark Lewis, J.D.<\/a> | Legally reviewed by Melissa Bender, Esq.<\/a>\n | Last updated\n
\n \n <\/i>\n Legally Reviewed\n <\/summary>\n\n
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This article has been written and reviewed for legal accuracy, clarity, and style by FindLaw\u2019s team of legal writers and attorneys<\/a> and in accordance with our editorial standards<\/a>.<\/em><\/p>\n\n <\/div>\n <\/details>\n\n

\n \n <\/i>\n Fact-Checked\n <\/summary>\n\n
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The last updated date refers to the last time this article was reviewed by FindLaw or one of our contributing authors<\/a>. We make every effort to keep our articles updated. For information regarding a specific legal issue affecting you, please contact an attorney in your area<\/a>.<\/em><\/p>\n\n <\/div>\n <\/details>\n<\/section>\n\n\n

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Key Takeaways<\/h2>\n

Blood alcohol concentration<\/span> (BAC<\/span>) tests measure the amount of alcohol<\/span> in your blood. But they aren\u2019t always actual blood tests<\/span>. Breath testing<\/span> is more common. These tests help the police determine whether you\u2019re driving under the influence<\/span> (DUI<\/span>).<\/p>\n\n <\/div>\n <\/div>\n<\/div>\n\n\n

At a traffic stop<\/span>, law enforcement<\/span> officers<\/span> might use field sobriety tests<\/span>. These tests can give them some indication as to whether you\u2019re impaired. But they don\u2019t measure your exact level of impairment<\/span>. That\u2019s where BAC<\/span> tests<\/span> come in handy.<\/p>\n

This article answers frequently asked questions about BAC<\/span> tests<\/span>. It explains the methods used to measure blood alcohol levels<\/span> and how Breathalyzer tests<\/span> work. You\u2019ll also learn about the accuracy of BAC<\/span> tests<\/span> and whether it\u2019s possible to challenge Breathalyzer results in court.<\/p>\n

If a police test shows you\u2019re over the legal limit<\/span> for alcohol, you\u2019ll face an arrest for driving while intoxicated (DWI<\/span>). This is when the advice of a nearby DUI<\/span> lawyer<\/span><\/a> can be valuable. Get help for a DUI<\/span> case<\/span> promptly.<\/p>\n

What methods are used to measure blood alcohol concentration<\/span> (BAC<\/span>)?<\/h2>\n

Your blood alcohol content<\/span> can be measured in multiple ways. The police can use limited types of BAC<\/span> tests<\/span> at a traffic stop<\/span>. More advanced tests are available at the police station<\/span> after they bring in a driver suspected of drunk driving<\/span>.<\/p>\n

To estimate your blood alcohol concentration<\/span>, police can use samples of:<\/p>\n