Overview: Light-headedness is a feeling as though you might faint.
Light-headedness is a feeling of faintness. Everyone has experienced it. It is caused by insufficient blood in the brain. It is a very common symptom for HCM patients.
One source of confusion is that we often use the word "dizzy," which can mean light-headed but it can also describe a feeling of imbalance or vertigo, like when children deliberately spin around. We have all had this experience too - and it is different from light-headedness. Vertigo is caused by the inner ear. Of course it's possible to have both light-headedness and vertigo at the same time, but it doesn't happen very often.