Why do I keep swerving when I drive? Exploring the health factors behind poor control

October 1, 2025 •

5 min read

Statistics from the AAA Foundation for Traffic Safety estimate that drowsy driving, a leading cause of poor lane control, may cause hundreds of thousands of motor vehicle accidents each year. Understanding why you keep swerving when you drive is crucial for your safety and the well-being of others on the road.

Quick Summary

Investigating why you swerve while driving can uncover medical conditions like sleep apnea, vision problems, cognitive decline, or medication side effects. These factors can impair focus, reaction time, and coordination, leading to decreased vehicle control and increased accident risk.

Key Points

Underlying Health Conditions: Persistent swerving can be a symptom of various medical problems, including undiagnosed sleep apnea, vision impairment, and neurological conditions.
Medication Side Effects: Certain prescription and over-the-counter drugs can cause drowsiness or impaired coordination, significantly affecting your ability to drive safely.
Cognitive Impairment: Conditions like dementia and high levels of stress can affect judgment, attention, and decision-making, leading to poor lane control.
Professional Consultation: It is crucial to consult a doctor to identify the specific cause of your symptoms, review your medications, and get a proper eye exam.
Prioritizing Safety: If you experience repeated swerving, stop driving until a medical professional has determined the cause. You may need to rely on alternative transportation temporarily.
Lifestyle Factors: Simple changes like improving sleep hygiene and reducing in-car distractions can address some causes of poor vehicle control.

For most drivers, maintaining a straight path on the road is an automatic, subconscious action. However, when you notice yourself frequently drifting or involuntarily swerving, it's a significant warning sign that something is compromising your ability to drive safely. While mechanical issues with a vehicle can be responsible, many cases are linked to a range of underlying health factors that impair alertness, coordination, and judgment. Ignoring these signs can have serious consequences, making it vital to address the root cause promptly.

The Health Issues Behind Your Swerving

Sleep-Related Problems

Excessive daytime sleepiness is a major contributor to impaired driving, often causing drivers to drift or swerve without realizing it. The impact of fatigue on driving performance can be similar to that of alcohol impairment.

Sleep Apnea: This is a breathing-related sleep disorder where breathing briefly and repeatedly stops and starts. It causes interrupted sleep, leading to excessive daytime sleepiness and fatigue. Studies show people with untreated sleep apnea are at a significantly higher risk of motor vehicle crashes.
Sleep Deprivation and Shift Work: Chronic sleep deprivation or irregular sleep schedules, common in shift work, can severely impair alertness, reaction time, and concentration. Drivers with Shift Work Sleep Disorder (SWSD) are particularly vulnerable.

Vision Impairment

Clear and steady vision is fundamental for safe driving. Any degradation in your eyesight can directly impact your ability to maintain lane position.

Age-Related Changes: As we age, changes like decreased pupil size, presbyopia (difficulty with close-up focus), and cataracts can affect vision, especially at night. Poor night vision and increased glare sensitivity make it harder to perceive road markers and surrounding traffic.
Binocular Vision Dysfunction (BVD): This subtle eye misalignment can lead to dizziness or motorist disorientation syndrome while driving. This disconnect between what the eyes see and what the inner ear senses can cause unsteadiness and swerving.
Reduced Visual Field: Loss of peripheral vision, which can be caused by glaucoma, can significantly increase crash risk by limiting a driver's awareness of nearby obstacles or vehicles.

Medication Side Effects

Many prescription and over-the-counter (OTC) medications can affect driving ability by inducing side effects that interfere with motor control, awareness, and judgment.

Drowsiness and Dizziness: Medications like opioids, muscle relaxants, tranquilizers (benzodiazepines), some antidepressants, and many cold and allergy medicines can cause sedation. The FDA advises checking if it's safe to drive after starting or changing medication.
Impaired Coordination and Focus: Certain drugs can slow reaction times and impair motor skills, making it difficult to steer or brake effectively. This can cause slow or jerky steering, leading to swerving.

Neurological Conditions

Conditions affecting the nervous system can compromise the complex coordination required for driving.

Parkinson's Disease: This can lead to slow and imprecise movements (bradykinesia), cognitive decline, and increased reaction times, which all impair driving.
Epilepsy: Individuals with epilepsy who have uncontrolled seizures, or even subtle seizures or auras, may experience a temporary loss of awareness or control.
Multiple Sclerosis (MS) and Stroke: These conditions can cause fixed neurological deficits affecting motor function, coordination, and cognition, all of which directly impact driving ability.

Cognitive and Mental Health Factors

Dementia and Mild Cognitive Impairment (MCI): These progressive conditions compromise decision-making, judgment, and memory. Drivers with these conditions may make poor decisions, get lost, or become confused, leading to erratic driving. A lack of insight into their own impairment is a common and dangerous symptom.
Anxiety and Stress: Experiencing high anxiety or stress can lead to distraction and emotional agitation, pulling focus away from the road. Panic attacks or extreme nervousness behind the wheel can manifest as physical agitation and poor vehicle control.

Health-Related vs. Vehicle-Related Causes of Swerving: A Comparison


Cause Category	Example Causes	Driving Symptoms	Other Indicators
Health-Related	Sleep apnea, fatigue, medication side effects, cognitive decline, vision problems, anxiety.	Frequent, involuntary drifting across lanes; difficulty staying in the center of the lane; delayed or over-correction steering; swerving with no clear external trigger.	Excessive daytime sleepiness, headaches, impaired memory, blurred vision, dizziness, anxiety, or mental fog that exists outside of driving.
Vehicle-Related	Tire pressure issues, wheel misalignment, worn suspension components (e.g., shock absorbers), steering system problems.	Consistent pull to one side, especially when accelerating or braking; car feels loose or unstable; wobbling sensation at speed; steering wheel may not be centered.	Uneven tire wear, vehicle noise (e.g., rattling), poor handling on turns, worn-out feeling in the steering, issues with acceleration or braking performance.

What to Do If You're Experiencing Swerving

If you have noticed a pattern of swerving, it's essential to take immediate action to ensure your safety and the safety of others. While vehicle checks are important, addressing potential health issues is critical. Here are the steps you should take:

Stop driving immediately if you feel unwell or excessively drowsy. Pull over to a safe location and rest before continuing.
Schedule an appointment with your doctor. Explain your symptoms, mentioning that you have been swerving while driving. Provide a complete list of any prescription or over-the-counter medications you are taking.
Get a comprehensive eye exam. Many vision problems develop gradually and can be corrected with a new prescription or other treatments. Be sure to mention any issues with glare, night vision, or blurriness.
Discuss sleep concerns. If you feel excessively tired during the day or have symptoms like loud snoring, you may need a sleep study to diagnose or rule out conditions like sleep apnea.
Review your medications. Talk to your doctor or pharmacist about whether any of your medications could be affecting your driving ability. They may suggest an alternative or a different dosage.
Avoid distractions. Minimize in-car distractions like eating, using a phone, or adjusting the radio. Focusing on the road ahead and maintaining proper lane positioning can help if lapses in focus are the cause.
Consider a driving evaluation. An occupational therapist with specialty training can conduct a comprehensive assessment of your driving fitness, including on-road and off-road components, which can be especially helpful if a neurological or cognitive issue is suspected.

Conclusion

Swerving while driving should never be dismissed as a minor issue. It is a potentially life-threatening symptom that requires prompt attention, particularly when related to a medical or health-related cause. By consulting with your healthcare provider and taking proactive steps to address potential underlying issues like sleep disorders, vision problems, or medication side effects, you can significantly improve your safety behind the wheel. Prioritizing your health is the first and most critical step towards restoring your confidence and control on the road.

For more information on the dangers of drug-impaired driving, you can consult resources from the National Highway Traffic Safety Administration.

Frequently Asked Questions

Yes, high levels of stress or anxiety can significantly affect your driving. They can lead to mental distraction, emotional agitation, and a lack of focus, all of which can compromise your ability to maintain lane position and react appropriately to road conditions.

Sleep apnea causes repeated interruptions in breathing during sleep, leading to excessive daytime sleepiness and fatigue. This can cause you to become inattentive or even micro-sleep while driving, leading to unintentional lane drifting or swerving.

Be cautious with medications that cause drowsiness, dizziness, or impaired coordination. This includes opioids, muscle relaxants, tranquilizers (like benzodiazepines), certain antidepressants, and some cold and allergy medicines containing antihistamines.

Not always. While health issues are a common cause, swerving can also result from vehicle problems like low or uneven tire pressure, wheel misalignment, or worn-out suspension components. However, if you have ruled out mechanical issues, a medical cause is highly likely.

Yes. Vision problems like a gradual loss of peripheral vision, reduced night vision, or glare sensitivity can affect your driving without you immediately realizing it. A comprehensive eye exam is recommended to check for these subtle issues.

If a neurological condition is suspected, you should follow your doctor's advice carefully. This may involve further testing, medication adjustments, or, for your safety and the safety of others, stopping driving. Resources like driving evaluations with an occupational therapist can also be recommended.

The most important first step is to stop driving if you feel unsafe. Then, schedule an appointment with your primary care physician to discuss your symptoms and start the process of identifying the cause, which may involve referrals to other specialists.