Dizziness and giddiness are words used to describe a wide variety of sensations that most of us have experienced. It can often be difficult to distinguish between true dizziness (vertigo) and other problems.
In true vertigo there is usually a feeling of spinning and unsteadiness. The affected person thinks they are going to fall over — something that may well happen. However, with vertigo if you fall over you generally don't ‘black out’ — lose consciousness. Vertigo may occur as a result of a number of problems affecting the inner ear, where the body's delicate balancing mechanism is situated.
One of the most common reasons that people might suddenly feel ‘dizzy’ is when there is a temporary reduction of blood flow to the brain. Brain cells are very sensitive to the oxygen carried in the bloodstream and react quickly when their oxygen supply is reduced or cut off. This kind of dizziness is more a feeling of faintness, the feeling that you are about to black out. The medical word for fainting (also described as blacking out or passing out) is syncope, and the feeling of being about to faint is called pre-syncope.
This often happens when someone gets up suddenly, particularly if they have been sitting or lying down for quite a long time.
Under these circumstances there can be a sudden fall in blood pressure — known as postural hypotension — which in turn leads to reduced oxygen to the brain. This will lead to a feeling of unsteadiness and even fainting. The feeling is usually very short-lived, as the body's capacity to correct the low blood pressure quickly clicks into action.
Those who experience postural hypotension quickly learn the knack of getting up slowly. When they wake up in the morning they should sit on the side of the bed for a few moments before rushing out to get the paper.
Other causes of light-headedness include anaemia, some heart conditions, partially blocked arteries (atherosclerosis) and anxiety disorders.
If you experience faintness outside of expected situations (for example, getting up quickly from sitting or lying on a hot day), or if there are other symptoms associated with it, such as palpitations, nausea or chest discomfort, you should see your doctor.
2. NHS Choices. Dizziness (lightheadedness) (updated 16 Jan 2013). http://www.mayoclinic.com/health/dizziness/DS00435 (accessed May 2013).