As of Wednesday, April 17, 2013
DEAR DOCTOR K: I often feel lightheaded when I stand up, especially first thing in the morning. Why does this happen?
DEAR READER: You are probably experiencing a drop in blood pressure when you stand up. This is called orthostatic hypotension. As a result, not enough blood reaches your brain, and you feel lightheaded or dizzy.
When you stand up, gravity pulls the blood down. This causes blood to pool in the lower half of our bodies and blood pressure to drop. If it drops enough, you’ll have symptoms. Sensors in your major arteries signal your brain that your blood pressure has dropped. In response, the brain tells the heart to beat a little faster and stronger and blood vessels to constrict, which raises blood pressure. As a result, blood pressure and blood flow return more or less to normal.
But with age and certain medical conditions, these compensations may falter. The heart doesn’t pump as well. Blood vessels get stiffer and less responsive. The sensors in the arteries become less sensitive, and the signals they send less effective. As a result, some people experience sizable drops in blood pressure when they stand up. (I’ve put an illustration on my website, AskDoctorK.com.)
Here are some things you should try:
— Take your time standing up. Move gradually from lying down to sitting to a standing position. This is particularly important at night (when you go to the bathroom) or in the morning when you awaken. That’s when orthostatic hypotension is most likely.
— Try these maneuvers: Wiggle your toes and flex your feet before you stand up. This causes the muscles in your legs to squeeze more blood back up into your heart and to slightly raise blood pressure.
— Review your medications with your doctor and maybe make a change.
— Lift the head of your bed. Sleeping with your head higher than your feet keeps blood pressure higher. This causes your kidneys to release a hormone that increases blood pressure.
— Drink more fluids. Dehydration can cause blood pressure to drop.
— Perhaps increase your salt intake. Unless you have high blood pressure already, this is a good idea.
— Drink coffee in the morning. Caffeine boosts blood pressure.
— Exercise more. Improving your cardiovascular fitness through exercise may help the problem go away.
— Avoid straining. Straining to have a bowel movement or to pass urine (if you have an enlarged prostate) and coughing can cause blood pressure to briefly drop. Even laughing very hard can do it. Sometimes comedians really do leave the audience “rolling in the aisles.” When people start to get lightheaded from laughing hard, they instinctively get down on the floor to avoid falling.
— Wear compression stockings. Special stockings that apply pressure on the lower half of the body can keep blood from pooling in the leg veins. This, in turn, increases blood pressure.
Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.