When you should not get behind the wheel
You are not safe to drive if you are impaired by alcohol, drugs, or medication; if you have not slept in more than 18 hours; if you are experiencing chest pain, severe dizziness, or vision problems; or if you are emotionally overwhelmed to the point that you cannot concentrate. These are the conditions that most directly cause crashes and are within your control to prevent.
The question "Is it safe for me to drive?" is not about your record or your age or how many years you have been licensed. It is about your physical and mental state right now, in this moment, before you turn the key. If you cannot answer honestly that you are alert, sober, and able to focus on the road for the entire trip, the answer is no.
Key Takeaways
- Alcohol, drugs, and fatigue are the three most common reasons drivers cause crashes, and all are preventable by choosing not to drive.
- Prescription and over-the-counter medications can impair you even if they are legal and prescribed to you — check the label or call your pharmacist before driving.
- If you have a medical condition that causes sudden symptoms (chest pain, fainting, severe dizziness), you may need to stop driving temporarily or permanently until a doctor clears you.
- Emotional distress, anger, or panic can narrow your attention and slow your reaction time as much as alcohol does — waiting an hour or calling someone else is safer.
Alcohol and drugs: the clearest safety line
If you have consumed alcohol in the past few hours, you should not drive. The amount does not matter as much as the fact that alcohol impairs judgment, slows reaction time, and narrows your field of vision — all at levels you cannot feel. A person who feels fine to drive is often the person most impaired.
The same applies to marijuana, cocaine, methamphetamine, opioids, and other drugs. Many states now test for drug impairment the same way they test for alcohol, and the legal limit exists because below it, the risk is measurably higher. If you have used any substance in the past several hours, assume you are impaired and do not drive.
Prescription medications and over-the-counter drugs also impair driving. Antihistamines, sleep aids, pain relievers with codeine, anti-anxiety medications, and some blood pressure drugs all slow reaction time or cause drowsiness. The label may say "do not operate machinery," which includes a car. If you are unsure, call your pharmacist — they can tell you in one minute whether the medication you took this morning affects driving.
Fatigue and sleep deprivation
Driving while fatigued causes crashes at rates similar to driving under the influence. After 18 hours without sleep, your reaction time is as slow as it would be at a 0.05 blood alcohol level. After 24 hours, you are as impaired as someone at 0.10 — legally drunk in most states.
If you have been awake for more than 16 hours, you should not drive long distances. If you have been awake for more than 18 hours, you should not drive at all. This is not about feeling tired — it is about the fact that your brain cannot process information fast enough to avoid a crash, even if you think you are fine.
Night driving is riskier than day driving for everyone, but especially for people who are sleep-deprived. If you must drive after a long day, pull over every two hours, get out of the car, and walk around. If you feel yourself nodding off or missing exits, stop and sleep or call someone else to drive.
Medical conditions and sudden symptoms
Some medical conditions make driving unsafe without a doctor's clearance. If you have had a recent heart attack, stroke, or seizure, you should not drive until a cardiologist or neurologist says it is safe. The same applies if you have been diagnosed with a condition that causes sudden loss of consciousness, severe dizziness, or vision loss.
If you experience chest pain, severe shortness of breath, fainting, or vision changes while driving, pull over when ready and call 911. Do not try to drive yourself to a hospital. After any of these events, see a doctor before you drive again.
Some states require you to report certain medical conditions to the DMV, and some conditions can result in license suspension until you are cleared by a physician. Check your state's DMV website under "medical reporting" or "medical conditions" to see what applies to you. Your doctor can also tell you whether your condition affects your ability to drive safely.
Emotional and mental state
Anger, panic, severe anxiety, and grief all narrow your attention and slow your reaction time. If you are in an argument with someone, have just received bad news, or are so upset that you cannot think clearly, you should not drive. These emotional states are temporary, but the crash they cause is not.
If you are experiencing suicidal thoughts or a mental health crisis, do not drive. Call 988 (the Suicide and Crisis Lifeline) or text "HELLO" to 741741 (the Crisis Text Line). If you are in when ready danger, call 911.
Distraction from your phone, passengers, or your own thoughts has the same effect as impairment: it slows your reaction time and narrows your focus. If you cannot keep your attention on the road, you are not safe to drive.
Vision and hearing problems
If you cannot see clearly — whether because of cataracts, macular degeneration, uncorrected refractive error, or any other reason — you should not drive. Most states require vision of at least 20/40 to hold a license, and many require 20/30. If you are unsure about your vision, have an eye exam before you drive.
Hearing loss does not directly impair driving, but if you rely on sound to know where other vehicles are (sirens, horns, the sound of an approaching car), hearing loss can be a safety factor. More importantly, some hearing aids and cochlear implants can be distracting if they malfunction or feed back while you are driving. If your hearing device is not working properly, do not drive until it is fixed.
What to do if you are not safe to drive
If you realize you are not safe to drive, you have several options. Call a taxi or rideshare service. Ask a friend or family member to drive. Use public transportation. Wait until you are sober, rested, or calm enough to focus. None of these options is as inconvenient as a crash.
If you are at a bar or party and have been drinking, use a designated driver service or call a taxi before you drink. Do not wait until you are leaving to figure out how to get home. If you are too impaired to drive, you are too impaired to make good decisions about how to get home.
If you are taking a new medication, do not drive until you know how it affects you. Take it at home first, wait a few hours, and see whether it makes you drowsy, dizzy, or unable to concentrate. If it does, do not drive while you are taking it, or ask your doctor whether a different medication might work.
Frequently Asked Questions
How long after drinking alcohol is it safe to drive?
The general rule is one standard drink per hour, but this varies by body weight, food intake, and metabolism. A safer approach: if you have had any alcohol in the past two hours, do not drive. If you are unsure, use a rideshare service or call a taxi. The cost is far less than a crash or a DUI.
Can I drive if I am taking prescription pain medication?
It depends on the medication and the dose. Some pain relievers do not impair driving; others do. Check the label or call your pharmacist. If the label says "do not operate machinery" or "may cause drowsiness," do not drive. If you are unsure, ask your doctor or pharmacist before you take the medication.
What should I do if I feel dizzy or faint while driving?
Pull over to the side of the road as soon as it is safe to do so. Turn off the engine, get out of the car, and sit or lie down until the feeling passes. If it does not pass within a few minutes, call 911. Do not drive again until you have seen a doctor and know what caused the dizziness.
Is it safe to drive if I have not slept well the night before?
If you slept four to six hours, you are probably safe for short trips during the day. If you slept fewer than four hours, you should not drive long distances or at night. If you have not slept at all, do not drive. Fatigue impairs you as much as alcohol does, and you cannot feel it happening.
Can I drive if I am very angry or upset?
No. Anger and emotional distress narrow your attention and slow your reaction time. If you are too upset to think clearly, wait an hour, call someone to talk to, or ask someone else to drive. Your safety and the safety of others on the road depends on your ability to focus.