Both low blood pressure and high blood pressure are linked to feelings of faintness, dizziness, or lightheadedness. People with low blood pressure commonly complain of dizziness because not enough oxygen is reaching the brain. Although rare, some patients who suffer from high blood pressure report feeling dizzy or a sensation of vertigo, in which objects appear to spin. Either instance of blood pressure and dizziness might induce faintness to the point of passing out.
Blood pressure that normally registers low, called hypotension, can create dizziness when someone rises suddenly from a prone or sitting position. This is referred to as postural or orthostatic hypotension prompted by a temporary drop in blood supply to the brain. Health experts believe these episodes are generally harmless and can be controlled by rising more slowly.
Certain medications used to control high blood pressure, or hypertension, might also produce lightheadedness. Alpha blockers prescribed to control the flow of blood during stressful situations may cause orthostatic hypotension when getting out of bed or rising from a sitting position. Dizziness occurs because the medication causes a momentary drop in blood pressure and interferes with the body’s normal adjustment of blood supply.
Low blood pressure produces other symptoms in some people including nausea, chest pain, sweating, and shortness of breath. Certain underlying illnesses, such as anemia or internal bleeding, may lower blood pressure and cause faintness. Dehydration from fever, vomiting, or excessive sweating elicits similar symptoms. Physicians aim to determine the exact reason for dizziness, which is challenging because different people describe the sensation differently.
High blood pressure and dizziness are considered a more serious health problem. Hypertension is called a "silent epidemic" because it rarely exhibits symptoms but affects millions of people worldwide and contributes to thousands of deaths each year. Usually, more than one drug is needed to effectively control dizziness and high blood pressure. Lifestyle and nutritional adaptations also help control hypertension.
The connection between blood pressure and dizziness is only one of several explanations for vertigo. Dizziness may also stem from a viral infection that affects the inner ear, which plays a vital role in balance. Low blood sugar can account for faintness but usually disappears after food is eaten. Other conditions that disrupt the supply of oxygen-rich blood to the brain include anxiety and panic attacks with hyperventilation.
Most cases involving blood pressure and dizziness are minor and resolve quickly. If lightheadedness leads to bouts of fainting, a doctor should be consulted. Dizziness accompanied by severe headaches and memory loss might signal a more serious medical condition, especially if there is a family history of epilepsy or diabetes. A loss of consciousness that re-occurs also requires medical attention.