Athletes and other very fit people may feel dizzy when they rise from lying to standing because of their slow pulse rates. Exercise makes your heart stronger so it can pump more blood with each beat and it doesn't have to beat as often. A slow pulse rate can be good. Since your heart doesn't beat as often, it has more time to rest between beats. Like a low-mileage used car, perhaps this will mean it takes longer to wear out. But a slow heart rate can make you dizzy when you change position.

When you raise yourself from lying to sitting, or from sitting to standing, the force of gravity pulls blood down from your brain towards your feet and your blood can't get back to your brain until your next heart beat. If you have a pulse rate of only 50 beats a minute, it will take more than a second between beats. That can be enough time for your brain to suffer briefly from a lack of oxygen, so you feel dizzy. You can even pass out while you wait for your next heartbeat to come along and pump blood back up to your brain.

Dizziness can also be a sign of an irregular heartbeat or blocked arteries leading to your brain, so people who feel dizzy when they get up should check with their doctors. However, if all tests are negative and you are very fit, chances are that you have a strong athletic heart with a slow rate, and all you need to do is remember to get up slowly.

If you develop dizziness that lasts for more than a few seconds, be sure to check with your doctor; it could be a stroke. Recurrent dizziness can be caused by temporary interruption of circulation to your brain, such as blocked neck arteries or an irregular heart beat. It can be caused by a stroke, tumors on the hearing nerve or brain, drug reactions, a bang on the head, an infection in the inner ear or anything that interferes with nerve function such as lack of vitamin B12, diabetes, migraine, seizures or infections such as herpes or chicken pox.

Dizziness can be caused by debris in your balance apparatus in your inner ear, called benign positional vertigo, which can be cured by special rapid movements of the head.

Dizziness lasting for a day or longer is usually due to nerve damage called neuritis and often gets better without treatment; or to a stroke which often does not get better and is associated with reduced vision. If you have any reason to think that your dizziness may be the symptom of a stroke, you must seek treatment immediately because shutting off the blood supply to a part of your brain called the cerebellum can cause progressive swelling and permanent damage or death if it is not treated immediately.

Dizziness lasting for minutes or a few hours can be due to temporary obstruction of the blood supply to the brain called transient ischemic attacks, migraine or seizures. If it continues or recurs, it is often due to Meniere's syndrome which includes reduced hearing, ringing in the ears and a feeling of pressure in the ears. Meniere's syndrome is treated with rest and probably a prescription for scopolamine. Your doctor may also try antihistamines such as cyclizine or meclizine, tranquilizers such as Valium, anticonvulsants such as Dilantin, or migraine medications such as Imitrex. If your dizziness and other symptoms are severe enough, your doctor may give you a drug to damage your hearing nerve permanently.