Dizziness and Lightheadedness: What Causes It, and When to Check Your Arteries

Between 15 and 20 percent of adults report dizziness or vertigo in any given year, making it one of the most common reasons people seek medical care and one of the most frequently unresolved (Neuhauser, Handbook of Clinical Neurology, 2016). Most of it is the inner ear. Some of it is blood pressure. A smaller share is cardiovascular — and that share is the reason dizziness deserves a real workup rather than reassurance. This article separates the six causes, explains which ones a carotid duplex ultrasound or echocardiogram can settle, and gives you the red flags that change the timeline from "schedule something" to "go now."

Dizzy, Lightheaded, or Vertigo? The Distinction That Directs the Workup

The first question every clinician asks is "what do you mean by dizzy," and most patients find it impossible to answer. That is not a failure on your part — patients describe the same sensation different ways on the same day, and the description turns out to be a poor predictor of the underlying cause. Timing and triggers predict it far better.

Vertigo is the false sensation that you or the room is spinning or moving. It points strongly toward the vestibular system — the inner ear and its connections to the brainstem. Benign paroxysmal positional vertigo, vestibular neuritis, and Meniere's disease live here.

Lightheadedness is the sensation of being about to faint — a graying or narrowing of vision, a hollow feeling, sometimes a cold sweat. This one is far more likely to be circulatory. It means blood pressure or cardiac output dropped, briefly, below what your brain needed.

Disequilibrium is unsteadiness on the feet without any head sensation at all. It is common in older adults and usually multifactorial: neuropathy, vision, joint proprioception, medication.

This sorting determines which test comes first. Vertigo goes down the vestibular pathway; lightheadedness — especially with exertion — goes down the cardiovascular one. Getting that fork wrong is how people spend eighteen months in ENT waiting rooms with an undiagnosed valve problem.

What Causes Dizziness and Lightheadedness? The Six Categories

Nearly every cause of dizziness falls into one of six buckets. They are not equally common and not equally dangerous, and those two facts point in opposite directions — which is exactly why the workup is confusing.

1. Vestibular (inner ear)

The single largest group. Vestibular vertigo has a twelve-month prevalence of roughly 5 percent in adults and a lifetime prevalence near 8 percent (Neuhauser, 2016). Positional vertigo lasting seconds when you roll over in bed is the classic presentation. It is benign, treatable with repositioning maneuvers, and not what this article is about.

2. Orthostatic — blood pressure dropping on standing

Orthostatic hypotension affects roughly one in five community-dwelling adults over 60 (Journal of Gerontology, 2018). Standing pulls blood into the legs, and the autonomic system is supposed to clamp the vessels down within seconds to compensate. When it doesn't — dehydration, blood pressure medication, diabetic autonomic neuropathy, age — the brain is briefly underperfused and you feel it. Common, and often fixable by adjusting a medication.

3. Cardiac — rhythm or structure

The heart can cause dizziness two ways: a rhythm too fast or too slow to fill and eject properly, or a structural obstruction to outflow. Aortic stenosis is the structural one to know. It affects about 3 percent of people over 65 and up to 10 percent of those over 80, and its classic triad is angina, dizziness or syncope with exertion, and breathlessness. Dizziness from aortic stenosis is a marker of severe disease, not early disease. If you get lightheaded when you exert yourself, an echocardiogram is the correct next test — not a tilt table and not an MRI. Related reading: when palpitations warrant an echo.

4. Cerebrovascular — the arteries supplying the brain

Reduced flow through the carotid or vertebral arteries can produce dizziness, though it almost never does so in isolation. This is the category that carries the most consequence when missed, and the one addressed in detail below.

5. Metabolic and hematologic

Anemia, hypoglycemia, thyroid dysfunction, and electrolyte disturbance all reduce oxygen delivery or disturb autonomic regulation. This is the category standard bloodwork actually does cover, which is why bloodwork is a reasonable first step — and why a normal panel should move the workup forward rather than end it.

6. Medication effect

Antihypertensives, diuretics, alpha blockers, nitrates, antidepressants, sedatives, and several antiarrhythmics all list dizziness. In older adults on five or more medications, this is frequently the whole answer. Bring the actual bottles, not a remembered list.

When Dizziness Points to the Arteries in Your Neck

Here is the honest version, because the internet gets this wrong in both directions.

Isolated dizziness — dizziness alone, with a normal neurological exam and no other symptom — is a poor predictor of stroke. In a population-based study published in Stroke, stroke or TIA was diagnosed in 3.2 percent of all emergency department patients presenting with dizziness, vertigo, or imbalance, but in only 0.7 percent of those with isolated dizziness (Kerber et al., 2006). Isolated dizziness argues for a non-cerebrovascular cause, not against it. A more recent systematic review pooled stroke prevalence across emergency department dizziness presentations at around 5.5 percent, with wide variation by how aggressively the cohorts were imaged.

What flips that calculation is company. Dizziness with slurred speech, double vision or visual field loss, facial asymmetry, one-sided weakness or numbness, severe unsteadiness, or a new severe headache is a categorically different presentation — those warrant emergency evaluation, not a scheduled scan. If you have had an episode like that and it resolved, read what a TIA actually means. The resolution is not reassurance.

For most people reading this, the more useful question is not "is this dizziness a stroke" but "while I am investigating this, do I have carotid disease I don't know about." That second question has a straightforward answer. Asymptomatic carotid stenosis is present in about 4.2 percent of the general population above the 50 percent threshold and 1.7 percent above 70 percent, rising with age to 7.5 percent of men over 80 (de Weerd et al., Stroke, 2010). Most of those people have no idea. Read more on how carotid plaque develops silently.

What a Carotid Duplex Ultrasound Actually Measures

A carotid duplex is two exams running at once. B-mode grayscale imaging shows the artery wall and any plaque directly; Doppler measures how fast blood is moving through it. Together they answer a question a stethoscope and an exam cannot.

Plaque burden and character. The scan visualizes plaque in the common and internal carotid arteries, measures its thickness, and characterizes it as calcified, soft, or heterogeneous. Soft, irregular plaque carries different embolic risk than dense calcified plaque of the same size.

Degree of stenosis. Narrowing is graded from peak systolic velocity, end-diastolic velocity, and the ratio between internal and common carotid velocities. A peak systolic velocity at or above 200 cm per second identifies 70 percent or greater stenosis with approximately 90 percent sensitivity and 94 percent specificity against angiography (Jahromi et al., Journal of Vascular Surgery, 2005). That is the accuracy that makes duplex the accepted first-line test rather than a screening curiosity.

Vertebral artery flow and direction. This is the part directly relevant to dizziness. The vertebral arteries supply the brainstem and cerebellum — the structures that generate balance. The duplex confirms the vertebrals are patent and, critically, that flow is antegrade. Retrograde vertebral flow is the signature of subclavian steal, in which a proximal subclavian stenosis siphons blood backward down the vertebral artery to supply the arm. Its classic symptom is dizziness brought on by using that arm.

Intima-media thickness. Wall thickness in the common carotid is a marker of early atherosclerosis, often abnormal well before any stenosis exists — a reading of arterial age rather than a diagnosis.

When the Dizziness Is Coming From the Heart

Three features separate cardiac lightheadedness from everything else, and patients consistently under-report all three because they seem unrelated.

It happens during exertion, not after standing. Orthostatic dizziness occurs in the seconds after you stand up and resolves when you sit. Cardiac dizziness occurs at the top of the stairs, partway up a hill, carrying groceries. That distinction points at outflow obstruction or an exercise-induced arrhythmia and is the single most useful piece of history in this entire workup.

It comes with palpitations, chest pressure, or breathlessness. Any of those three alongside dizziness moves cardiac causes to the front of the line. If you are also short of breath climbing stairs, the two symptoms are likely the same problem.

It is abrupt, with no warning and no trigger. Reflex and orthostatic causes usually give a few seconds of prodrome. An arrhythmia often does not. Sudden dizziness with no prodrome, and especially any episode of true loss of consciousness, needs cardiac evaluation.

An echocardiogram addresses all three: aortic valve gradient and area, left ventricular function and ejection fraction, hypertrophy and outflow tract obstruction, and the other valves. An EKG records about ten seconds of electrical activity and says nothing about structure. Both have a role; only one images the heart.

Red Flags: When Dizziness Is an Emergency

Call 911 — do not drive, do not wait for an appointment — if dizziness arrives with any of these:

Any sudden neurological sign. Slurred speech, facial droop, one-sided weakness or numbness, double vision, or sudden loss of part of your visual field. These are stroke symptoms whether or not the dizziness is the loudest part.

Inability to walk or sit unsupported. Severe gait instability with acute dizziness is one of the strongest predictors of a cerebellar cause. Being unable to stand without falling toward one side is a red flag even when everything else looks normal.

Sudden severe headache or neck pain with the dizziness. This combination can indicate arterial dissection, particularly in younger patients and after neck trauma or manipulation.

Chest pain, or fainting with no warning. Syncope with no prodrome, or any dizziness with chest pressure, is cardiac until proven otherwise.

Short of those, recurrent dizziness in an adult with vascular risk factors is not an emergency — it is an investigation. The mistake is never finishing it. Anyone with long-standing high blood pressure, diabetes, high cholesterol, or a smoking history is exactly who the vascular workup is worth completing for.

Who Should Get Vascular Imaging for Dizziness?

Imaging is not indicated for every dizzy person. Textbook positional vertigo lasting ten seconds in a healthy 32-year-old does not need a carotid scan. These profiles do.

Age over 55 with two or more vascular risk factors. High blood pressure, diabetes, high cholesterol, current or former smoking, or a family history of stroke. Carotid stenosis prevalence in this group is meaningfully above baseline, and the scan answers a risk question independent of the dizziness.

Dizziness triggered by arm use. Dizziness while reaching overhead, painting a ceiling, or carrying something on one side raises the question of subclavian steal, which duplex identifies directly through vertebral flow direction and bilateral arm pressures.

Lightheadedness with exertion. Echocardiogram first, to assess the aortic valve and ventricular function. Carotid duplex is reasonable alongside it in anyone with vascular risk factors.

A prior TIA or stroke. Any new or recurrent dizziness in someone with cerebrovascular history warrants re-imaging the carotids. Read what your carotid arteries signal before a stroke.

A complete workup that found nothing. If bloodwork, EKG, and neurological exam were all normal and the dizziness persists, the structures that have not been looked at are the valves, the pump, and the neck arteries. Imaging them is the logical next step, not a redundant one.

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