There are a number of causes of dizziness.

Sudden low blood pressure (orthostatic or postural hypotension)

A sudden drop in blood pressure when you sit up or stand up is called orthostatic hypotension.

Normally, when you stand quickly, your nerves and arteries work together to counteract the force of gravity and keep your blood evenly distributed throughout your body. Your heart beats faster, your arteries narrow, more blood circulates, and blood pressure stabilizes. But many conditions and medications common in older people can interrupt this natural process. This can cause a sudden drop in your systolic blood pressure (the upper number in your blood pressure reading).

With orthostatic hypotension, gravity makes your blood collect in your legs when you sit up or stand up quickly after sitting or lying down. For a short time period, there isn’t enough blood to flow to your heart, your brain, and the rest of your body. This kind of low blood pressure causes lightheadedness within three minutes of sitting up or standing. It lasts from a few seconds to several minutes. Along with the feeling of faintness, you may feel nauseated and have pale or clammy skin.

Examples of some conditions that can bring on sudden low blood pressure include:

  • Dehydration can be caused by not drinking enough fluids, fever, diarrhea, vomiting, medications such as diuretics (water pills), or very hot weather.
  • Heart problems such as heart failure, atherosclerosis, heart attack, slow heart rate (bradycardia), or heart valve problems.
  • Diabetes, which can cause frequent urination or nerve damage if uncontrolled.
  • Nervous system disorders such as Parkinson's disease.

Sudden low blood pressure can also be caused by long-term bed rest, age-related nerve problems, anemia (not enough red blood cells), or incorrect feedback from the nerves in your body. Certain medications such as anti-Parkinsonian drugs, some anti-depressants, and medications for erectile dysfunction can also cause orthostatic hypotension. Taking certain blood pressure medications can also affect your body’s response to sitting or standing up.  

Anxiety Disorders

Lightheadedness can also be linked to feelings of anxiety, especially panic attacks, hyperventilation, and other severe emotional states.

Lightheadedness or "Near Fainting" (Presyncope)

Sudden lightheadedness or feelings of faintness without losing consciousness is called presyncope.  It happens to older people quite often and can be associated with chronic physical conditions such as heart disease or diabetes. Because these feelings can bring on a fall, it’s important to be promptly evaluated if you feel faint or lightheaded.


Last Updated December 2020