Speaking in general, doctors try first to distinguish between neurologic (brain and nerves) and cardiovascular (heart and blood vessel) causes. Dizziness caused by neurologic illness is often associated with a sensation known as vertigo, which is a feeling of motion or spinning often accompanied by nausea. Vertigo itself has many causes, including benign problems of the inner ear and more serious conditions that affect the nerve that connects the ear to the brain and the brain itself. Vertigo is often reproduced by certain positions and may be associated with difficulty with balance, coordination, and posture.
Dizziness due to cardiovascular causes is often associated with lightheadedness, a sense of graying of the vision, and a feeling that you might pass out. Loss of consciousness in this setting is known as syncope. Dizziness from cardiovascular causes results from temporarily impaired blood flow to the brain, which may result either from low blood volume, impaired blood output from the heart, or an abnormal nerve reflex.
Low blood volume may be caused by either loss of blood cells (from bleeding, iron or vitamin deficiency, or impaired cell production), or by dehydration (from sweating, inadequate fluid intake, or excessive urination from uncontrolled diabetes). Dizziness due to these causes is often worsened by standing up quickly or standing for prolonged periods of time. Doctors can test for these conditions by measuring blood pressure in different positions, and checking the blood for red cell count, glucose, and electrolytes.
