Legal Alcohol Limit in Louisiana: BAC Thresholds and DUI Penalties

The legal alcohol limit in Louisiana is a blood alcohol concentration of 0.08% for drivers age 21 and older. Commercial drivers are held to 0.04%, and anyone under 21 is limited to 0.02%. Reach or exceed the threshold that applies to you and the state can charge you with operating a vehicle while impaired, the offense most people call DUI or DWI. One detail sets Louisiana apart from many other states: there is no lookback period. A conviction from twenty years ago still counts as a prior when a court sentences you today.¹

The Three BAC Thresholds

For most drivers age 21 and over, 0.08% is the line. At or above it, you are legally impaired regardless of how you feel behind the wheel. The statute reaches beyond cars — it applies to anyone operating a motor vehicle, aircraft, watercraft, or other conveyance.²

Commercial driver’s license holders operate under a 0.04% limit. Federal rules apply that number whether you are on the clock in a truck or off duty in your personal car. The CDL follows you, not the vehicle.³

Drivers under 21 face a near-zero standard of 0.02%. A single drink can push a younger driver over that line. The underage offense is charged separately under RS 14:98.6, though a young driver who blows 0.08% or higher is prosecuted under the adult statute and faces the full adult penalty range.⁴

What Happens on a First Conviction

A first-offense conviction carries a fine of $300 to $1,000 and up to six months in jail. Most first-time offenders don’t serve the full jail term. Courts commonly suspend the remaining time in favor of probation, but probation comes with conditions.⁵

Those conditions include a court-approved substance abuse program, a driver improvement course, and either additional jail time or community service. The court also orders you not to drive for at least six months unless every vehicle you operate has an ignition interlock device installed.⁵

Separately, the Office of Motor Vehicles suspends your license for 12 months once it receives notice of the conviction. You can apply for a restricted license with an interlock device so you can still drive to work, school, and other approved destinations during the suspension.⁶

Second, Third, and Fourth Offenses

A second conviction carries a $750 to $1,000 fine and 30 days to six months in jail. At least 48 hours must be served without parole, probation, or suspension of sentence. Courts cannot waive that floor. The remaining time can be suspended only if you agree to serve at least 15 days in jail (or perform 240 hours of community service, half of it litter cleanup), complete a substance abuse program and driver improvement course, and use an interlock device for at least six months.¹

If the second arrest happens within one year of the first offense, at least 30 days must be served without parole, probation, or suspension.¹

Because Louisiana has no lookback window, a decades-old conviction still counts. The statute expressly applies “regardless of whether the second offense occurred before or after the first conviction.” If someone told you old DUIs “fall off” after ten years, that advice does not describe Louisiana law.¹

A third conviction is a felony. The fine is $2,000 plus a $100 assessment, and the sentence runs one to five years with or without hard labor. At least one year must be served without parole, probation, or suspension, and the mandatory minimum cannot be served on home incarceration except in narrow circumstances. The administrative license suspension jumps to three years, with a restricted-license option available after the first year if you install an interlock on every vehicle you drive.⁷

A fourth or subsequent conviction adds a $250 fine on top of the base fine, and at least three years of the prison sentence must be served without parole, probation, or suspension. This is felony territory that can carry decades of imprisonment.⁸

Higher Penalties Above 0.15% and 0.20%

Louisiana draws two additional lines above the base 0.08% threshold. Cross either and mandatory add-on penalties kick in that judges cannot waive.

On a first offense with a BAC of 0.15% or higher, at least 48 hours must be served in jail with no probation, suspension, or community service substitution available for that portion. The license suspension provisions under RS 32:414 also impose additional waiting periods before a restricted license becomes available.⁵⁶

On a second offense with a BAC of 0.15% or higher, at least 96 hours must be served without any sentence reduction, the license suspension extends to four years, and an ignition interlock device must remain installed and operational for that entire four-year period. If the BAC reached 0.20% or higher on a second offense, the fine rises to $1,000 and the same 96-hour minimum and four-year suspension and interlock requirements apply.¹

Refusing the Breath or Blood Test

By driving on Louisiana’s public roads, you have already given “implied consent” to submit to a chemical test — breath, blood, or urine — if an officer has reasonable grounds to believe you are impaired. You can still refuse, but refusing carries its own penalties that apply whether or not you are convicted of the underlying DUI.

A first refusal triggers an automatic one-year administrative license suspension. A second or subsequent refusal within ten years brings a two-year suspension. Those suspensions come from the Office of Motor Vehicles and run independently from any court-ordered penalty.⁹

Refusing also does not guarantee you’ll walk away from the DUI charge. Officers can still arrest and prosecute you based on field sobriety observations, dashcam footage, and other evidence. The U.S. Supreme Court has held that police may require a warrantless breath test as a search incident to arrest, though blood draws generally require a warrant or exigent circumstances.

Ignition Interlock Requirements and Cost

An ignition interlock device appears at every offense level. On a first offense, the court orders you not to drive for at least six months unless your vehicle has a working interlock installed. On a second offense, the interlock requirement runs at least six months and stays in place throughout any license suspension period. On a third offense, the device must remain until you complete substance abuse treatment and any home incarceration requirements.⁵¹⁷

You pay for the device. Installation typically runs $70 to $150, with monthly monitoring fees of $60 to $90 and calibration appointments every 30 to 60 days. Over a six-month minimum, most drivers spend $500 to $800. For a second offender with a high BAC facing a four-year interlock requirement, cumulative costs can reach several thousand dollars.

CDL Holders

Commercial drivers face steeper professional consequences than standard license holders. A first DUI conviction — in a commercial vehicle or a personal car — triggers a one-year CDL disqualification under federal regulations. If you were hauling hazardous materials at the time, that disqualification extends to three years. A second DUI-related conviction in a separate incident results in a lifetime CDL disqualification, and refusing a chemical test counts the same as a conviction for these purposes.¹⁰

For a truck driver or bus operator, a single conviction can end a career. The one-year bar is enough to lose most commercial driving jobs; a lifetime bar makes the loss permanent.

Costs Beyond the Fine

The statutory fine is the smallest line on the bill. After a conviction, auto insurance premiums increase substantially because insurers reclassify you as high risk, and that label sticks for years. Repeat convictions can make coverage extremely expensive or lead an insurer to drop you.

Louisiana generally requires proof of financial responsibility, often an SR-22 filing, before your driving privileges can be restored. The SR-22 isn’t insurance — it’s a certificate your insurer files with the state confirming you carry at least the minimum required coverage. It adds another layer of cost and paperwork to reinstatement.

Add fines, court costs, substance abuse program fees, driver improvement course fees, interlock installation and monitoring, higher premiums, and potential attorney fees, and a first-offense DUI can easily run several thousand dollars total. Repeat offenses multiply every one of those numbers.

Defenses Worth Raising

A charge isn’t a conviction. Several defenses come up regularly in Louisiana DUI cases.

The most common attacks the BAC test itself. Louisiana requires breath-testing instruments to undergo maintenance inspections at least once every four months, including calibration checks against a known alcohol value. If the equipment missed a scheduled inspection or the calibration fell outside tolerance, the results may be excluded.¹¹

Another defense challenges the stop. Under the Fourth Amendment an officer needs reasonable suspicion to pull you over and probable cause to arrest. If the stated reason for the stop doesn’t hold up, evidence gathered afterward may be excluded. The Louisiana Supreme Court applied this principle in State v. Waters, holding that a stop requires an objectively reasonable basis.¹²

Field sobriety tests are also open to challenge. They rely on the officer’s subjective observations and can be affected by medical conditions, uneven road surfaces, footwear, fatigue, and nervousness. A defense attorney will look closely at the officer’s training, the test conditions, and whether protocols were followed. None of these defenses guarantee dismissal, but any of them can reduce a charge or shift plea negotiations.

1
Louisiana State Legislature. Louisiana Code RS 14:98.2 – Operating While Impaired Second Offense Penalties
2
Louisiana State Legislature. Louisiana Code RS 14:98 – Operating a Vehicle While Impaired
3
Federal Motor Carrier Safety Administration. Is a Driver Disqualified for Driving a CMV While Off-Duty With a Blood Alcohol Concentration Over 0.04 Percent?
4
Louisiana State Legislature. Louisiana Code RS 14:98.6 – Underage Operating While Impaired
5
Louisiana State Legislature. Louisiana Code RS 14:98.1 – Operating While Impaired First Offense Penalties
6
Louisiana State Legislature. Louisiana Code RS 32:414 – Suspension and Revocation of Drivers Licenses
7
Louisiana State Legislature. Louisiana Code RS 14:98.3 – Operating While Impaired Third Offense Penalties
8
Louisiana State Legislature. Louisiana Code RS 14:98.4 – Operating While Impaired Fourth and Subsequent Offense Penalties
9
Louisiana Department of Public Safety and Corrections. Rights Relating to the Chemical Test for Impairment
10
eCFR. 49 CFR Part 383 Subpart D – Driver Disqualifications and Penalties
11
Cornell Law School. Louisiana Administrative Code Title 55 I-515 – Maintenance Inspection for the Intoxilyzer 5000
12
Justia. State of Louisiana v. Tony A. Waters