Suddenly Feeling Lightheaded? Here Are Likely Reasons Why

Most everyone has had the experience of feeling lightheaded on occasion. Sometimes it registers as just a passing moment of dizziness. Other times it can feel as if you're about to pass out. But what is really behind that sudden weightless feeling? Why does it occur in the first place?

A feeling of lightheadedness can be triggered by a variety of causes, explains Gregg Fonarow, MD, director of the Ahmanson-University of California Los Angeles Cardiomyopathy Center. "It can occur if there are circumstances limiting blood flow to the brain, but also for other reasons," he says.

"Causes for lightheadedness include dehydration, excessive heat exposure, prolonged standing, excess physical exertion, standing up too quickly, very slow or very fast heart rates, low blood pressure from medications or abnormalities in the autonomic nervous system."

Dr. Fonarow adds, "Valvular heart disease, like aortic stenosis, may also cause lightheadedness." But so can anxiety and hyperventilation. And, at its most serious, "lightheadedness may be a sign of heart attack or stroke," he warns.

Read more: What Should You Eat or Drink When You Feel Lightheaded?

According to the American Heart Association (AHA), in addition to the classic symptoms of chest discomfort and shortness of breath, one possible though perhaps surprising sign of a heart attack is a feeling of lightheadedness.

How can that be? Heart attacks can occur when the arteries that carry blood to the heart muscle narrow over time due to a buildup of plaque, a condition called atherosclerosis, says the AHA. Arteries can become so narrowed from plaque deposits that the flow of blood is reduced or even stopped.

Equally dangerous, pieces of plaque can break off and become lodged in an artery, completely blocking blood flow, the AHA explains. Depending on the artery involved, you can suffer a heart attack. The plummeting blood flow starves both the heart and other organs of needed oxygen, and that can cause a feeling of lightheadedness.

The AHA adds that dizziness and lightheadedness can also be symptoms of an extended irregular heartbeat, called an arrhythmia.

Read more: Post-Workout Lightheadedness

Inner ear problems can cause strange sensations, but rather than lightheadedness, the sensations are more often a feeling of weightlessness, which is usually associated with vertigo. However, it may be hard for you to tell the difference between weightlessness and lightheadedness without a doctor's help.

"Lightheadedness needs to be distinguished from vertigo, which affects balance, and is the sensation that the individual or their surroundings are spinning," Dr. Fonarow says. While vertigo can be caused by inner ear infections, another type of inner ear condition — known as benign paroxysmal positional vertigo (BPPV) — is actually the most common cause, according to the American Academy of Family Physicians (AAFP).

BPPV is the result of an irregular clumping together of tiny calcium particles deep inside your ear, says AAFP. Normally these particles tell your brain in which direction to move your head. But if they become unevenly distributed, they can over-stimulate the nervous system, tricking your brain into thinking your head has moved when it hasn't. The good news: BBPV is easily diagnosed and treated through a series of head exercises that can help get the particles redistributed.

If you have diabetes, it's important to be on the lookout for signs of dizziness and lightheadedness. These are the hallmarks of hypoglycemia, which is when your blood sugar falls too low, below 70 mg/dL, according to the National Institute of Diabetes and Digestive and Kidney Diseases. The most common causes of hypoglycemia are skipping a meal, mis-dosing insulin and excessive exercise, says Mayo Clinic.

But anyone can experience low blood sugar under certain circumstances. Some medications can trigger a drop in blood sugar, as can excessive alcohol consumption, Mayo Clinic points out.

When blood sugar levels drop too low, a rapid spike in adrenaline gets underway, explains the American Diabetes Association (ADA). That, in turn, can trigger a wide array of warning signs, including shakiness, sweating, headache, irritability and, yes, lightheadedness.

The remedy is quickly downing a high-sugar drink like juice or eating a piece of candy or a glucose tablet, says ADA. This should both right your blood sugar levels and alleviate the dizziness.