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Driving With Hypothyroidism: Worse Than Driving Drunk?

Hypothyroidism Affects Driving

Those who suffer from hypothyroidism are likely familiar with a number of bodily impediments including fatigue, reduced nervous system functionality, and hindered cognitive ability. However, there may be a more prominent and dangerous effect that accompanies underactive thyroid. Impaired driving.

In a study presented at a conference of the International Society of Endocrinology and the Endocrine Society ICE/ENDO 2014, located in Chicago, an investigation was conducted regarding the effects of hypothyroidism on mental faculties. Kenneth Ain, MD, of the University of Kentucky and the Veterans Affairs Medical Center in Lexington, KY, stated that, at the time, no studies had been conducted which examined the specific changes that take place in hypothyroidism. With this study, Ain has shown that hypothyroidism may indeed be connected to reduced driving ability.

The study consisted of 32 patients previously diagnosed with thyroid cancer. These individuals were in process of ceasing their thyroid treatments in preparation for radioactive iodine scanning. Because of this situation, researchers were able to conduct tests while patients were actively taking thyroid hormone, during a period of no medication, and once again when they returned to prescribed thyroid hormone therapy. Interestingly, after returning to a regulated and balanced thyroid hormone dosage, driving impairment was no longer an issue for the participants.

In addition to a large array of neurological and psychological tests, which commonly returned data pointing to depression and reduced neurological function, patients underwent simulated driving tests. Interestingly, these mental states correlated to reduced braking speed in the driving simulations that were similar to cases where individuals had blood alcohol levels of 0.082 g/100 mL. The data shows that those who were diagnosed with and were continuing treatment for hypothyroidism were driving as impaired as those whose blood alcohol was above the U.S. legal limit.

As made clear with this data, those with sever hypothyroidism may experience impaired driving that is equivalent to driving while intoxicated. Co-author of the study, Charles Smith MD, of the University of Kentucky, suggests that physicians inform their patients of the possible dangers associated with hypothyroidism in regards to driving as well as asking them to refrain from driving until appropriate treatment is administered.

What Does this Mean for People with Hypothyroidism?

In general, those who have a mild to moderate condition of hypothyroidism should not have to worry about driving impediment. Because this study was conducted on those with thyroid cancer, it is likely that they had their thyroid glands removed. Meaning that they are more prone to having heightened levels of TSH (thyroid stimulating hormone), experiencing spikes upwards of 20.0 to 30.0 or even higher. However, those without severe thyroid conditions would likely not see a number shift of that degree in brief periods.

That being said, if you do recognize severe symptoms you should be cautious about your driving habits and perhaps even refrain from driving until you, along with assistance from your physician, maintain a proper thyroid balance. If you experience an inability to concentrate as well as slowed reflexes and response times, do not drive until your thyroid condition is consistently controlled. Through effective treatment and regular management of one’s condition, driving ability should remain unaffected.

Do I have Hypothyroidism?

Although difficulty driving may only be present in cases of severe hypothyroidism it is important to recognize symptoms of a thyroid condition. In the Colorado Thyroid Prevalence Study of 2000, it was shown that roughly 10% of the study group was not correctly diagnosed with hypothyroidism even though they did indeed have it. This study shows that a large number of the population may in fact not be safe behind the wheel of a car and not even be aware of it. In order to keep a mild thyroid condition from turning into a critical one, recognition from the individual and input from a medical professional is of great importance.

As is the case with most thyroid conditions, hypothyroidism can occur in varying degrees. Dependent on the severity of the condition one can have few or nearly all of the following symptoms with differing levels of intensity.

  • Fatigue
  • Sensitivity to Cold
  • Dry Skin
  • Weight Gain
  • Muscle Weakness
  • Muscle Aches
  • Pain, stiffness, and swelling of joints
  • Hair loss
  • Depression
  • Heavier or irregular menstrual cycles
  • Impaired memory

If left unchecked and allowed to progress, hypothyroidism in its advanced state can become myxedema. Some ways to recognize this include reduced breathing, low blood pressure, lowered body temperature, unresponsiveness, and in some cases, coma. This possibly life threatening condition is easier to combat when recognized early. When acted upon, knowledge pertaining to your thyroid and what symptoms manifest could greatly inform your physician and better equip them in helping you.

Understanding A Thyroid Condition

In light of this new study providing connections between hypothyroid symptoms leading to impaired driving ability it is now more important to properly diagnose and treat thyroid conditions. The Colorado Thyroid Prevalence Study also showed that 40% of the sample population fell outside standard reference ranges of TSH.

It is recommended for those who feel they may have a thyroid condition to consult a physician as well as educate themselves about the thyroid and how to care for it. Understanding one’s individual thyroid condition is important because each one is unique. Even though symptoms may be mild, early recognition, a comprehensive understanding, and proper treatment could relieve a great deal of bodily stress now and prevent further damage in the future.

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AlessandraMichelle Recent comment authors
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Having experienced this myself during January while the heater in the car was faulty, I can fully agree with the effects of drowsiness, response time, concentration & coordination. Only ever prescribed Levothyroxine from the NHS & annually tested in March doesn’t cover ant ”thyroid storms” that Hashimoto’s patients experience. The highs & low of this condition have been misdiagnosed as Bi-Polar Disorder in myself & many others & psychiatrists so sure that they have the right diagnosis, they go ahead & prescribe Sodium Valproate & Lamotrigine, further effecting cognition, concentration etc. Coroners report will read Accidental Death.


My test results are usually below range hypo, because current primary and last three endocrinologists only go by TSH, which causes my t3&t4 to tank. I haven’t driven a car in nearly sixteen years and I don’t want to drive, everything stresses me out. I’ve been on Social Security Disability since September 2003 for Chronic Clinical Depression and severe Anxiety Panic Disorder. I’d like to find a doctor in Chicago that would medicate me to optimal but finances are an issue. I can’t afford $299 a pop until I find the correct doctor for me, previous experience indicates it will… Read more »

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