Usually dizziness is a result of low blood flow to and/or low oxygenation in the brain. It is for this reason that you are told to get horizontal or put your head between your legs/lower than your heart position to increase the blood flow and oxygenation to the brain if you become dizzy.
There are many ways to become dizzy. Some examples are:
- If you lie down for a while, and then quickly get up, and start moving around, it may cause temporary dizziness from hypotension (this is called orthostatic hypotension).
- Becoming intoxicated from alcohol or drugs in some drug classes (such as narcotics) will make you dizzy for the remainder of the intoxication/drug action. Both of these are due to central nervous system depression.
- Heart failure or other Heart disease and circulatory insufficiency can cause dizziness.
- Vasovagal response is the most common cause of dizziness and syncope (passing out), it is an autonomic nervous system problem related to the vagus nerve.
- Breathing noxious fumes or other gases that disrupt the oxygen content in your blood can make you dizzy.
- You can become dizzy from dehydration or other causes of low blood volume such as blood loss.
- Decreased blood flow to the brain can also be caused by blood vessel constrictions or obstructions, especially in the carotid arteries that supply the head with oxygenated blood.
