What can constant dizziness be from? i had an ekg, bp, and vitamin deficiency tests, all normal. it's a faint feeling and sometimes a sudden spinning.

Vertigo?: Dizziness associated with the sensation of spinning generally is referred to as vertigo. Vertigo is divided into central vertigo and peripheral vertigo. A common cause of peripheral vertigo is inner ear infection, which is usually viral and self-limited. Central vertigo can be more complex, including serous problems like brain tumors. Some medications cause vertigo.

Merits another look: We try to distinguish between vertigo (spinning) and lightheadedness or "faint feeling". Vertigo often is caused by a problem with the semicircular canals in the inner ear; lightheadedness often is the result of dehydration and other causes of a low blood pressure, typically upon standing. Checking ones BP sitting and standing can detect the low BP and it responds to an increase in fluids.